Acceleration of ordering transformation of a new Fe2(Mn,Cr)Si Heusler-alloy film by very high frequency plasma irradiation process during radio frequency sputter deposition

A new Heusler alloy, Fe2(Mn,Cr)Si, that is likely to have high spin polarization (P) and high damping constant (α) was proposed to obtain high magneto-resistance ratio and low spin torque noise in a magnetic read head with a current-perpendicular-to-plane (CPP) giant magneto-resistance (GMR) multilayer. A very high frequency (VHF) plasma irradiation process during radio frequency (RF) sputter deposition was investigated to form the highly ordered structure of the Heusler alloy film with low thermal treatment temperature. The main results are as follows: (1) P and magnetic moment of Fe2(Mn0.5Cr0.5)Si with an L21 structure were estimated at 0.99 and 2.49 μB/f.u., respectively, and α was also estimated to be larger compared with the case of Co2MnSi, according to density of states (DOS) calculations. (2) The ordering (at least B2 structure) temperature of Fe2(Mn0.6Cr0.4)Si film decreased from 500 to 300 deg. C by using the VHF plasma irradiation process with optimized condition. (3) The surface roughness of Fe2(Mn0.6Cr0.4)Si film also reduced from 1.7 to 0.5 nm by using the VHF plasma irradiation process. It is found that the Fe2(Mn,Cr)Si Heusler alloy and the VHF plasma irradiation process with optimized condition seems to be applicable for fabrication of high-performance magnetic read head with CPP-GMR device.