Volume 95, Issue 2, 15 January 2004
Index of content:
- MAGNETISM AND SUPERCONDUCTIVITY (PACS 74-76)
95(2004); http://dx.doi.org/10.1063/1.1633340View Description Hide Description
epilayers with a well-ordered ferromagnetic structure were grown on sapphire (0001) substrates, using the plasma enhanced molecular-beam epitaxy technique. films were found to be homogeneous, and to exhibit -type conductivity and ferromagnetic ordering with a Curie temperature above room temperature. This was confirmed by transmission electron microscopy,x-ray diffraction, and by magnetometry using a superconducting quantum interference device. The high-temperature photoluminescence(PL) spectra exhibited Mn-related free-to-acceptor pair transitions for layers with and A Mn acceptor level of a layer with low Mn content was found to be located around 330 meV above the top of the valence band, suggesting that Mn-bound holes in group-III nitrides exhibit effective-masslike behavior. The excitation and temperature-dependentPL provided convincing evidence of a band-edge exciton to acceptor transition.
95(2004); http://dx.doi.org/10.1063/1.1632016View Description Hide Description
Fe/Cr/Fe trilayers were epitaxially grown on atomically flat GaAs(001). For the thickness of Cr spacer layer corresponding to antiferromagnetic coupling, “reversed” minor hysteresis loops were measured with longitudinal magneto-optical Kerr effect(MOKE), i.e., a negative “magnetization” signal was detected when the thicker bottom Fe layer was saturated along the applied field. This behavior is interpreted by depth variations of the MOKE sensitivity. Magnetization reversal shows that both antiferromagnetic switching and spin–flop transition fields depend on the ratio of both Fe film thicknesses. The shape of the MOKE loops becomes more complex with further deposition of MgO and Fe layers on the top of the Fe/Cr/F/GaAs(001) stack. Superconducting quantum interference device measurements confirm the interpretation of the MOKE loops and demonstrate homogeneity and sharpness of the interfaces in the structures.
95(2004); http://dx.doi.org/10.1063/1.1634390View Description Hide Description
Structural investigation of as-grown as well as annealed epilayers was carried out using high-resolution x-ray diffraction(XRD)measurements for a wide range of Mn concentrations with special attention on how the interstitial Mn atoms influence the lattice parameter of this material. We observe a distinct decrease of the lattice parameter after low-temperature annealing of which is known to reduce the concentration. The reciprocal space maps measured for all of the investigated samples showed that the layers are fully strained—i.e., they remain pseudomorphic to the GaAs (001) substrate—for the entire thickness of the samples used (in the present case over 100 nm). In all cases studied, the XRDmeasurements revealed high crystalline perfection of both as-grown as well as annealed epilayers.
95(2004); http://dx.doi.org/10.1063/1.1635978View Description Hide Description
We investigated the microscopic structure of FePtCu ternary ordered alloys from both theoretical and experimental points of view. From the theoretical viewpoint, first principles calculation was carried out based on the full-potential linear augmented plane wave method in order to obtain the electronic structure and magnetic anisotropy energy of the FePtCu ternary ordered alloy. From the experimental viewpoint, the ultraviolet photoelectron spectroscopy measurement was used to identify the Cu position in FePtCu ternary ordered alloy. From a comparison with the calculated density of states curve, it was found that the Fe site of FePt ordered alloy replaced the Cu. The theoretical and experimental results in this article support the mechanism proposed in terms of the thermodynamic considerations in our previous article.