Room temperature ferromagnetism and anomalous Hall effect in Si$_{1-x}$Mn$_x$ ($x\approx 0.35$) alloys

B. A. Aronzon, V. V. Rylkov, S. N. Nikolaev, V. V. Tugushev, S. Caprara, V. V. Podolskii, V. P. Lesnikov, A. Lashkul, R. Laiho, R. R. Gareev, N. S. Perov, A. S. Semisalova

Published 2010-12-06Version 1

A detailed study of the magnetic and transport properties of Si$_{1-x}$Mn$_x$ ($x\approx 0.35$) films is presented. We observe the anomalous Hall effect (AHE) in these films up to room temperature. The results of the magnetic measurements and the AHE data are consistent and demonstrate the existence of long-range ferromagnetic (FM) order in the systems under study. A correlation of the AHE and the magnetic properties of Si$_{1-x}$Mn$_x$ ($x\approx 0.35$) films with their conductivity and substrate type is shown. A theoretical model based on the idea of a two-phase magnetic material, in which molecular clusters with localized magnetic moments are embedded in the matrix of a weak itinerant ferromagnet, is discussed. The long-range ferromagnetic order at high temperatures is mainly due to the Stoner enhancement of the exchange coupling between clusters through thermal spin fluctuations (paramagnons) in the matrix. Theoretical predictions and experimental data are in good qualitative agreement.