ABSTRACT

Abstract. We performed a detailed study of growth and magnetic characterization of Gd doped GaN. Our study reveals an unprecedently large magnetic moment of Gd in GaN which is arising from a long range spin polarization of the GaN matrix by the Gd atoms. As a direct result of this effect, the material is found to exhibit ferromagnetism above room temperature. The combination of these two effects may open up a new window of opportunity to overcome the long lasting hurdle to achieve efficient spin-injection into semiconductor structures, a very important criterion for developing future spintronic devices. 12

1. Introduction GaN based diluted magnetic semiconductors (DMS) have the potential for exhibiting high temperature ferromagnetism which is very important for developing future spintronic devices. Several transition metal (TM) doped GaN DMS have been investigated. Roomtemperature ferromagnetism in these materials, however, is often found to result from the formation of precipitates rather than from a homogeneous alloy. The rare-earth (RE) elements could be an interesting alternative to transition metals. RE atoms have partially filled / - orbitals which carry magnetic moments and may take part in magnetic coupling like in the case of TM with partially filled ^-orbitals. While it is expected that the magnetic coupling strength of /-orbitals is much weaker than that of <i-orbitals due to the stronger localization of the /-electrons, Gd is the only RE element which has both partially filled 4 / and 5c/-orbitals. Together these orbitals can take part in a new coupling mechanism proceeding via intra-ion 4f-5d exchange interaction followed by inter-ion 5d-5d coupling mediated by charge carriers [1]. Here, we performed a systematic study of growth and magnetic characterization of several Gd-doped GaN layers. Our study reveals an extraordinarily large magnetic moment of Gd in GaN. The material is also found to exhibit ferromagnetism above room temperature.