Method to make superior soft (low Hk), high moment magnetic film and its application in writer heads

Abstract

A process sequence for forming a soft magnetic layer having Hce and Hch of ≦2 Oe, Hk≦5 Oe, and Bs of ≧24 kG is disclosed. A CoFe or CoFe alloy is electroplated in a 10 O C to 25 O C. bath (pH 2 to 3) containing Co +2 and Fe +2 ions in addition to boric acid and one or more aryl sulfinate salts to promote magnetic softness in the deposited layer. Peak current density is 30 to 60 mA/cm 2 . A two step magnetic anneal process is performed to further improve softness. An easy axis anneal is followed by a hard axis anneal or vice versa. In an embodiment where the magnetic layer is a pole layer in a write head, the temperature is maintained in a 180 O C to 250 O C range and the applied magnetic field is kept a 300 Oe or below to prevent degradation of an adjacent read head.

1 . A method for forming a soft magnetic layer having a high saturation magnetization (Bs), comprising:
 (a) electroplating a soft magnetic layer on a substrate, said soft magnetic layer has a first axis magnetization direction and a second axis magnetization direction wherein the first axis intersects the second axis;   (b) performing a first anneal step wherein a first magnetic field is applied along the first axis; and   (c) performing a second anneal step wherein a second magnetic field is applied along the second axis.   
     
     
         2 . The method of  claim 1  wherein the first axis is the easy axis and the second axis is the hard axis. 
     
     
         3 . The method of  claim 1  wherein the first axis is the hard axis and the second axis is the easy axis. 
     
     
         4 . The method of  claim 1  wherein said electroplating comprises an electroplating bath comprised of Fe +2  ions, Co +2  ions, boric acid, one or more aryl sulfinate salts, and said electroplating bath is maintained at a pH between about 2 and 3, and in a temperature range from about 10 O  C to 25 O  C. 
     
     
         5 . The method of  claim 4  wherein said electroplating further comprises applying a peak current density between about 30 and 60 mA/cm 2  during one or more cycles based on an “ON” time of about 10 to 50 ms and an “OFF” time of about 20 to 200 ms. 
     
     
         6 . The method of  claim 4  wherein said electroplating bath is comprised of ferrous sulfate at a concentration of about 50 to 140 g/L, cobalt sulfate at a concentration of about 20 to 70 g/L, boric acid at a concentration of about 20 to 40 g/L, sodium benzenesulfinate at a concentration of about 0.05 to 0.3 g/L, and is further comprised of nickel sulfate at a concentration of 0 to about 70 g/L, one or more electrolytes at a concentration of about 0.5 to 50 g/L, a surfactant at a concentration of 0 to about 0.15 g/L, and a stress reducing agent with a concentration of 0 to about 2 g/L. 
     
     
         7 . The method of  claim 1  wherein said first anneal step and said second anneal step are comprised of a temperature between about 180 O  C and 250 O  C for a period of about 20 to 300 minutes. 
     
     
         8 . The method of  claim 1  wherein the first magnetic field is between about 200 Oe and 300 Oe and the second magnetic field is between about 200 Oe and 300 Oe. 
     
     
         9 . The method of  claim 1  wherein said soft magnetic layer is CoFe, a CoFe alloy, NiFe, or a NiFe alloy. 
     
     
         10 . The method of  claim 1  wherein the soft magnetic layer has an easy axis coercivity (Hce) and a hard axis coercivity of about 2 Oe or less, an anisotropy field (Hk) of about 5 Oe or less, and a Bs of ≧24 kG. 
     
     
         11 . The method of  claim 1  wherein the soft magnetic layer is a pole layer in a write head. 
     
     
         12 . A method for softening a magnetic layer on a substrate, said magnetic layer has a first axis magnetization direction and a second axis magnetization direction; comprising:
 (a) performing a first anneal step wherein a first magnetic field is applied along the first axis; and   (b) performing a second anneal step wherein a second magnetic field is applied along the second axis.   
     
     
         13 . The method of  claim 12  wherein the soft magnetic layer is comprised of CoFe, a CoFe alloy, NiFe, or a NiFe alloy. 
     
     
         14 . The method of  claim 12  wherein the first axis is the easy axis and the second axis is the hard axis. 
     
     
         15 . The method of  claim 12  wherein first axis is the hard axis and the second axis is the easy axis. 
     
     
         16 . The method of  claim 12  wherein said first anneal step and said second anneal step are comprised of a temperature between about 180 O  C and 250 O  C for a period of about 20 to 300 minutes. 
     
     
         17 . The method of  claim 12  wherein the first magnetic field is between about 200 Oe and 300 Oe and the second magnetic field is between about 200 Oe and 300 Oe. 
     
     
         18 . The method of  claim 12  wherein the soft magnetic layer is a pole layer in a write head. 
     
     
         19 . The method of  claim 16  wherein the substrate is cooled between the first anneal step and the second anneal step. 
     
     
         20 . The method of  claim 12  wherein easy axis coercivity (Hce), hard axis coercivity (Hch), and anisotropy field (Hk) are all substantially reduced compared to the magnetic layer properties prior to the double annealing process.