Antiferro-ferromagnetic transition and microstructural properties in a sputter deposited FeRh thin film system

Magnetic and microstructural properties are studied in sputter deposited Fe100−xRhx alloy (28.0<x<57.0) thin films. As-deposited films show a preferred (111) oriented fcc phase at x≳35.0. Annealing at 600 °C results in the CsCl type structure which exhibits a preferred (110) orientation with the same lattice constant as that of bulk. However, an incomplete antiferro-ferromagnetic transition with large thermal hysteresis is observed in a wider composition range (x≳45.4) than bulk. Furthermore, magnetization at room temperature decreases continuously from x=35.0 to x=57.0 in contrast to the sharp drop at x=50 in bulk. By using scanning and transmission electron microscopy and Mössbauer spectroscopy, it is found that the retained fcc phase and compositional fluctuation strongly affect the magnetic transition. The retained fcc phase surprisingly reduces the grain growth of the CsCl type ordered phase from 4000 to 300 Å as the Rh content increases from 45.4% to 54.0%.