Room Temperature Ferromagnetic Properties of Transition Metal Implanted Al0.35Ga0.65N

Jeremy A. Raley 1Yung Kee Yeo 1Robert L. Hengehold 1Mee-Yi Ryu 1,3Todd D. Steiner 2

1. Air Force Institute of Technology (AFIT), 2950 Hobson Way, Wright-Patterson Air Force Base, OH 45433, United States
2. American Systems Corporation (ASC), Dumfries, VA 22026, United States
3. Kangwon National University, Chuncheon, Korea, South

Abstract

A 1 μm thick film of MBE-grown Al0.35Ga0.65N was implanted with Cr, Mn, and Ni at room temperature with an energy of 200 keV to a dose of 5 x 10{16) cm-2 for Cr and Mn and a dose of 3 x 1016 cm-2 for Ni. The magnetic properties of these samples were measured using superconducting quantum interference device (SQUID) magnetometry and the implantation damage recovery was evaluated using cathodoluminescence (CL). Each of these samples shows evidence of ferromagnetism when annealed under the proper conditions, and can be a viable dilute magnetic semiconductor whose ferromagnetism persists to room temperature. Thus, these samples can be good candidates for spintronic device applications.

The Cr-implanted Al0.35Ga0.65N annealed at an optimum anneal temperature of 775 oC shows the most convincing evidence of ferromagnetism persisting to room temperature with a coercive field (HC) of 249 Oe and a remanent field (BR) greater than 20% of the saturation magnetization (MS = 6 x 10-5 emu) for measurements performed at 300 K. Field-cooled (FC) and zero-field-cooled (ZFC) magnetization measurements confirm ferromagnetic properties of this sample, and the Curie temperature to be estimated at around 350 K. The optimal anneal temperature was also confirmed through CL measurements.

Al0.35Ga0.65N implanted with Mn has an HC of 199 Oe and a BR of 7 x 10-6 emu at room temperature when annealed under optimal conditions. Although temperature dependent magnetization measurements show a mild spin-glass phase, the ferromagnetic phase is clearly dominant.

Implanting Al0.35Ga0.65N with Ni produces clear ferromagnetic hysteresis at temperatures up to 350 K. However, these samples show variability of MS with respect to annealing temperature, which inhibits determination of optimal annealing conditions. FC—ZFC magnetization separation suggests the true presence of ferromagnetism in this material despite the variability in MS.

Presentation: oral at E-MRS Fall Meeting 2005, Symposium D, by Jeremy A. Raley
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-03-01 15:09
Revised:   2009-06-07 00:44
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