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X-ray Absorption Fine Structure (XAFS) techniques, namely, X-ray Near Edge Structure (XANES), Extended XAFS (EXAFS), and Anomalous X-ray Diffraction (AXRD) were used to investigate the local atomic and electronic structure of (Ga, Mn)N magnetic layers with Mn concentrations of up to 10% grown by Molecular Beam Epitaxy. The XANES and AXRD analysis prove the Mn incorporation on substitutional GaN lattice sites. EXAFS results indicate the good quality of the structure under examination, although 0.5 nitride atom vacancies were found. The Wien2k code was applied to interpret the XANES spectra quantitatively, i.e., to determine the electronic structure of the Mn atoms. It was shown that accounting for the core-hole effect is necessary to reconstruct effectively the XANES spectra. Conducted charge density analysis based on DFT calculations identified the valency of Mn atom to be of 2.4+. [ABSTRACT FROM AUTHOR]

A comprehensive characterization of the structural and magnetic properties of Fe-implanted rutile TiO2(110) is presented. Fe and FeTiO3 (ilmenite) nanocrystals (NCs) are identified by synchrotron-radiation x-ray diffraction. The majority of Fe NCs are crystallographically oriented with respect to the matrix following the relation Fe(001)[010]∥TiO2(110)[11_0]. Postannealing induced the out-diffusion of Fe and the growth of FeTiO3 at the cost of Fe NCs. Mössbauer spectroscopy and superconducting quantum interference device (SQUID) magnetometry reveal the corresponding evolution of magnetic properties, i.e., magnetization, and superparamagnetic blocking temperature. We unambiguously identify Fe NCs as the origin of the ferromagnetism. These Fe NCs possess a uniaxial in-plane magnetic anisotropy, such that the two Fe[100] axes are inequivalent. [ABSTRACT FROM AUTHOR]

We show that metallic secondary phase formation inside ZnO(0001) single crystals implant-doped with Ni at an atomic concentration of 5% can be suppressed. All the Ni ions are in the 2+ valence state after mild postannealing. The suppression is achieved by means of annealing of the crystals in high vacuum prior to implantation and is correlated with the introduction of structural disorder. The observed ferromagnetic properties of the preannealed crystals are evidently induced by defects and not primarily by the Ni doping. They degrade at ambient temperature within several days. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the correlation of the magnetism and the carrier concentration with the shift of the spectroscopic critical points for low compensated GaMnAs samples with a high Curie temperature of around 150 K. The GaMnAs layers were grown by low-temperature molecular beam epitaxy. The low-temperature annealing leads to a reduction of Mn interstitials from 0.8 to 0.4% and an enhancement in the hole concentration. The saturation magnetization is 51 emu/cm $$^3$$ and the Curie temperature is 150 K after post-growth annealing, while those of as-grown layers are 37 emu/cm $$^3$$ and 80 K. The resistivity dropped significantly after the post-growth annealing, due to the fact that the number of Mn $$_I$$ , which act as double donors and compensate holes, was significantly reduced by the low-temperature and long-time annealing. The electronic band structure is investigated by spectroscopic ellipsometry. The transition energies of critical points show redshift after post-growth annealing due to the annealing-induced enhancement of the hole concentration. Our results support the valence band picture (the Zener model) in ferromagnetic GaMnAs. [ABSTRACT FROM AUTHOR]

57Fe doped titanium oxide monocrystals, prepared by ion implantation at different temperatures and subsequent thermal treatment, were characterized by conversion electron Mössbauer spectrometry, synchrotron radiation x-ray diffraction and superconducting quantum interference device magnetometry. After implantation at room temperature Fe is present in divalent state. Upon annealing in high vacuum Fe2 + is reduced to metallic Fe for the most part. After implantation at 623 K most iron is in metallic state. During annealing on air Fe is gradually oxidized from Fe2 + to Fe3 + . Depending on preparation conditions and thermal treatment the role of different nanosized secondary phases is discussed in terms of their influence on the magnetic properties of Fe:TiO2. α-Fe nanoparticles are found to be responsible for ferromagnetism observed in TiO2. [ABSTRACT FROM AUTHOR]

The formation of secondary phases in Fe implanted GaN upon annealing in low pressure N2-atmosphere was detected by means of in situ x-ray diffraction and confirmed by magnetization measurements. A repeatable phase change from Fe3N at room temperature and Fe3-xN at 1023 K was observed in situ. The phase transformation is explained by the change of lattice site and concentration of nitrogen within nitrides. The diffusion of Fe toward sample surface and oxidation with increasing annealing cycles limits the availability of secondary phase and hence the repeatability. At high temperature GaN dissolves and Ga as well as Fe oxidize due to presence of residual oxygen in the process gas. The ferromagnetism in the samples is related to nanometer sized interacting Fe3-xN crystallites. [ABSTRACT FROM AUTHOR]

We present an experiment for the creation of unconventional ferromagnetism in pure ZnO powder by application of mechanical force. The ferromagnetism is related to flakelike structures in planar compressed pieces of the powder with easy axis in the plane. It is associated with defect creation and disappears upon annealing in oxygen. Besides cluster formation, such defects might be one of the nonintrinsic origins of ferromagnetism in transition metal doped ZnO. [ABSTRACT FROM AUTHOR]

We report on the fabrication of pseudomorphic wurtzite Ga1-xMnxN grown on GaN with Mn concentrations up to 10% using molecular beam epitaxy. According to Rutherford backscattering, the Mn ions are mainly at the Ga-substitutional positions, and they are homogeneously distributed according to depth-resolved Auger-electron spectroscopy and secondary-ion mass-spectroscopy measurements. A random Mn distribution is indicated by transmission electron microscopy, and no Mn-rich clusters are present for optimized growth conditions. A linear increase of the c-lattice parameter with increasing Mn concentration is found using x-ray diffraction. The ferromagnetic behavior is confirmed by superconducting quantum-interference measurements showing saturation magnetizations of up to 150 emu/cm3. [ABSTRACT FROM AUTHOR]

A correction to the abstract of the article titled "An easy mechanical way to create ferromagnetic defective ZnO" in the previous issue is presented.

Ion irradiation induced modifications of the thermomagnetic properties of equiatomic FeRh thin films have been investigated. The application of 20 keV Ne + ions at different fluencies leads to broadening of the antiferromagnetic to ferromagnetic phase transition as well as a shift of the transition temperature towards lower temperatures with increasing ion fluence. Moreover, the ferromagnetic background at low temperatures generated by the ion irradiation leads to pronounced saturation magnetisation at 5 K. Complete erasure of the transition, i.e. ferromagnetic ordering through the whole temperature regime was achieved at a Ne + fluence of 3 × 10 14 ions/cm 2 . It does not coincide with the complete randomization of the chemical ordering of the crystal lattice. [ABSTRACT FROM AUTHOR]

A comprehensive characterization of the structural and magnetic properties of Fe-implanted rutile TiO2(110) is presented. Fe and FeTiO3 (ilmenite) nanocrystals (NCs) are identified by synchrotron-radiation x-ray diffraction. The majority of Fe NCs are crystallographically oriented with respect to the matrix following the relation Fe(001)[010]∥TiO2(110)[11_0]. Postannealing induced the out-diffusion of Fe and the growth of FeTiO3 at the cost of Fe NCs. Mössbauer spectroscopy and superconducting quantum interference device (SQUID) magnetometry reveal the corresponding evolution of magnetic properties, i.e., magnetization, and superparamagnetic blocking temperature. We unambiguously identify Fe NCs as the origin of the ferromagnetism. These Fe NCs possess a uniaxial in-plane magnetic anisotropy, such that the two Fe[100] axes are inequivalent. [ABSTRACT FROM AUTHOR]