Optical Behavior of III-TM-N Materials and Devices
FLORIDA UNIV GAINESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
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Room temperature ferromagnetism has been observed in AlMnN grown by gas-source MBE. The lattice constant decreased with increasing Mn cell temperature for single phase material, indicating constant site occupation, probably substitutional. Hysteresis in M vs. H at room temperature was observed in single phase material and the magnetization as a function of temperature suggests ferromagnetism caused by AlMnN, not clusters. AlCrN was also investigated. Strong ferromagnetism persists to 350K the temperature limit of the SQUID magnetometer, in the optimized AlCrN. Moreover, the saturation magnetization remains unchanged in the temperature region from 10K-350K. By contrast, AlMnN films grown under similar conditions were found to decrease in magnetization at 300K as compared to 100K. This suggests that AlCrN has a Curie point above that of AlMnN. Moreover, the Curie temperature of AlCrN is well above room temperature whereas the Curie temperature of AlMnN is in the vicinity of room temperature. Overall, Cr tends to be a better dopant than Mn in ferromagnetic AlN. The thermal stability of optimal epi-AlCrN was investigated and was found to be poorer than that of GaCrN. The upper limit of anneal temperature before destruction of magnetic properties was found to be 700 deg C. No indication of second phases was observed after the 700 deg C anneal, which implies that the RTA was not significant enough to destroy the single phase AlCrN. However, although the single phase AlCrN withstood the RTA, the magnetic interaction within the material did not. This suggests that the mechanism for magnetization within this particular DMS is too weak to endure routine processing procedures during fabrication, such as the annealing of ohmic contacts. Hence, processing procedures must be altered for incorporation into current technology or alternate materials will need to be used in place of AlCrN.
- Physical Chemistry