Low-coercivity amorphous magnetic alloy films

Abstract

It is well known that rapidly quenched bulk samples of amorphous transition-metal-metalloid alloys can be made with high permeability and low coercivity; however, little is known of the magnetic properties of these alloys when prepared by thin-film-deposition techniques. Sputter-deposited films of iron-carbon, iron-silicon-boron, iron-chromium-phosphorus-carbon, cobalt-iron-boron, and cobalt-iron-chromium-phosphorus-boron have been prepared, and it is shown that these films can be made with low coercivity and high saturation magnetization by proper choice of deposition conditions. The magnetic properties of iron-carbon films were found to depend on the sputtering conditions, in particular on the argon-gas pressure. At an argon-gas pressure of 15 μm, films with 70 at.% iron and 30 at.% carbon were obtained with a 4πMs of 12 000 G and coercivities in the range 0.1-0.9 Oe. Films made with higher and lower argon-gas pressure had significantly higher coercivity. Other alloys were prepared to explore corrosion and magnetostriction behavior. Films which were extremely corrosion resistant were deposited from a target of 74 at.% iron, 6 at.% chromium, 13 at.% phosphorus, and 7 at.% carbon. Amorphous films of iron-silicon-boron made in an attempt to find small and/or negative λs possessed large positive λs. Films of CoFe-B were found to have λs?0 and generally excellent magnetic properties. Adding Cr and P to the CoFe-B target did not significantly improve the corrosion resistance of the films.