Magnetic properties of crystalline and amorphous Fe-Ni alloy films deposited by sputtering

Abstract

In order to investigate the peculiar magnetovolume coupling in the Fe-Ni Invar alloy, the relation between the magnetization and the interatomic distance is studied by the Mössbauer effect and x-ray diffraction analysis for the FexNi1−x alloy foils which are obtained by dc sputter deposition. The interatomic distance of the sputter-deposited Fe-Ni alloy foils depends on the sputtering voltage; the sputter deposition at low voltage produces an extended lattice, and further lowering of the sputtering voltage gives rise to an amorphous state. The hyperfine field of the extended lattice in the Invar composition which is produced by sputtering at 2 kV is about 10% larger than that of the bulk alloy and furthermore the extended lattice does not retain the Invar characteristics such as low thermal expansion. The hyperfine field of the amorphous state produced by the lower-voltage sputtering at 1.5 kV doesn’t show the abrupt decrease around the Invar composition range in contrast to that of the crystalline Fe-Ni alloys, where a sharp drop of the hyperfine field is well known. The lack of the Invar characteristics in the sputter-deposited Fe-Ni alloys is discussed on the basis of the change of the 3d band configuration which leads to the disappearance of the weak itinerant ferromagnetic state.