Effect of Low Temperature Annealing on High Field Magnetoresistance and Hall effect in (Ga,Mn)As Dilute Magnetic Semicon
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Effect of Low Temperature Annealing on High Field Magnetoresistance and Hall effect in (Ga,Mn)As Dilute Magnetic Semiconductors K. Ghosh1, Mohammad Arif1, T. Kehl1, R. J. Patel1, S. R. Mishra2, and J. G. Broerman1 1 Department of Physics, Astronomy & Materials Science, Southwest Missouri State University, Springfield, MO 65804, U.S.A. 2 Department of Physics, the University of Memphis, Memphis, TN 38152, U.S.A. ABSTRACT In this paper we report the effect of low temperature annealing on the high field magnetotransport properties of epitaxial thin films of (Ga,Mn)As Dilute Magnetic Semiconductor (DMS) with low concentration (1.5 %) of Mn doping, which results in a ferromagnetic insulator. Annealing at an optimal temperature enhances the conductivity, carrier concentration, and ferromagnetic transition temperature. The field dependence of magnetoresistance is different below and above the ferromagnetic transition temperature. An attempt is made to analyze the data using a theoretical model proposed by Kaminski and Das Sarma [1]. INTRODUCTION The subject of spintronics has acquired considerable significance in recent years due to potential device applications such as electro-optic switches, ultra-sensitive magnetic field sensors, spin-polarized solar batteries, and quantum-based logic and memory for high speed computation[2,3]. The ultimate success of the field of spintronics depends on materials with large spin polarization thus significant research has been conducted on DMS materials, which have 100% spin polarization. Theoretical calculations predict that doping III-V and II-VI semiconductors with 3-5% manganese (Mn) leads to ferromagnetic ordering [4]. Several experiments with Mn doped GaP, Cr doped GaN, and Mn doped GaAs [5,6] have confirmed on such ferromagnetic ordering. It has also been found that doping of magnetic ions such as Fe, Co or Mn in metal oxides (ZnO, SnO2 and TiO2), produces DMS [7,8,9]. Some of them show ferromagnetic ordering close to or above room temperature. For example, Co doped TiO2 undergoes ferromagnetic ordering with a significantly high Curie temperature (TC) of ~ 1180 K [8]. Although ferromagnetism has been observed in several classes of dilute magnetic semiconductors, the canonical DMS (Ga,Mn)As is of particular interest. (Ga,Mn)As provides a model system in which, carrier-mediated ferromagnetism persists above 100 K [10,11]. During the last few years much attention has been given to (Ga,Mn)As to understand the origin of ferromagnetism in DMS materials [12,13,14]. Most of the current experimental work on this system has been directed towards enhancing TC and concentrating on the metallic DMS ferromagnetic regime [11,15]. However, the insulating DMS ferromagnetic regime has not yet been extensively studied experimentally compared to the metallic DMS regime with optimal TC values. This regime is as important and as interesting as the metallic regime in terms of the development of understanding the physics of DMS. Recently, Kamaniski and Das Sarma developed a theory for insulating
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