Room Temperature Electron-Mediated Ferromagnetism in a Diluted Magnetic Semiconductor: (Ga,Mn)N

Room-temperature ferromagnetism of (Ga,Mn)N films: effects of Ga flux and growth temperature

“…On the other hand, the films grown at Ga effusion cell temperatures of 970 C and 980 C have relatively low Mn concentration. As mentioned in previous report [10], saturation magnetizations of (Ga,Mn)N films depend on Mn concentration in the films. Therefore, as the Ga effusion cell temperature increases, Mn concentration decreases due to the competition of Ga and Mn, which results in decrease of saturation magnetization of the films.…”

“…It is obvious that the hysteresis loops indicate ferromagnetic ordering at room temperature for all the samples with Ga effusion cell temperature range of 950-980 C. Ga effusion cell temperature dependence on magnetic behavior of (Ga,Mn)N films was observed in the films grown at Ga effusion cell temperatures of (a) 950 C, (b) 960 C, (c) 970 C, and (d) 980 C. The inset in Fig. 4 shows that the saturation magnetization (M s ) of the (Ga,Mn)N films decreases with increasing Ga effusion cell temperature and is saturated to B2.0 emu/cm 3 above Ga effusion cell temperature of 970 C. The Mn concentration in the (Ga 1Àx Mn x )N films was estimated using the total magnetic moment of each Mn atom [10]. For the film grown at Ga cell temperature of 950 C, the mole fraction of Mn is 0.007 while, for the film grown at Ga cell temperature of 980 C, it decreases to 0.005.…”

“…However, saturation magnetization of (Ga,Mn)N film grown at 550 C, B2.9 emu/cm 3 , is much higher than that of the film grown at 750 C. It is due to the high Mn concentration in the film grown at low temperature. The Mn concentrations in the (Ga 1Àx Mn x )N films determined by using the total magnetic moment of each Mn atom [10] are x ¼ 0:007 for the film grown at 550 C and x ¼ 0:005 for the film grown at 750 C. From the XRD and AGM results, we have known that the Mn concentration in (Ga,Mn)N films increases, and the magnetic properties are improved with decreasing growth temperature.…”

“…Wide bandgap semiconductors are of particular importance with respect to Curie temperature, since Dietl et al [6] predicted that T C of GaN and ZnO can be higher than room temperature on the basis of the mean-field Zener model of ferromagnetism. On the basis of this theory, p-type (Ga,Mn)N [7,8] and n-type (Ga,Mn)N [9,10] DMSs with T C exceeding room temperature have been recently reported.…”

“…In previous reports [10,11], we have presented that (Ga,Mn)N films exhibited room temperature ferromagnetism due to the coupling of electron spins and localized Mn moments and that the magnetic properties of the films were enhanced as Mn effusion cell temperature increases using plasma-enhanced molecular beam epitaxy (PEMBE). In this paper, we report on the room temperature ferromagnetism, structural and electrical properties in the epitaxial (Ga , Mn)N films grown on sapphire substrate with the variation of Ga flux and growth temperature in PEMBE system.…”