We have succeeded in realizing room-temperature ferromagnetism in a novel magnetic semiconductor (Cd,Mn)GeP2.
The starting material was a single crystal bulk of CdGeP2, which belongs to II-IV-V2 chalcopyrite semiconductor family. Mn was deposited in MBE chamber and thermally diffused. RHEED before and after Mn-doping showed a distinct pattern charcteristic of 112 plane of tetragonal chalcopyrite structure. The EDX measurement revealed about 30% of Cd was replaced by Mn at the surface region. No trace of binary phase was found by accurate X-ray measurements.
Well-defined hysteresis loop with coersive field of 400 Oe was found at room temperature. The temperature dependence of magnetization was measured from which Curie temperature was determined to be 320K. The surface observation by MFM showed a stripe domain pattern at room temperature. Photoluminescence spectrum at 20K showed a peak at 3.24eV, in addition to the emission line around 1.7eV related to band gap of the host CdGeP2. This suggests that the new material is a semiconductor with the band gap twice as large as the host. Magneto-optical Kerr ellipticity showed a peak at the band edge region of CdGeP2.
We believe we have found for the first time a magnetic semiconductor with Curie temperature above room temperature.
The finding is highly appreciated by Dr. Stuart A. Wolf (Naval Research Laboratory, USA) at Int Conf on Physics and AQpplication of Spin-Related Phenomena in Semiconductors (PASPS2000) held at Sendai(Japan) that this discovery is very important for spintronics for next generation. The details of the present results has been published as the Express Letter paper in Japanese Journal of Applied Physics vol.39 Part 2, No.10A, pp.L949-L951 (2000).
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