Dresden 2009 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 24: Magnetic Semiconductors

MA 24.7: Vortrag

Mittwoch, 25. März 2009, 16:15–16:30, HSZ 401

DMS GaMnN/AlGaN heterostructures — •Till Benter, Dong-Du Mai, Arne Urban, Joerg Malindretos, Michael Seibt, and Angela Rizzi — IV. Physikalisches Institut, Georg-August Universität Göttingen, 37077 Göttingen, Germany

GaMnN is a prototype GaN-based dilute magnetic semiconductor. Our earlier work showed only weak ferromagnetic coupling of single layer systems at room temperature with a saturation magnetisation of M_S = 0.025 µ_B/Mn and a small coercive field of 250 Oe, which leads to the assumption that only a small fraction of the incorporated Mn-ions participate in the ferromagnetic coupling. As an alternative system AlGaN/GaMnN/AlGaN heterostructures have been grown. The magnetization as well as the coercive field are strongly increased in these samples and the results are well reproducible. A TEM analysis exhibits regions of high Mn concentration at the upper heterojunction, which could be responsible for the coercivity. Mechnanical strain, polarization charges and diffusion barriers at the heterojunctions seem to influence the Mn incorporation into the GaN matrix. Diverse heterostructure configurations have been characterized concerning the magnetic and structural properties and the results are discussed with reference to the assumed double-exchange mechanism for the magnetic coupling.