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Bulk Zn1-xCoxO samples were synthesized via standard solid-state reaction route with different Co molar concentrations up to 21%. A detailed microstructural analysis was carried out to investigate alternative sources of ferromagnetism, such as secondary phases and nanocrystals embedded in the bulk material. Conjugating different techniques we confirmed the Zn replacement by Co ions in the wurtzite ZnO structure, which retains, however, a high crystalline quality. No segregated secondary phases neither Co-rich nanocrystals were detected. Superconducting quantum interference device magnetometry demonstrates a paramagnetic Curie–Weiss behavior with antiferromagnetic interactions. We discuss the observed room temperature paramagnetism of our samples considering the current models for the magnetic properties of diluted magnetic semiconductors. [ABSTRACT FROM AUTHOR]

Presents a study that have grown ferromagnetic perpendicularly magnetized epitaxial thin films of aluminum on aluminum arsenide/gallium arsenide heterostructures by molecular beam epitaxy. Polar Kerr rotation of manganese-aluminum and aluminum; Magnetization of manganese-aluminum and aluminum; Achievement of the largest polar Kerr rotation.

We investigated the effects of Mn ions on the spin dynamics of electrons confined in a semiconductor quantum well nearby a Mn-based ferromagnetic layer. Circularly polarized Hanle and time-resolved photoluminescence (PL) measurements were carried out on a set of samples with different Mn delta-doping concentrations. We observe a strong influence of the Mn layer for both the electron lifetime and its spin-relaxation time for high-Mn concentrations, when the electrons significantly overlap with Mn ions. Our results also show that the circular-polarization degree obtained by simple continuous-wave PL measurements is not sufficient to determine the relaxation dynamics due to a compensation effect of the lifetime and the spin-relaxation time. (Some figures may appear in colour only in the online journal) [ABSTRACT FROM AUTHOR]

Ferromagnetic clusters were incorporated into GaAs samples by Mn implantation and subsequent annealing. The composition and structural properties of the Mn-based nanoclusters formed at the surface and buried into the GaAs sample were analyzed by x-ray and microscopic techniques. Our measurements indicate the presence of buried MnAs nanoclusters with a structural phase transition around 40 °C, in accord with the first-order magneto-structural phase transition of bulk MnAs. We discuss the structural behavior of these nanoclusters during their formation and phase transition, which is an important point for technological applications. [ABSTRACT FROM AUTHOR]