Recently Co_1-xFe_xS₂ has been proposed as a tunable source of highly spin-polarized electrons, based on the fact that the Fermi level may be fine-tuned by solid solution alloying with the isostructural diamagnetic semiconductor FeS₂ having the pyrite structure. Anisotropic magnetoresistance measurements have been used as a probe of the sign of carrier polarization.

In this study we report on the preparation, magnetic and magnetotransport properties, of (Co,Fe)S₂ thin films. The films have been prepared by thermal-sulfuration of Co_1-xFe_x films in a sulfur atmosphere at 500⁰C, at a sulfur pressure of 1 atm for 12 hrs. Co₅₀Fe₅₀ films prepared by Pulsed Laser Deposition (PLD) as well as Magnetron Sputtered Co₃₀Fe₇₀ films have been used. Proper adjustment of heat treatment conditions is crucial in order to achieve the correct sulfur stoichoiometry throughout the film. Thicker films show a cusp in the magnetization versus temperature curves around 100K which indicates an inhomogeneous nature.

The resistivity decreases monotonously as a function of temperature and shows a plateau at the Curie temperature. In the MR curves a small (2%) low field extrinsic contribution is observed at 5K which decreases rapidly with temperature and disappears well below the Curie temperature of 135K. This extrinsic MR is increased (4%) for thinner films. Above the Curie temperature a quadratic MR term dominates. The coercivity decreases linearly with temperature. The Hall effect measurements show a substantial Anomalous Hall Effect (AHE) contribution that is superimposed at the ordinary Hall effect and disappears at the T_C.

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