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Abstract: M-type barium ferrite thin films were deposited onto sapphire (00l) substrates by radio frequency magnetron sputtering. Columnar grains were formed on the surface of the films under lower sputter pressure with bubble magnetic domains, which is originated from high magnetocrystalline anisotropy of the film. Magnetic hysteresis loops agree with the change of the morphology, where in-plane and out-of-plane loops are quite different of the samples prepared under high sputtering pressures, while they are almost identical under low pressures. The influence of the sputtering pressure was understood by that with the increase of the pressure, resputtering of the film is hindered. Nucleation with c-axis normal to the film plane was enhanced. Thus samples prepared under low pressure have more acicular crystallites which have c-axis parallel to the film plane. [Copyright &y& Elsevier]

Abstract: M-type barium ferrite thin films were deposited onto sapphire (00 l) substrates by radio frequency magnetron sputtering. An ultra-thin layer about 20nm was deposited and annealed before continuous deposition of the films up to 500nm under different sputtering pressures: 0.2, 0.5, 0.8 and 1.0Pa, respectively. It was found that the atomic ratios of Fe to Ba increased from 9.3 to 15.0 with the increase of the pressure. The films sputtered at all pressures have c-axis normal to the film plane by a four circle X-ray diffractometer, which is an improvement of the films directly sputtered on the substrate. Needle-like grains were formed on the surface of the films under higher sputter pressure with bubble domains, which is originated from high magnetocrystalline anisotropy of the film. Magnetic hysteresis loops recorded by vibrating sample magnetometer agree with them, where in-plane and out-of-plane loops of the samples prepared under high sputtering pressures are quite different, while they are almost identical of the samples under low pressures. The influence of the sputtering pressure was understood by that with the increase of the pressure, resputtering of the films was increased. Nucleation with c-axis normal to the film plane was deteriorated. Thus samples prepared under high pressure have more needle-like crystallites which have c-axis parallel to the film plane. [ABSTRACT FROM AUTHOR]

Abstract: Hexagonal barium ferrite thin films were fabricated by spin coating of precursors obtained by sol-gel methods onto sapphire (00l) faces. Citric acid and ethylenediaminetetraacetic acid (EDTA) were used to tune the morphology of the films. The films show texture with c-axis normal to the film plane as shown by the strong x-ray diffractions from the (001) plane with full width at half maximum of the rocking curves about 0.4°. The [100] direction of the film is parallel to the [110] direction of the sapphire. With the increase of the citric acid, the percentage of the acicular crystallites increased. EDTA can be used to produce films with the best texture where faceted grains were obtained. The maximum coercive force obtained was about 302 kA/m. [Copyright &y& Elsevier]

Abstract: Barium ferrite films were prepared by spin-coating of gels on sapphire (00 l) faces. Ethylenediaminetetraacetic acid was used to bind the metal ions. Thin films prepared by this method show faceted hexagonal grains with c-axis normal to the film plane and [110]sapphire ||[100]film. Needle-like grains, which have c-axis in the film plane, are minimized. Epitaxial growth of the film can be observed by the high resolution images. Reduction of the a and c-axis of the film compared with those of the bulk materials is confirmed both in real space and reciprocal space. Magnetic hysteresis loops were recorded in-plane and out-of-plane. The film shows uniaxial anisotropy as exemplified by branched domains with coercivity field of 87.6kA/m along the in-plane direction and of 302.5kA/m along the out-of-plane direction. [Copyright &y& Elsevier]

• Distribution of induced microwave current in Py film depends on its geometry. • SRE signal can be neglected at specific magnetic field angle and geometry for Py film. • Pure ISHE signal can be obtained directly in Py(20 nm)/Ta(10 nm) bilayer (40 μm × 8 mm). • Spin Hall angle value of Ta in Py/Ta bilayer is similar to that of some literatures. We present a method to directly obtain the pure inverse spin Hall effect (ISHE) signal without the spin rectification effect (SRE) signal in ferromagnetic metal(FM)/nonmagnetic metal(NM) bilayers. This method is based on a fact that the distribution of the induced microwave current is largely dependent on the geometries of the samples. The ISHE signal can be maximized through shaping the samples and tuning the magnetic field directions, while the SRE signal can be minimized below the detection limit. This provides also a fast and simplified method to measure the ISHE signal in a wide frequency range. The spin Hall angle of Ta in a Py/Ta bilayer is −0.027 ± 0.015 in a wide frequency range. [ABSTRACT FROM AUTHOR]

Noble metal Pt with the face-centered-cubic structure is distorted to tetragonal and orthorhombic structures in order to mimic thin films grown on flexible substrates and bending. The electronic structures from the fully relativistic treatment of the kinetic terms were obtained and followed by projecting the extensive states into the localized Wannier orbitals with a minimum basis. The spin Hall conductivity (SHC) was then obtained with the help of the concept of the Berry curvature. We find that tensile strains in-plane can enhance the SHC while the compressive ones reduce the σ x y z component of the SHC. The variation of SHC can be as large as 8.6% for every 1% of the strains. Our work shows the possibility of tuning the SHC in metals, which can be utilized in spintronic devices. • The spin-to-charge conversion efficiency in Pt thin films can be enhanced by deformations. • The sensitivity of the spin Hall conductivity can be as large as 8.6% for every 1% of strains. • The underlying mechanism is the electronic band deformations. [ABSTRACT FROM AUTHOR]

Abstract: Hexagonal barium ferrite (BaFe12O19) thin films were fabricated by spin coating of precursors from sol–gel methods. Different amount of citric acid was added. Weight loss and changes of chemical bonds during the heat treatment below 500°C were recorded by thermogravity analyzer and Fourier transform infrared spectroscopy, respectively. The morphology of the films, i.e. the amount of acicular crystallites in the film, was controlled by adjusting the quantity of citric acid. The X-ray diffraction shows that the films are c-axis oriented, but the crystallization is less perfect with the increase of the citric acid. With the increase of the citric acid, the percentage of the acicular crystallites increased. At the same time, the coercivity force increased. The acicular crystallites were not exchange-coupled to the platelet crystallites. The citric acid was understood to form complex with iron ions and accelerate the exothermal auto-combustion. The c-axis oriented growth of the film was thus deteriorated. [ABSTRACT FROM AUTHOR]

We measured the spin rectification effect and the inverse spin Hall effect in Nb-doped SrTiO 3 by pumping the spins from the ferromagnetic thin films into SrTiO 3. The spin injection is increased when the doping level is increased. However, the spin to charge conversion efficiency which is measured by the spin Hall angle decreases when Nb concentration is more than ∼ 0.02 wt%. We argued that it is because that the electrons contributed to the inverse spin Hall effect are from the d − orbitals of Nb instead of Ti beyond this concentration. Our work points to the importance of orbital occupations in the (inverse) spin Hall effect. We may explore controllable spin and charge interconversion in oxide spintronics. • The spin currents can be converted into the charge current in Nb doped SrTiO 3. • The conversion efficiency is a function of the doping levels • The underlying mechanism is the multiorbital nature of the d-electrons [ABSTRACT FROM AUTHOR]

Abstract: Barium ferrite thin films have been prepared by radio frequency magnetron sputtering on a sapphire (001) substrate at substrate temperature of 500°C and 650°C, respectively. The films were further annealed in air at 1000°C for 5h. X-ray diffraction shows that the films at the lower substrate temperatures have a good epitaxial relation with respect to the substrate, while the samples under the higher substrate temperatures have (109) planes parallel to the substrate. The remanence ratio decreases from 0.82 to 0.47 when the substrate temperature is increased. We attribute the variation of the growth direction to the enhanced vertical mobility of the deposited atoms when the substrate temperature is increased. [Copyright &y& Elsevier]

• Anisotropical diffusion of incident atoms leads to non-uniform thickness of films. • Films on pyramid substrates have smaller M s but larger H c than that of on flat substrate. • Coercivities of all the films on mono-like cast silicons are highly angular dependent. • Surface structure of substrates dominantly affects the magnetic properties of films. The microstructure and magnetic properties of Ta/Ni 81 Fe 19 /Ta tri-layer thin films on three types of mono-like cast silicon substrates (flat, upright pyramid and inverted pyramid surfaces) were investigated. Results show that the surface topography structures of the films followed those of the substrates generally. But the thickness of the film on pyramid surface increases from the pyramid tip to the bottom. This is caused by the anisotropical diffusion of incident atoms/ions on the pyramid surfaces during the film growth process. The films on pyramid structured substrates have smaller saturation magnetizations but larger in-plane coercivity than that of on the flat substrate. This should be mainly caused by the non-zero angle between the magnetic field and the substrates as suggested by the angular dependent magnetic properties of the films. The hysteresis loops measured from in-plane to out-of-plane directions show that the coercivities of films on all the mono-like cast silicons are highly angular dependent. A further post-annealing of the films suggests that the magnetic properties of the films are dominantly determined by the surface microstructure of substrates instead of the fabrication conditions. The above results can help better integration of NiFe thin films on mono-like cast silicon based devices. [ABSTRACT FROM AUTHOR]