Room Temperature Ferromagnetism in Gadolinium-doped Gallium Nitride
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.11
Room Temperature Ferromagnetism in Gadoliniumdoped Gallium Nitride Vishal G. Saravade, Cameron H. Ferguson, Amirhossein Ghods, Chuanle Zhou and Ian T. Ferguson Missouri University of Science and Technology, Rolla, MO 65409, U.S.A.
ABSTRACT
Anomalous Hall effect was observed at room temperature in MOCVD-grown GaGdN from a (TMHD)3Gd source, which can contain oxygen in its organic ligand. GaN, and GaGdN grown using a Cp3Gd precursor which does not contain oxygen only showed the ordinary Hall effect. This indicates that oxygen could have a role in magnetic properties of GaGdN. The relationship between the anomalous Hall conductivity and longitudinal conductivity indicated that metallic conduction, hopping of carriers, and scattering-independent mechanisms are likely responsible for the ferromagnetism. However, this still requires further clarification.
INTRODUCTION Spintronics has the potential to produce smaller devices with higher speed, lower power consumption and additional functionality compared to the current electronic or optoelectronic technology [1]. Dilute magnetic semiconductors (DMS) materials, which are semiconductors doped with transition metal or rare earth elements and exhibit both ferromagnetic and semiconductor properties, are being explored due to their potential ability to enable the development of spintronic devices [2-4]. GaN based DMS materials have been investigated as a possible material system that exhibits ferromagnetism at room temperature (RT) [2-4]. GaMnN has shown ferromagnetic behavior, however Mn forms deep defect levels in GaN and results in resistive samples that are typically not suitable to be used in devices [5-8]. There has been a recent interest in Gd-doped GaN after the observation of colossal magnetic moment in GaGdN grown on SiC using MBE [8]. These samples were resistive and the ferromagnetism did not seem to be carrier mediated. However, conductive GaGdN which also exhibited ferromagnetism has been grown using MOCVD. The saturation magnetization was enhanced with an increase in carrier density making carrier mediated mechanism most likely responsible for this ferromagnetism [9]. In addition, there is evidence that oxygen interstitials could possibly affect magnetic properties of GaGdN by p-d and/or p-f hybridization with the dopant’s partially filled orbitals [10]. However, Ga vacancies and crystal defects can also contribute to ferromagnetism in GaGdN [2,11,12]. At this time, the origin of ferromagnetism in GaGdN is still not clear. Anomalous Hall effect (AHE) measurements can provide some insight into the mechanism responsible for the ferromagnetism. AHE due to intrinsic mechanism is
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based on the band structure of the material while extrinsic mechanism is dependent
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