Martensitic phase mechanism of ternary FeCrMn thin films influenced by the substrate rotation speeds: structural and magnetic properties

Abstract

In order to investigate the martensitic phase mechanism of the ternary FeCrMn thin films sputtered under the effect of substrate rotation speeds, the structural and related magnetic properties were studied. A range of thin films were deposited at varying rotational speeds of 0, 15, 30, and 45 rpm on flexible amorphous polymer substrates through the use of DC magnetron sputtering. The films were 50 nm thick and were produced at 0.09 nm s-1. The crystal structures showed that all films have a mixture of the body-centred tetragonal (bct) and tetragonal structure. The peak intensity of bct (110) martensitic alpha'phase increased with the increase of the rotation speeds whereas the tetragonal (430) and (333) peaks stayed almost stable. And, the morphologic surface analysis displayed that the smooth surface turned into a rough surface with the increase of the rotation speeds. After the measurements of hysteresis loops, the films obtained by sputtering of austenitic target have ferromagnetic character with increasing saturation magnetization, MS and coercivity, HC as the substrate rotation speeds increase. With increasing rotation speeds, the increase of the MS from 148 to 242 emu cm-3 and the rise of the HC of the films from 21 to 185 Oe might be explained by the increase of the grain sizes with the increase of % martensitic alpha'phase caused by increasing rotation speeds. The ternary FeCrMn thin films exhibit increasing % martensitic alpha'phase and corresponding ferromagnetic properties with increasing substrate rotation speeds. It is concluded that the nanostructured films of FeCrMn have different properties from those of their bulk counterparts under the influence of substrate rotation speeds. Therefore, the martensitic mechanism of the films can easily be controlled by changing rotation speed for potentially flexible new device applications such as spintronics, magnetic hetero-structures, magnetic separators, etc.