We show that by annealing Ga 1-x Mn x As thin films at temperatures significantly lower than in previous studies, and monitoring the resistivity during growth, an unprecedented high Curie temperature T C and conductivity can be obtained. T C is unambiguously determined to be 118 K for Mn concentration x=0.05, 140 K for x=0.06, and 120 K for x=0.08. We also identify a clear correlation between T C and the room temperature conductivity. The results indicate that Curie temperatures significantly in excess of the current values are achievable with improvements in growth and post-growth annealing conditions.

Vanishing of ferromagnetic order in (Ga,Mn)As films at high hole concentrations: beyond the mean field Zener model J. Appl. Phys. 103, 07D132 (2008); 10.1063/1.2836330Highly enhanced Curie temperature in low-temperature annealed [Ga,Mn]As epilayers Hall effect and magnetic properties of III-V based ( Ga 1−x Mn x ) As/AlAs magnetic semiconductor superlattices

Tunneling spectroscopy studies on oxidized and bare surfaces of icosahedral i-AlPdRe, i-AlCuFe, and approximant a-AlMnSi phases reveal specific features of the density of states (DOS) close to the Fermi level as compared to the crystalline nonapproximant v-AlCuFe phase. The Fermi energy lies in the middle of a narrow pseudogap of about 50 meV width. For higher energies, the DOS exhibits a square root energy dependence attributed to electron-electron interaction effects. The DOS differs from the linear muffin tin orbital calculated DOS and the possible roles of electron scattering and inhomogeneous electronic structure close to the surface are discussed.[S0031-9007(96)

We present measurements on hybrid ferromagnetic/semiconductor devices. Single, submicron ferromagnetic structures have been fabricated directly onto the surface of a semiconductor, which incorporates a near-surface two-dimensional electron gas (2DEG). The induced Hall resistance and magnetoresistance of the 2DEG are used to measure the magnetic properties of the stripes directly. The relative merits of these two techniques are compared using a device geometry in which both types of measurement can be made simultaneously.