Magnetic properties of ion beam sputtered Co-Zr and Co-Zr-Re amorphous films

In this paper, the optimum deposition conditions of amorphous Co-Zr films fabricated by ion beam sputtering and their magnetic properties are investigated. The amorphous state is achieved at a low Zr content ( near 5 - 10 at% ) and is dependent on the substrate temperature. Co-Zr alloy films with a Zr content of 4.5 at% become amorphous on a -130 °C substrate, whereas a Zr content of more than 6 at% is necessary to obtain amorphous films on a 40 °C substrate. The resistivity of the films increases monotonically with Zr content or as the substrate temperature decreases from +300 °C to -130 °C. It is shown that the addition of a small amount of Re to the films decreases magnetostriction, although it lowers saturation magnetization slightly. A magnetostriction value of less than 10^-7is obtained when 2 to 3 at%Re is added to the Co-Zr films with a 6 to 8 at%Zr. Ion beam sputtered Co-6 at %Zr-2at% Re in 1 to 3 μm thick amorphous films exhibits the following excellent properties: a saturation magnetization of more than 13 kG, a permeability at 10 MHz of more than 5000, and a Vickers hardness of over 700.