High-temperature ferromagnetism of Si$_{1-x}$Mn$_x$ films fabricated by laser deposition using the droplet velocity separation technique

The transport and magnetic properties of Si$_{1-x}$Mn$_x$ films of thickness 55–70 nm with various Mn content ($x$ = 0.44–0.6) are studied in the temperature range of 5–400 K and in magnetic fields up to 2 T. The films are grown by pulsed laser deposition on Al$_2$O$_3$ (0001) substrates at a temperature of 340$^\circ$C using velocity separation of deposited particles. The films exhibit metal conductivity and the resistivity $\rho$ = (2–8) $\times$ 10$^{-4}$, typical of highly degenerate semiconductors. It is found that the anomalous component of the Hall effect dominates over the normal component at $T$ = 300 K for the Si$_{1-x}$Mn$_x$ alloy with $x\approx$ 0.5, and that the Curie temperature significantly exceeds room temperature and is estimated as $\sim$500 K from magnetization measurements (for MnSi silicide the Curie temperature is $T_\mathrm{C}$ = 30 K). It is shown that the anomalous component of the Hall conductivity at low temperatures is controlled by “side-jump” and (or) “intrinsic” mechanisms independent on the carrier scattering time. The results are explained by features of the formation of defects with localized magnetic moments in the case of Si$_{1-x}$Mn$_x$ films with $x\approx$ 0.5 and by the significant role of matrix spin fluctuations in the exchange between these defects.