Room temperature ferromagnetism in novel diluted magnetic semiconductor Cd1-xMnxGeP2

High concentration of Mn atoms has been incorporated in the surface region of II-IV-V-2 type chalcopyrite semiconductor CdGeP2. Photoluminescence spectrum at 20 K shows a peak around 3.2 eV, suggesting that the incorporation of Mn introduces an energy gap much higher than that of the host semiconductor (E-g = 1.83 eV). Prominent magnetic hysteresis loops with coercivity of 0.5 kOe has been observed at room temperature. Magnetic force microscope (MFM) measurements reveal a stripe-shaped domain pattern on the top surface. Magneto-optical Kerr ellipticity spectrum measured at room temperature show a prominent peak at 1.7 eV and a broad tail up to 3.5 eV. We tentatively attribute the ferromagnetism to the double exchange interaction between Mn2+ and Mn3+ states due to the structural feature of II-IV-V-2 type chalcopyrite compounds.