Carrier mediated Ferromagnetism in Cr: In$_{2}$O$_{3}$

While a number of Dilute Magnetic Semiconducting Oxides (DMSO), when doped with transition metals, exhibit ferromagnetism well above room temperature, most of them are insulating and hence the relationship between the charge carriers and ferromagnetism remains unclear. Here, we investigate a high Curie temperature DMSO, Cr:In$_{2}$O$_{3}$, which is made conductive down to low temperatures. Films of various thicknesses ranging from 200 nm to 1100 nm were grown on sapphire substrate by rf sputtering. Upon vacuum annealing, the samples became both magnetic (with the saturation magnetization $\sim $0.07$\mu $B/Cr) and highly conductive, in contrast to as-prepared samples which were both non-magnetic and insulating. Point Contact Andreev Reflection (PCAR) spectroscopy with the superconducting Sn tip demonstrated significant (50 {\%} $\pm $ 5{\%}) transport spin polarization, strongly suggesting that ferromagnetism in Cr:In$_{2}$O$_{3}$ is carrier-mediated. We will discuss the implications of these results on our understanding of the nature of ferromagnetic interactions in DMSOs, as well Cr: In$_{2}$O$_{3}$ potential applications as a spin injector.