Three axis magnetic field sensor

Abstract

Three bridge circuits (101, 111, 121), each include magnetoresistive sensors coupled as a Wheatstone bridge (100) to sense a magnetic field (160) in three orthogonal directions (110, 120, 130) that are set with a single pinning material deposition and bulk wafer setting procedure. One of the three bridge circuits (121) includes a first magnetoresistive sensor (141) comprising a first sensing element (122) disposed on a pinned layer (126), the first sensing element (122) having first and second edges and first and second sides, and a first flux guide (132) disposed non-parallel to the first side of the substrate and having an end that is proximate to the first edge and on the first side of the first sensing element (122). An optional second flux guide (136) may be disposed non-parallel to the first side of the substrate and having an end that is proximate to the second edge and the second side of the first sensing element (122).

The invention claimed is: 
     
       1. A ferromagnetic thin-film based magnetic field sensor comprising:
 a substrate having a planar surface; and   a first magnetoresistive sensor comprising:
 a first sensing element having a first side lying parallel to the planar surface of the substrate, the first sensing element having a second side opposed to the first side and having first and second opposed edges; and 
 a first flux guide comprising a soft ferromagnetic material disposed non-parallel to the first side of the first sensing element and having an end that is proximate to the first edge and the first side of the first sensing element. 
   
     
     
       2. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first magnetoresistive sensor further comprises:
 a second flux guide comprising a soft ferromagnetic material disposed non-parallel to the first side of the first sensing element and having an end that is proximate to the second edge and the second side of the first sensing element. 
 
     
     
       3. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first magnetoresistive sensor comprises one of an array of ferromagnetic thin-film based magnetic field sensors. 
     
     
       4. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first flux guide comprises a high aspect ratio structure non-parallel to the first sense element. 
     
     
       5. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first flux guide comprises a U shaped element. 
     
     
       6. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first flux guide includes a flared end. 
     
     
       7. The ferromagnetic thin-film based magnetic field sensor of  claim 1  further comprising a material disposed adjacent the first flux guide and comprising one of the group consisting of a high conductivity metal and a dielectric material. 
     
     
       8. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein the first flux guide comprises a box shaped structure. 
     
     
       9. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein at least one of the first and second flux guides is disposed substantially orthogonal to the plane of the substrate. 
     
     
       10. The ferromagnetic thin-film based magnetic field sensor of  claim 1  wherein at least one of the first and second flux guides is disposed at an angle of between 45 degrees and 90 degrees to the plane of the substrate. 
     
     
       11. The ferromagnetic thin-film based magnetic field sensor of  claim 1  further comprising:
 a second magnetoresistive sensor having a second sensing element for detecting a magnetic field in a second direction orthogonal to the first direction; and 
 a third magnetoresistive sensor having a third sensing element orthogonal to the second sensing element for detecting a magnetic field in a third direction orthogonal to the first and second directions, 
 wherein the third sensing element is in a plane with the first and second sensing elements. 
 
     
     
       12. The ferromagnetic thin-film based magnetic field sensor of  claim 11 , wherein the first, second, and third sensor elements each comprise an imbalanced synthetic antiferromagnet formed with first and second ferromagnetic layers separated by a spacer layer, where the first and second ferromagnetic layers have different magnetic moments. 
     
     
       13. The ferromagnetic thin-film based magnetic field sensor of  claim 1  further comprising:
 the first magnetoresistive sensor comprising:
 a first pinned layer; 
 
 a second magnetoresistive sensor comprising:
 a second pinned layer; and 
 a second sensing element formed on the second pinned layer; 
 
 a third magnetoresistive sensor comprising:
 a third pinned layer; and 
 a third sensing element formed on the third pinned layer and orthogonal to the second sensing element; 
 wherein the second and third pinned layers are oriented about 45 degrees to the first pinned layer. 
 
 
     
     
       14. The ferromagnetic thin-film based magnetic field sensor of  claim 13  wherein the first magnetic tunnel junction further comprises:
 a second flux guide disposed non-parallel to the first side of the first sensing element and having an end that is proximate to the second edge and the second side of the first sensing element. 
 
     
     
       15. The ferromagnetic thin-film based magnetic field sensor of  claim 14  wherein the first and second flux guides each comprise an aspect ratio greater than 10. 
     
     
       16. A ferromagnetic thin-film magnetic field sensor comprising:
 a first bridge circuit comprising first, second, third, and fourth magnetic tunnel junction sensors coupled as a Wheatstone bridge for sensing a magnetic field orthogonal to the plane of the sensors;   the first magnetic tunnel junction sensor comprising:
 a first reference layer; and 
 a first sensing element formed on the first reference layer, the first sensing element having first and second edges and first and second sides; and 
 a first flux guide comprising a soft ferromagnetic material disposed orthogonal to and spaced from the first edge and the first side of the first sensing element; 
   the second magnetic tunnel junction sensor comprising:
 a second reference layer; and 
 a second sensing element formed on the second reference layer, the second sensing element having first and second edges and first and second sides; and 
 a second flux guide comprising a soft ferromagnetic material disposed orthogonal to and spaced from the first edge and the first side of the second sensing element; 
   the third magnetic tunnel junction sensor comprising:
 a third reference layer; and 
 a third sensing element formed on the third reference layer, the third sensing element having first and second edges and first and second sides; and 
 a third flux guide comprising a soft ferromagnetic material disposed orthogonal to and spaced from the first edge and the first side of the third sensing element; 
   the fourth magnetic tunnel junction sensor comprising:
 a fourth reference layer; and 
 a fourth sensing element formed on the fourth reference layer, the fourth sensing element having first and second edges and first and second sides; and 
 a fourth flux guide disposed orthogonal to and spaced from the first edge and the first side of the fourth sensing element. 
   
     
     
       17. The ferromagnetic thin-film based magnetic field sensor of  claim 16  wherein the first, second, third, and fourth magnetic tunnel junction sensors further comprise fifth, sixth, seventh, and eighth flux guides disposed orthogonal to and spaced from the second edge and the second side of the first, second, third, and fourth sensing elements, respectively. 
     
     
       18. The ferromagnetic thin-film based magnetic field sensor of  claim 16  further comprising:
 a second bridge circuit comprising fifth, sixth, seventh, and eighth magnetic tunnel junction sensors coupled as a second Wheatstone bridge for sensing a magnetic field in a second direction orthogonal to the first direction; and 
 a third bridge circuit comprising, ninth, tenth, eleventh, and twelfth magnetic tunnel junction sensors coupled as a third Wheatstone bridge for sensing a magnetic field in a third direction orthogonal to the first and second directions. 
 
     
     
       19. The ferromagnetic thin-film based magnetic field sensor of  claim 16  wherein each of the first, second, third, and fourth sensors comprises an array of sense elements. 
     
     
       20. A method of testing the functionality and sensitivity of a response of the Z axis of a ferromagnetic thin-film magnetic field sensor including a substrate having a planar surface, and a first magnetoresistive sensor comprising a sensing element having a first side lying parallel to the planar surface of the substrate, the sensing element having a second side opposed to the first side and having first and second opposed edges, a first flux guide comprising a soft ferromagnetic material disposed non-parallel to the first side of the substrate and having an end that is proximate to the first edge and the first side of the sensing element, and a metal line formed adjacent contiguous to the flux guide, the method comprising:
 applying a current through the metal line to provide a magnetic field with a component parallel to the plane of the flux guides.   
     
     
       21. The method of  claim 20 , further comprising:
 applying a current pulse through the metal line to reset the flux guide domain structure.   
     
     
       22. A ferromagnetic thin-film based magnetic field sensor comprising:
 a first plurality of magnetoresistive sensors coupled to sense a magnetic field in a first direction orthogonal to a plane of the first plurality of magnetoresistive sensors, wherein the first plurality of magnetoresistive sensors includes first, second, third, and fourth magnetoresistive sensors;   the first magnetoresistive sensor comprising:
 a first sensing element, and 
 a first flux guide comprising a first soft ferromagnetic material, wherein the first soft ferromagnetic material is a first high permeability magnetic material, wherein (i) the first flux guide is above or below the first sensing element of the first magnetoresistive sensor in the first direction, (ii) the first flux guide is disposed non-parallel to a first side of the first sensing element, and (iii) the first flux guide includes an end that is proximate to a first edge and on the first side of the first sensing element; 
   the second magnetoresistive sensor comprising:
 a second sensing element, and 
 a second flux guide comprising a second soft ferromagnetic material, wherein the second soft ferromagnetic material is a second high permeability magnetic material, wherein (i) the second flux guide is above or below the second sensing element of the second magnetoresistive sensor in the first direction, (ii) the second flux guide is disposed non-parallel to a first side of the second sensing element, and (iii) the second flux guide includes an end that is proximate to and on the first side of the second sensing element; 
   the third magnetoresistive sensor comprising:
 a third sensing element, and 
 a third flux guide comprising a third soft ferromagnetic material, wherein the third soft ferromagnetic material is a third high permeability magnetic material, wherein (i) the third flux guide is above or below the third sensing element of the third magnetoresistive sensor in the first direction, (ii) the third flux guide is disposed non-parallel to a first side of the third sensing element, and (iii) the third flux guide includes an end that is proximate to and on the first side of the third sensing element; and 
   the fourth magnetoresistive sensor comprising:
 a fourth sensing element, and 
 a fourth flux guide comprising a fourth soft ferromagnetic material, wherein the fourth soft ferromagnetic material is a fourth high permeability magnetic material, wherein (i) the fourth flux guide is above or below the fourth sensing element of the fourth magnetoresistive sensor in the first direction, (ii) the fourth flux guide is disposed non-parallel to a first side of the fourth sensing element, and (iii) the fourth flux guide includes an end that is proximate to and on the first side of the fourth sensing element, 
   wherein the sensor further includes a plurality of cladded lines, wherein each cladded line is positioned adjacent to one of the first, second, third, and fourth flux guides,   wherein each flux guide of the first, second, third, and fourth flux guides includes (i) a first vertical segment, (ii) a second vertical segment, and (iii) a horizontal segment connecting the first and second vertical segments, wherein a free end of the first vertical segment is flared away from a free end of the second vertical segment, each flux guide having the flared-away free ends at least partially enclosing the cladded line between the two vertical segments, and wherein the first vertical segment, the second vertical segment, and the horizontal segment define an opening, the opening having a width defined by a distance between inner walls of the first and second vertical segments, wherein the width of the opening between the inner walls at the flare-away free ends is larger than the width of the opening between the inner walls at connected ends of the first and second vertical segments, the first and second vertical segments being connected to the horizontal segment at the connected ends.    
     
     
       23. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth high permeability magnetic materials is the same material.  
     
     
       24. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein at least one of the first, second, third, and fourth high permeability magnetic materials is nickel iron (NiFe).  
     
     
       25. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth high permeability magnetic materials is nickel iron (NiFe).  
     
     
       26. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit includes input terminals configured to receive an electrical power and output terminals connected to a voltage meter.  
     
     
       27. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit is configured to detect the magnetic field in the first direction.  
     
     
       28. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first plurality of magnetoresistive sensors is connected into a bridge circuit having input terminals and output terminals.  
     
     
       29. The ferromagnetic thin-film based magnetic field sensor of claim 28, wherein the input terminals are configured to receive electrical power and the output terminals are connected to a voltmeter to measure an output signal.  
     
     
       30. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected for differential measurement.  
     
     
       31. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected to, in operation, subtract resistances of the first and second magnetoresistive sensors.  
     
     
       32. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected to, in operation, produce a response when sensing a magnetic field in a second direction orthogonal to the first direction.  
     
     
       33. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected to, in operation, eliminate a magnetic field response in a second direction orthogonal to the first direction.  
     
     
       34. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and second magnetoresistive sensors are connected to, in operation, double a magnetic field measurement in the first direction.  
     
     
       35. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth magnetoresistive sensors is a magnetic tunnel junction sensor.  
     
     
       36. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the ferromagnetic thin-film based magnetic field sensor is configured to generate a sensor signal, and wherein the magnetic field in the first direction is determined based on the sensor signal.  
     
     
       37. The ferromagnetic thin-film based magnetic field sensor of claim 22, further comprising:
 a second plurality of magnetoresistive sensors configured to be electrically connected together to sense a magnetic field in a second direction orthogonal to the first direction.    
     
     
       38. The ferromagnetic thin-film based magnetic field sensor of claim 22, further comprising:
 a second plurality of magnetoresistive sensors configured to be electrically connected together to sense a magnetic field in a second direction orthogonal to the first direction; and   a third plurality of magnetoresistive sensors configured to be electrically connected together to sense a magnetic field in a third direction orthogonal to the first and second directions.    
     
     
       39. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first magnetoresistive sensor further includes a first reference layer, the second magnetoresistive sensor further includes a second reference layer, the third magnetoresistive sensor further includes a third reference layer, and the fourth magnetoresistive sensor further includes a fourth reference layer.  
     
     
       40. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein at least one of the first, second, third, and fourth flux guides is configured as a bar.  
     
     
       41. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein the first and third flux guides are above the first and third sensing elements, respectively, and wherein the second and fourth flux guides are below the second and fourth sensing elements, respectively.  
     
     
       42. The ferromagnetic thin-film based magnetic field sensor of claim 22, wherein each of the first, second, third, and fourth sensing elements includes a second side opposite to the first side, and wherein the first and third flux guides are above the first sides of the first and third sensing elements, respectively, and wherein the second and fourth flux guides are below the second sides of the second and fourth sensing elements, respectively.  
     
     
       43. A ferromagnetic thin-film based magnetic field sensor comprising:
 a first plurality of magnetoresistive sensors coupled together, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors comprises in an order in a direction:
 a reference layer, 
 an intermediate layer, and 
 a sensing element; and 
   one or more flux guides, wherein each flux guide of the one or more flux guides includes a soft ferromagnetic material, wherein the soft ferromagnetic material is a high permeability magnetic material, wherein at least one flux guide of the one or more flux guides is associated with at least one magnetoresistive sensor of the first plurality of magnetoresistive sensors, and wherein (i) the at least one flux guide is in a plane that is above or below the at least one magnetoresistive sensor and parallel to the sensing element of the at least one magnetoresistive sensor, (ii) the at least one flux guide is disposed non-parallel to a first side of the at least one magnetoresistive sensor, and (iii) the at least one flux guide includes an end that is proximate to a first edge and on the first side of the at least one magnetoresistive sensor,   wherein the sensor further includes a plurality of cladded lines, wherein each cladded line is positioned adjacent to a flux guide of the one or more flux guides,   wherein each flux guide of the one or more flux guides includes (i) a first vertical segment, (ii) a second vertical segment, and (iii) a horizontal segment connecting the first and second vertical segments, and wherein a free end of the first vertical segment is flared away from a free end of the second vertical segment, each flux guide having the flared-away free ends at least partially enclosing the cladded line between the two vertical segments, and wherein the first vertical segment, the second vertical segment, and the horizontal segment define an opening, the opening having a width defined by a distance between inner walls of the first and second vertical segments, wherein the width of the opening between the inner walls at the flare-away free ends is larger than the width of the opening between the inner walls at connected ends of the first and second vertical segments, the first and second vertical segments being connected to the horizontal segment at the connected ends.    
     
     
       44. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors is a magnetic tunnel junction sensor.  
     
     
       45. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the intermediate layer is an insulating dielectric layer.  
     
     
       46. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor,
 wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, and a fourth flux guide, and   wherein the first flux guide is associated with the first magnetoresistive sensor, the second flux guide is associated with the second magnetoresistive sensor, the third flux guide is associated with the third magnetoresistive sensor, and the fourth flux guide is associated with the fourth magnetoresistive sensor.    
     
     
       47. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor,
 wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, and a fourth flux guide, and   wherein the first flux guide is above the first magnetoresistive sensor, the second flux guide is below the second magnetoresistive sensor, the third flux guide is above the third magnetoresistive sensor, and the fourth flux guide is below the fourth magnetoresistive sensor.    
     
     
       48. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor, each of the first, second, third, and fourth magnetoresistive sensors including a first side and a second side opposite to the first side,
 wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, a fourth flux guide, a fifth flux guide, a sixth flux guide, a seventh flux guide, and an eighth flux guide, and   wherein the first flux guide is below the first side of first magnetoresistive sensor, the second flux guide is above the second side of the first magnetoresistive sensor, the third flux guide is above the first side of the second magnetoresistive sensor, the fourth flux guide is below the second side of the second magnetoresistive sensor, the fifth flux guide is below the first side of the third magnetoresistive sensor, the sixth flux guide is above the second side of the third magnetoresistive sensor, the seventh flux guide is above the first side of the fourth magnetoresistive sensor, and the eighth flux guide is below the second side of the fourth magnetoresistive sensor.    
     
     
       49. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the high permeability magnetic material is nickel iron (NiFe).  
     
     
       50. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected for differential measurement.  
     
     
       51. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, subtract resistances of the first and second magnetoresistive sensors.  
     
     
       52. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, produce a response when sensing a magnetic field in a second direction orthogonal to the direction.  
     
     
       53. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, eliminate a magnetic field response in a second direction orthogonal to the direction.  
     
     
       54. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, double a magnetic field measurement in the direction.  
     
     
       55. The ferromagnetic thin-film based magnetic field sensor of claim 43, further comprising:
 a second plurality of magnetoresistive sensors configured to be electrically connected together, wherein the first plurality of magnetoresistive sensors is configured to sense a first magnetic field in the direction, and wherein the second plurality of magnetoresistive sensors is configured to sense a second magnetic field in a second direction orthogonal to the direction.    
     
     
       56. The ferromagnetic thin-film based magnetic field sensor of claim 43, further comprising:
 a second plurality of magnetoresistive sensors configured to be electrically connected together; and   a third plurality of magnetoresistive sensors configured to be electrically connected together,   wherein the first plurality of magnetoresistive sensors is configured to sense a first magnetic field in the direction, the second plurality of magnetoresistive sensors is configured to sense a second magnetic field in a second direction orthogonal to the direction, and the third plurality of magnetoresistive sensors is configured to sense a magnetic field in a third direction orthogonal to the direction and the second direction.    
     
     
       57. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit is configured to detect a magnetic field in the direction.  
     
     
       58. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit includes input terminals configured to receive an electrical power and output terminals connected to a voltage meter.  
     
     
       59. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the first plurality of magnetoresistive sensors is connected into a bridge circuit having input terminals and output terminals.  
     
     
       60. The ferromagnetic thin-film based magnetic field sensor of claim 59, wherein the input terminals are configured to receive electrical power and the output terminals are connected to a voltmeter to measure an output signal.  
     
     
       61. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the order in the direction includes:
 the sensing element of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated intermediate layer of each magnetoresistive sensor, and   the intermediate layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated reference layer of each magnetoresistive sensor.    
     
     
       62. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the order in the direction includes:
 the reference layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated intermediate layer of each magnetoresistive sensor, and   the intermediate layer of each magnetoresistive sensor of the first plurality of magnetoresistive sensors being formed on or above the associated sensing element of each magnetoresistive sensor.    
     
     
       63. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes a plurality of layers having a combined thickness in a range of 10 to 1000 Å.  
     
     
       64. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes a plurality of layers having a combined thickness in a range of 250 to 350 Å.  
     
     
       65. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the sensing element includes a thickness in a range of 10 to 5000 Å.  
     
     
       66. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the sensing element includes a thickness in a range of 10 to 60 Å.  
     
     
       67. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the ferromagnetic thin-film based magnetic field sensor is configured to generate a sensor signal, and wherein a magnetic field in the direction is determined based on the sensor signal.  
     
     
       68. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes:
 a ferromagnetic layer; and   an antiferromagnetic layer.    
     
     
       69. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes:
 a ferromagnetic layer having a thickness in a range of 20 to 80 Å; and   an antiferromagnetic layer having a thickness of approximately 200 Å.    
     
     
       70. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes:
 a ferromagnetic layer; and   an antiferromagnetic layer including iridium-manganese (IrMn) alloy or platinum-manganese (PtMn) alloy.    
     
     
       71. The ferromagnetic thin-film based magnetic field sensor of claim 43, wherein the reference layer of each magnetoresistive sensor includes:
 a ferromagnetic layer including a three-layer structure; and   an antiferromagnetic layer.    
     
     
       72. A ferromagnetic thin-film based magnetic field sensor comprising:
 a first plurality of magnetoresistive sensors coupled to sense a first magnetic field in a direction orthogonal to a plane of the first plurality of magnetoresistive sensors, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors includes a sensing element;   one or more flux guides, wherein each flux guide of the one or more flux guides includes a soft ferromagnetic material, wherein the soft ferromagnetic material is a high permeability magnetic material, wherein at least one flux guide of the one or more flux guides is associated with the sensing element of at least one magnetoresistive sensor of the first plurality of magnetoresistive sensors, and wherein (i) the at least one flux guide is in a plane that is above or below the associated sensing element in the direction and parallel to the associated sensing element, (ii) the at least one flux guide is disposed non-parallel to a first side of the at least one magnetoresistive sensor, and (iii) the at least one flux guide includes an end that is proximate to a first edge of the associated sensing element and on a first side of the associated sensing element; and   a second plurality of magnetoresistive sensors configured to be electrically connected together to sense a second magnetic field orthogonal to the first magnetic field;   wherein each flux guide of the one or more flux guides includes (i) a first vertical segment, (ii) a second vertical segment, and (iii) a horizontal segment connecting the first and second vertical segments, and wherein a free end of the first vertical segment is flared away from a free end of the second vertical segment, each flux guide having the flared-away free ends at least partially enclosing a cladded line between the two vertical segments, and wherein the first vertical segment, the second vertical segment, and the horizontal segment define an opening, the opening having a width defined by a distance between inner walls of the first and second vertical segments, wherein the width of the opening between the inner walls at the flare-away free ends is larger than the width of the opening between the inner walls at connected ends of the first and second vertical segments, the first and second vertical segments being connected to the horizontal segment at the connected ends.    
     
     
       73. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the high permeability magnetic material is nickel iron (NiFe).  
     
     
       74. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors is connected to form a circuit, and wherein the circuit includes input terminals configured to receive an electrical power and output terminals connected to a voltage meter.  
     
     
       75. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein first plurality of magnetoresistive sensors is connected into a bridge circuit having input terminals and output terminals.  
     
     
       76. The ferromagnetic thin-film based magnetic field sensor of claim 75, wherein the input terminals are configured to receive electrical power and the output terminals are connected to a voltmeter to measure an output signal.  
     
     
       77. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the sensing element of each magnetoresistive sensor is disposed adjacent to a reference layer, and wherein an intermediate layer is disposed between the sensing element and the reference layer.  
     
     
       78. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the sensing element of each magnetoresistive sensor is disposed adjacent to a reference layer, and wherein an insulating dielectric layer is disposed between the sensing element and the reference layer.  
     
     
       79. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor of the first plurality of magnetoresistive sensors is a magnetic tunnel junction sensor.  
     
     
       80. The ferromagnetic thin-film based magnetic field sensor of claim 72, further comprising:
 a third plurality of magnetoresistive sensors electrically connected together to sense a third magnetic field orthogonal to the first and second magnetic fields.    
     
     
       81. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors is connected together to generate a sensor signal, and wherein the first magnetic field in the direction is determined based on the sensor signal.  
     
     
       82. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor,
 wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, and a fourth flux guide, and   wherein the first flux guide is associated with the first magnetoresistive sensor, the second flux guide is associated with the second magnetoresistive sensor, the third flux guide is associated with the third magnetoresistive sensor, and the fourth flux guide is associated with the fourth magnetoresistive sensor.    
     
     
       83. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor,
 wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, and a fourth flux guide, and   wherein the first flux guide is above the first magnetoresistive sensor, the second flux guide is below the second magnetoresistive sensor, the third flux guide is above the third magnetoresistive sensor, and the fourth flux guide is below the fourth magnetoresistive sensor.    
     
     
       84. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor, a second magnetoresistive sensor, a third magnetoresistive sensor, and a fourth magnetoresistive sensor, each of the first, second, third, and fourth magnetoresistive sensors including a first side and a second side opposite to the first side,
 wherein the one or more flux guides comprises a first flux guide, a second flux guide, a third flux guide, a fourth flux guide, a fifth flux guide, a sixth flux guide, a seventh flux guide, and an eighth flux guide, and   wherein the first flux guide is below the first side of first magnetoresistive sensor, the second flux guide is above the second side of the first magnetoresistive sensor, the third flux guide is above the first side of the second magnetoresistive sensor, the fourth flux guide is below the second side of the second magnetoresistive sensor, the fifth flux guide is below the first side of the third magnetoresistive sensor, the sixth flux guide is above the second side of the third magnetoresistive sensor, the seventh flux guide is above the first side of the fourth magnetoresistive sensor, and the eighth flux guide is below the second side of the fourth magnetoresistive sensor.    
     
     
       85. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected for differential measurement.  
     
     
       86. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, subtract resistances of the first and second magnetoresistive sensors.  
     
     
       87. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, produce a response when sensing the second magnetic field.  
     
     
       88. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, eliminate a response generated when sensing the second magnetic field.  
     
     
       89. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the first plurality of magnetoresistive sensors comprises a first magnetoresistive sensor and a second magnetoresistive sensor, and wherein the first and second magnetoresistive sensors are connected to, in operation, double a magnetic field measurement when sensing the first magnetic field.  
     
     
       90. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer and an intermediate layer disposed between the sensing element and the reference layer.  
     
     
       91. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer includes a plurality of layers having a combined thickness in a range of 10 to 1000 Å.  
     
     
       92. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer includes a plurality of layers having a combined thickness in a range of 250 to 350 Å.  
     
     
       93. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer comprises:
 a ferromagnetic layer; and   an antiferromagnetic layer.    
     
     
       94. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer comprises:
 a ferromagnetic layer having a thickness in a range of 20 to 80 Å; and   an antiferromagnetic layer having a thickness of approximately 200 Å.    
     
     
       95. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer comprises:
 a ferromagnetic layer; and   an antiferromagnetic layer including iridium-manganese (IrMn) alloy or platinum-manganese (PtMn) alloy.    
     
     
       96. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein each magnetoresistive sensor further includes a reference layer, and wherein the reference layer comprises:
 a ferromagnetic layer including a three-layer structure; and   an antiferromagnetic layer.    
     
     
       97. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the sensing element includes a thickness in a range of 10 to 5000 Å.  
     
     
       98. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the sensing element includes a thickness in a range of 10 to 60 Å.  
     
     
       99. The ferromagnetic thin-film based magnetic field sensor of claim 72, wherein the ferromagnetic thin-film based magnetic field sensor is configured to generate a sensor signal, and wherein the first magnetic field is determined based on the sensor signal.