Structure and properties of ion-plasma deposited films of CoCrFeMiMn high-entropy alloy

Abstract

High-entropy Co19Cr18Fe22Mn21Ni20 thin films were obtained by the modernized method of three-electrode ion-plasma sputtering of mosaic targets consisting of pure metals. The structure, electrical resistance, and magnetic properties of films were investigated. Single diffuse halo was seen on the XRD patterns of the as-deposited films, which confirms their amorphous structure. Some of the thin films, which were annealed at 900 K in a vacuum, were identified to be oxidized by a small amount of oxygen in the work chamber. After the heat treatment, the Co19Cr18Fe22Mn21Ni20 films were transformed from an amorphous state into a crystallized FCC solid solution with the lattice parameter a=0.3613 nm. Also, the cubic B2 phase of FeCo with a lattice parameter of 0.2857 nm was formed in the annealed films. As a result of oxidation processes, a dispersed phase of manganese oxide also arose after annealing. The temperature dependencies of electrical resistivity of films were measured by the four-point technique upon continuously heating in the high vacuum. Both as-deposited and annealed films clearly revealed a typical ferromagnetic behavior. The as-deposited high-entropy film exhibited the soft magnetic properties while the annealed films could be attributed to hard magnetic materials.