Extensive Kerr microscopy studies reveal a strongly temperature dependent domain wall dynamics in Hall-bars made from compressively strained GaMnAs. Depending on the temperature magnetic charging of domain walls is observed and nucleation rates depen
d on the Hall-geometry with respect to the crystal axes. Above a critical temperature where a biaxial-to-uniaxial anisotropy transition occurs a drastic increase of nucleation events is observed. Below this temperature, the nucleation of domains tends to be rather insensitive to temperature. This first spatially resolved study of domain wall dynamics in patterned GaMnAs at variable temperatures has important implications for potential single domain magneto-logic devices made from ferromagnetic semiconductors.
The magnetism of quench-condensed Ru and Rh impurities and metal films on Ag(100) and Pt(997) has been studied using x-ray magnetic circular dichroism. In the coverage range between 0.22 ML and 2.0 ML no dichroic signal was detected at the M3,2 absor
ption edges of Ru on Ag(100) at a temperature of 5 K in the presence of an applied magnetic field. The same was found for coverages between 0.12 ML and 0.5 ML of Rh on Ag(100) and Pt(997). It is concluded that the magnetic moments of single impurities, small clusters of various shape and monolayers of the 4d metals are below the detection limit of 0.04 muB per atom. These results provide an unambiguous determination of the local magnetic moment of Ru and Rh deposited on nonmagnetic transition-metal surfaces, which are in contrast with theoretical predictions.
