Atomic diffusion and microstructure of SmCo5 multilayers with high coercivity

Sm-Co multilayer films are deposited by plasma sputtering with a Cr underlayer and a Cu buffer layer, followed by annealing at different temperatures. The as-deposited films show low hard magnetic properties due to the existing amorphous Sm-Co phase. After annealing, for the films without Cu buffer layer, there is only Sm2Co17 phase in the films even at high annealing temperature and the coercivity is less than 12kOe. When inserting a Cu buffer layer, the well-crystalline SmCo5 single phase is obtained at relatively lower annealing temperature (500 degrees C and 550 degrees C) and extremely high in-plane coercivity (38kOe) is achieved. An analysis of Transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) reveals that Cu atoms started to diffuse during the annealing process induced by thermal dynamics, concentration gradient and microstructure variations, and eventually uniformly distribute in SmCo layer and form Sm(Co,Cu)(5) phase. The exchange interaction energy calculation indicates that small fraction of Cu atoms preferentially substitute the Co(2c) site in SmCo5 lattice, which reduces the exchange coupling effects of Sm-Co and gives rise to the coercivity. The results provide a guidance to fabrication of single-phase Sm(Co,Cu)(5) multilayer films with superior performance that have applications in advanced electromagnetic and electronic devices. (c) 2017 Elsevier B.V. All rights reserved.