Magnetic properties of GaMnAs single layers and GaInMnAs superlattices investigated at low temperature and high magnetic field

Magnetotransport properties of GaMnAs single layers and InGaMnAs/InGaAs superlattice structures were investigated at temperatures from 4 K to 300 K and magnetic fields up to 23 T to study the influence of carriers confinement through different structures. Both single layers and superlattice structures show paramagnetic-to-ferromagnetic phase transition. In GaMnAs/InGaAs superlattice beside the Curie temperature (Tc ~ 40 K), a new phase transition is observed close to 13 K.Comment: 8 pages, 5 figures, Proceedings of the XXXII International School on the Physics of Semiconducting Compounds, Jaszowiec 2003, Polan

Post-growth annealing of GaMnAs under As capping - an alternative way to increase Tc

We demonstrate that in situ post-growth annealing of GaMnAs layers under As capping is adequate for achieving high Curie temperatures (Tc) in a similar way as ex situ annealing in air or in N2 atmosphere practiced earlier.Comment: 13 pages, 4 figure

Magnetic properties of Ce

The magnetic susceptibility of Pb1-xCexA (A = S, Se and Te) crystals with 0.006 ≤  x ≤ 0.036  were studied in the temperature range from 20 mK up to room temperature. X-band (~9.5 GHz) Electron Paramagnetic Resonance (EPR) showed small shifts in the effective Landé factors that were attributed to crystal-field admixture. The EPR measurements were correlated with the magnetic susceptibility data and resulted in estimating the crystal-field splitting Δ = E(Γ8) - E(Γ7) of the lowest 2F5/2 manifold for Ce3+ ions in PbA (A = S, Se and Te) of about 340 K, 440 K and 540 K for Pb1-xCexTe, Pb1-xCexSe, and Pb1-xCexS, respectively. The values for the crystal-field splitting deduced from the magnetic data were found to be in agreement with the calculated ones based on the point charge model. Moreover, the deHaas van-Alphen magnetic oscillations in the susceptibility measurements of Pb1-xCexTe (x~ 0.05 and 0.07) were observed at ultra-low temperature (20 mK); The oscillations were investigated and the values of the oscillatory period for Pb1-xCexTe (x = 0.0048 and 0.007) are reported

Antisymmetric magnetoresistance anomalies and magnetic domain structure in GaMnAs/InGaAs layers

Antisymmetric magneto-resistance anomalies generated by a reversal of the magnetization are studied in a number of GaMnAs/InGaAs layers with out-of-plane (easy axis) magnetization. The anomalies occur independent of the magnetic field orientation. This shows, that once a magnetic domain with reversed magnetization is nucleated, simply the presence of the domain wall between the longitudinal contacts is sufficient to give rise to the anomaly. Very different shapes for magneto-resistance anomaly can be observed experimentally depending upon the sample. They reflect the various magnetic domain structures present inside the layers during the magnetization reversal process

Magnetotransport properties of short period GaMnAs/InGaAs superlattices

Magnetotransport properties of GaMnAs/InGaAs superlattice structure and GaMnAs/GaAs single layers have been investigated from 4 to 300 K and magnetic fields up to 22.5 T. All these magnetic semiconductors show the so-called "paramagnetic-to-ferromagnetic phase transition''. However, in GaMnAs/InGaAs superlattice beside the Curie Wiess temperature (T-c similar to 40 K), a new phase transition is observed close to 13 K. (C) 2004 Elsevier B.V. All rights reserved