Thin film magnet, cylindrical ferromagnetic thin film and production method thereof

Abstract

A thin film magnet and a cylindrical ferromagnetic thin film having a high maximum energy product (greater than 120 kJ/m3) and thus suitable for use in miniature high performance devices are provided. The thin film magnet is produced by means of physical vapor deposition. The thin film magnet is an (Nd1-xRx)yM1-y-zBz alloy having a ferromagnetic compound of the Nd2Fe14B type as its main phase, wherein R is Tb, Ho, and Dy and M is Fe metal or an Fe-based alloy including at least one of Co and Ni, 0.04</=x</=0.10,0.11</=y</=0.15, and 0.08</=z</=0.15. A perpendicular magnetization film having such a composition is deposited on the side wall of a substrate in the columnar (or cylindrical) form thereby obtaining a cylindrical ferromagnetic thin film having radial anisotropy.

What is claimed is: 
     
       1. An article comprising a structure having a coating thereon comprising a thin film magnet produced by means of physical vapor deposition, said thin film magnet comprising an (Nd 1-x  R x ) y  M 1-y-z  B z  alloy having a ferromagnetic compound .[.comprising.]. .Iadd.with an .Iaddend.Nd 2  Fe 14  B .Iadd.structure type .Iaddend.as its main phase, wherein R is at least one element selected from the group consisting of Tb, Ho, and Dy and M is Fe metal or an Fe-based alloy consisting of at least one element selected from the group consisting of Co and Ni, 0.04≦x≦0.10, 0.11≦y≦0.15, and 0.08≦z≦0.15. 
     
     
       2. A method for producing an article comprising a thin film magnet by forming a thin film magnet on a substrate placed in a vacuum chamber, said thin film magnet comprising an (Nd 1-x  R x ) y  M 1-y-z  B z  alloy having a ferromagnetic compound .[.comprising.]. .Iadd.with an .Iaddend.Nd 2  Fe 14  B .Iadd.structure type .Iaddend.as its main phase, wherein R is at least one element selected from the group consisting of Tb, Ho, and Dy and M is Fe metal or an Fe-based alloy including at least one element selected from the group consisting of Co and Ni, 0.04≦x≦0.10, 0.11≦y≦0.15, and 0.08≦z≦0.15. 
     
     
       3. A method according to claim 2, wherein said substrate is heated to a temperature in the range of from about 530° to about 570° C. during said formation step. 
     
     
       4. A method according to claim 2, wherein the deposition rate of said magnetic thin film during said formation step is in the range of from about 0.1 to about 4 μm/hr. 
     
     
       5. A method according to claim 2, wherein said formation step is carried out at a gas pressure in the range of from about 0.05 to about 4 Pa. 
     
     
       6. An article comprising: a cylindrical or columnar substrate, and a perpendicular magnetization film deposited on the side wall of said substrate, said ferromagnetic thin film having radial anisotropic magnetic properties. 
     
     
       7. An article according to claim 6, wherein said perpendicular magnetization film is a thin film magnet comprising an (Nd 1-x  R x ) y  M 1-y-z  B alloy having a ferromagnetic compound .[.comprising.]. .Iadd.with an .Iaddend.Nd 2  Fe 14  B .Iadd.structure type .Iaddend.as its main phase, wherein R is at least one element selected from the group consisting of Tb, Ho, and Dy and M is Fe metal or an Fe-based alloy including at least one element selected from the group consisting of Co and Ni, 0.04≦x≦0.10, 0.11≦y≦0.15, and 0.08≦z≦0.15. 
     
     
       8. An article according to claim 6, wherein a buffer layer is formed between said substrate and said perpendicular magnetization film. 
     
     
       9. A method for producing a ferromagnetic thin film in cylindrical form on a substrate by means of physical vapor deposition, said method including the steps of heating a cylindrical or columnar substrate, and depositing a perpendicular magnetization film on the side wall of said substrate. 
     
     
       10. A method for producing a ferromagnetic thin film in cylindrical form according to claim 9, wherein said perpendicular magnetization film is a thin film magnet comprising an (Nd 1-x  R x )hd yM 1-y-z  B z  alloy having a ferromagnetic compound .[.comprising.]. .Iadd.with an .Iaddend.Nd 2  Fe 14  B .Iadd.structure type .Iaddend.as its main phase, wherein R is at least one element selected from the group consisting of Tb, Ho, and Dy and M is Fe metal or an Fe-based alloy including at least one element selected from the group consisting of Co and Ni, 0.04≦x≦0.10, 0.11≦y≦0.15, and 0.08≦z≦0.15. 
     
     
       11. A method for producing a ferromagnetic thin film in cylindrical form according to claim 9, further including the step of forming a buffer layer between said substrate and said perpendicular magnetization film. 
     
     
       12. A method for producing a ferromagnetic thin film in cylindrical form according to claim 9, wherein said substrate is heated to a temperature in the range of from about 530° to about 570° C. during said heating step. 
     
     
       13. A method for producing a ferromagnetic thin film in cylindrical form according to claim 9, wherein the deposition rate of said magnetic thin film during said depositing step is in the range of from about 0.1 to about 4 μm/hr. 
     
     
       14. A method for producing a ferromagnetic thin film in cylindrical form according to claim 9, wherein said depositing step is carried out at a gas pressure in the range of from about 0.05 to about 4 Pa. 
     
     
       15. A method for producing a ferromagnetic thin film in cylindrical form according to claim 9 comprising producing a ferromagnetic thin film having radial anisotropic magnetic properties.