Structural and Magneto-transport Properties of Cr-doped In 2 O 3 Diluted Magnetic Semiconductors
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Structural and magneto-transport properties of Cr-doped In2O3 diluted magnetic semiconductors N.B. Ukah1, R.K. Gupta1, K. Ghosh1, P.K. Kahol1, R. Giedd2 1 Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, Missouri-65897, USA 2 Roy Blunt Jordan Valley Innovation Center, Missouri State University, Springfield, Missouri65806, USA ABSTRACT We report the experimental study of the structural and magnetotransport properties of chromium-doped indium oxide (In2O3:Cr) thin films using x-ray diffractometer, and by measuring the resistivity and Hall effect as a function of temperature in various magnetic fields. The In2O3:Cr diluted magnetic semiconductor thin films were grown under different partial oxygen pressures (Po2) on sapphire substrates using pulsed laser deposition (PLD) technique. Observed expansions in lattice parameter and crystal size in these films with increase in oxygen growth pressure are traceable to the reduction in oxygen vacancies. A redshift of the absorption edges of the samples with increase in oxygen growth pressure is attributed to the significant improvement in crystallinity. The exchange interaction between the electron spins in the conduction band and the spins of the Cr 3d electrons was evident in the anomalous Hall effect (AHE), which persisted up to 300 K. An analysis of the dc electrical transport in the films was carried out using hopping conduction and ionized impurity scattering models. INTRODUCTION Earlier than the last two and a half decades or so, semiconductor research has largely remained within the confines of conventional semiconductor electronics, which is based only on the manipulation of the charge of the electron. But lately, enormous research efforts have been channeled at electron spin manipulation arising from its relevance in the realization of especially high curie temperature (Tc) ferromagnetic semiconductors critical for spin electronics [1, 2]. Diluted magnetic semiconductor (DMS) materials, which have turned out to be potential candidates for the realization of spintronic devices are obtained by doping transition metals into semiconductor host lattices such as Cr in AlN or GaN [2]. Indium oxide is a transparent, n-type material with inherent oxygen vacancies whose conductivity can be effectively varied by varying the oxygen vacancies or by Sn doping [3]. In comparison with most transition metals, Cr has large magnetic moment in the ionic state. Also the observation of ferromagnetism due to Cr clustering is unlikely since small amounts of Cr clusters result in superparamagnetism, and bulk Cr is antiferromagnetic [4]. Therefore, it is believed that In2O3 and Cr would be suitable materials for spintronic semiconductor devices. Various studies of magnetotransport properties of ferromagnetic semiconductors namely (Ga,Mn)N [5] and (Ga,Mn)As [6] have been reported. J. Philip et al. [7] have reported high temperature ferromagnetism (FM) in In2O3:Cr thin films grown by co-evaporation technique, and proposed that carrier-m
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