Turn on/off the high-temperature ferromagnetism in Si1-xMnx thin films through Mn-ion implantation

Silicon based alloys with Mn-ions are a potential candidate for the spintronics applications, as they exhibit complex electric and magnetic phenomena which can be effectively utilized as the integrated-circuit elements in the contemporary microelectronic technology. Though, The Si1-xMnx alloys shows high-temperature ferromagnetism at low Mn concentration x ~ 0.05 – 0.1, but the small solubility of Mn-ions in Si leads to the formation of MnSi1.7 nanoparticles,1 which drives the system in an inhomogeneous phase and makes it irrelevant for the technological applications. However, a high Mn concentration in the Si1-xMnx alloys screens the precipitation of different inhomogeneous magnetic phases with high Curie temperature (TC).2 In this context, a set of thin films of Si1-xMnx (x = 0.44 – 0.57) alloy were prepared by the pulsed laser deposition technique on Al2O3 (0001) substrate. We have found room temperature ferromagnetism and a large magnetic moment for the Si0.43Mn0.57 film as compared to the rest of samples. But, surprisingly, the TC (as well as the moment) of Si0.43Mn0.57 film drastically decreases from 300 K to ~ 40 K as the Mn-ion concentration was increased in the film through the ion implantation process. In contrast, the stoichiometric film Si0.5Mn0.5 exhibits a huge increase in the magnetic moment by one-order in magnitude after ~ 2% Mn-ion implantation. The TC of the stoichiometric film also increases from 50 K to 300 K with the increase in the Mn-ion concentration.