Epitaxial thin films of Mn3−xCoxGa were grown on MgO by magnetron co-sputtering with different Co content. Dependent on the Co content tetragonal or cubic structures are obtained. The composition dependence of saturation magnetization MS and uniaxial magnetic anisotropy Ku in the epitaxial films were investigated. A high magnetic anisotropy Ku of 1.2 MJ m−3 was achieved for the Mn2.6Co0.3Ga1.1 film with low magnetic moment of 0.84 μB. The valence band spectra of the films were investigated mainly by hard x-ray photoelectron spectroscopy. The evidence of sharp states in the cubic case, which are smeared out in the tetragonal case, proof the existence of a van Hove singularity that causes a band Jahn-Teller effect accompanied by a tetragonal distortion. These differences are in well agreement to the ab-initio calculations of the electronic structure.
We grew a magnetic tunnel junction (MTJ) with a top electrode consisting of a Mn3Ge film using a thin Co–Fe alloy film as a seed layer. X-ray diffraction showed that the Mn3Ge had (001)-oriented D022 structure epitaxially grown on an MgO(001) substrate. Magnetic hysteresis loops suggested that the D022-Mn3Ge film possessed perpendicular magnetic anisotropy. A magnetoresistance (MR) ratio of 11.3% was observed in the microfabricated MTJ at room temperature. The resistance–field curve suggested that the top-Co–Fe and D022-Mn3Ge layer are weakly coupled antiferromagnetically. The optimization of top-Co–Fe composition would improve MR ratio.
Ferromagnetic resonance (FMR) was measured for Cu/permalloy (Py) (20, 30, 40 \AA{})/Cu ${(d}_{\mathrm{Cu}})/\mathrm{Pt}$ (0, 50 \AA{}) films with various ${d}_{\mathrm{Cu}}$ to clarify the effect of spin diffusion driven by the precession of magnetization on Gilbert damping. The peak-to-peak linewidth $\ensuremath{\Delta}{H}_{\mathrm{pp}}$ of the FMR spectra for Cu/Py/Cu/Pt films was very large at ${d}_{\mathrm{Cu}}=0\mathrm{\AA{}},$ and decreased remarkably at ${d}_{\mathrm{Cu}}=30\mathrm{\AA{}}.$ Above ${d}_{\mathrm{Cu}}=30\mathrm{\AA{}},$ it decreased gradually with increasing ${d}_{\mathrm{Cu}}$ in the anomalously wide range of ${d}_{\mathrm{Cu}}.$ The out-of-plane angular dependence of the FMR of Cu/Py(30 \AA{})/Cu ${(d}_{\mathrm{Cu}})/\mathrm{Pt}$ (0, 50 \AA{}) films was measured and analyzed using a Landau-Lifshitz-Gilbert equation that took into account the local variation of the effective demagnetizing field. The Gilbert damping coefficient G obtained from the analysis for Cu/Py/Cu/Pt films was about twice as large as that for Cu/Py/Cu films even at ${d}_{\mathrm{Cu}}=100\mathrm{\AA{}}$ and decreased gradually as ${d}_{\mathrm{Cu}}$ increased. At ${d}_{\mathrm{Cu}}=2000--3000\mathrm{\AA{}},$ G for Cu/Py/Cu/Pt and Cu/Py/Cu films has the same value. We discussed the influence of spin diffusion driven by the precession of magnetization in FMR on G using a previously proposed model. The calculated G vs ${d}_{\mathrm{Cu}}$ fitted well to the experimental one, and the other features of the experimental results are well explained by the model.
Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.
We investigate local THz field generation using spintronic THz emitters to enhance the resolution for micrometer-sized imaging. Far-field imaging with wavelengths above 100 μm limits the resolution to this order of magnitude. By using optical laser pulses as a pump, THz field generation can be confined to the area of laser beam focusing. The divergence of the generated THz beam due to laser beam focusing requires the imaged object to be close to the generation spot at a distance below the THz field wavelength. We generate THz-radiation by fs-laser pulses in CoFeB/Pt heterostructures, based on spin currents, and detect them by commercial low-temperature grown-GaAs (LT-GaAs) Auston switches. The spatial resolution of THz radiation is determined by applying a 2D scanning technique with motorized stages allowing step sizes in the sub-micrometer range. Within the near-field limit, we achieve spatial resolution in the dimensions of the laser spot size on the micrometer scale. For this purpose, a gold test pattern is evaporated on the spintronic emitter separated by a 300 nm SiO2 spacer layer. Moving these structures with respect to the femtosecond laser spot, which generates THz radiation, allows for resolution determination. The knife-edge method yields a full-width half-maximum beam diameter of 4.9±0.4 μm at 1 THz. The possibility to deposit spintronic emitter heterostructures on simple glass substrates makes them attractive candidates for near-field imaging in many imaging applications.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The influence of annealing temperature and film thickness on structural and magnetic properties of Mn 2.5 Ga films were investigated in this work. The annealing temperature of 400°C was found to be the optimum condition to obtain the films with high perpendicular magnetic anisotropy (PMA) (K ueff = 7.8 × 10 6 erg/cm 3 ) and smooth surface (R a ¿ 0.15 nm). The PMA property was maintained in the 5 nm thick film, and deterioration of the PMA properties with decreasing film thickness can be ascribed to the tensile strain existed in the thin Mn 2.5 Ga films.
