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The effect of high pressure and ion beam irradiation on the magnitude of giant magnetoresistance (GMR) of Fe/Cr magnetic multilayers (MML), [\Fe(20~\ Å )/\Cr(t~\ Å )]20 (abbreviated as \Fe/Cr(t)), has been measured at 77.4 K. It is found that the GMR of Fe/Cr(8) is decreased but that of Fe/Cr(30) is increased by applying pressure. By ion beam irradiation, the electrical resistance of these MMLs is increased significantly and the magnitude of GMR is decreased. Furthermore we have measured the GMR of irradiated Fe/Cr(8) and Fe/Cr(30) under high pressure and compared the results with the sample before irradiation. The GMR of Fe/Cr(8) after the irradiation is found to increase with pressure and the pressure-coefficient of the saturation resistivity is extremely large. These results are discussed on the basis of the spin dependent scattering by the roughness at the interfaces and also bulk scattering in MML in connection with an irradiation-induced instability of the electronic states in Fe/Cr(8). [ABSTRACT FROM PUBLISHER]

Abstract: The amount of residual H in the GaAsN film grown by chemical beam epitaxy (CBE) can be decreased by flow rate modulation growth. Many H atoms in the films grown by CBE exist as N–H or N–H2 structures. Although a higher growth temperature was required for decreasing the H concentration ([H]), it caused a decrease in the N concentration ([N]). A reduction in [H] while keeping [N] constant was necessary. By providing an intermittent supply of Ga source while continuously supplying As and N sources, [H] effectively decreased in comparison with the [H] value in the film grown at the same temperature by conventional CBE without reducing [N]. [Copyright &y& Elsevier]

Abstract: Low-resistivity n-type ZnO thin films were grown by atomic layer deposition (ALD) using diethylzinc (DEZ) and H2O as Zn and O precursors. ZnO thin films were grown on -plane sapphire (- Al2O3) substrates at 300 ∘C. For undoped ZnO thin films, it was found that the intensity of ZnO () reflection peak increased and the electron concentration increased from 6.8×1018 to 1.1×1020 cm−3 with the increase of DEZ flow rate, which indicates the increase of O vacancies () and/or Zn interstitials (Zn i ). Ga-doping was performed under Zn-rich growth conditions using triethylgallium (TEG) as Ga precursor. The resistivity of 8.0×10−4 Ω cm was achieved at the TEG flow rate of 0.24 μmol/min. [Copyright &y& Elsevier]

The magnetoresistance (MR) in Fe/Cr magnetic multilayers (MML) has been measured under high pressure up to 2.5 GPa. It is found that the spin-dependent scattering plays an important role in the pressure dependence of MR ratio. In the present work, for [Fe(20 Å)/Cr(10 Å)]20 MML with antiferromagnetic (AF) state, the pressure coefficient of saturation field Hs is (1/Hs)(∂Hs/∂P) = 3.3 × 10-2 GPa-1 between 0.1 and 2.5 GPa. We found that the (1/∣J∣)(∂∣J∣/∂P) for AF-Fe/Cr MML with polycrystalline structure is opposite in sign to that with epitaxial one. For [Fe(20 Å)/Cr(22 Å)]20 MML with ferromagnetic (F) state, anisotropic magnetoresistance (AMR) decreases with increasing pressure. It is suggested that the anisotropy constant decreases with weakening spin-orbit interaction at high pressure. At high field, the AMR is easily suppressed by applying pressure while the giant magnetoresistance around Hs increases slightly with increasing pressure for polycrystalline Fe/Cr MML. [ABSTRACT FROM AUTHOR]

Thin films of Al–Ni–Co alloy with an average thickness of 15  nm were produced by means of conventional vacuum deposition technique on (0001) sapphire substrates heated at various test temperatures. The microstructures and textures of the films obtained were thoroughly investigated by atomic force microscopy, X-ray diffraction and transmission electron diffraction and imaging techniques. The diffraction measurements have evidenced that the vacuum deposition of Al72Ni15Co13 alloy on the substrates heated above 400°C allows a homogeneous poly-quasicrystalline film, consisting of the Ni-rich basic decagonal phase to grow. It has been further indicated by in-plane XRD analysis that the film deposited at 550°C contains a considerable amount of the decagonal grains epitaxially grown on the sapphire substrate. Possible epitaxial relations occurring between the deposit and the substrate will be detailed on the basis of results obtained from electron diffraction measurements. [ABSTRACT FROM AUTHOR]

Abstract: Faraday rotation spectra of Co/Pt multilayers were obtained in the region including Co M2,3 and Pt N6,7 absorption edges by using multilayer polarizers, and were transformed to magnetic circular dichroism (MCD) spectra by Kramers–Krönig analysis (KKA). From the dependence of the rotation angle on the layer thickness, it was suggested that the magnetization of Co tends to be uniform in Co layers and that of Pt is localized at Co/Pt interfaces. The orbital magnetic moment of Co was estimated to be about 0.17 /Co. The similarity of electronic states around magnetized Pt site between Co/Pt multilayers and CoPt3 alloy is suggested by the resemblance of the MCD spectra of both materials around Pt N6,7 edges. In addition, magnetic Kerr rotation of Co/Cu multilayer was measured and was observed around Co M2,3 and Cu M2,3 absorption edges. [Copyright &y& Elsevier]

La- and V-substituted thin films of Bi4Ti3O12 (Bi3.25,La0.75)(Ti2.97,V0.03)O12 (BLTV) were prepared by metalorganic chemical vapor deposition on (1 1 1)Ir/TiO2/SiO2/Si, (1 1 1)Pt/TiO2/SiO2/Si, and (1 1 1)Pt/Ti/SiO2/Si substrates at 600°C. Film orientation was investigated by X-ray reciprocal space mapping together with the conventional X-ray 2θ–θ scan. All the films consisted of a single phase of BLTV and showed mainly (0 0 1)- and (1 1 7)-orientations on a 2θ–θ scan. However, it was confirmed that the weak (1 1 7)-, strong (1 0 4)-, and (1 1 1)-centered orientations; (1 1 0), (1 1 1), and (1 1 2) orientations, were ascertained for the films deposited on (1 1 1)Pt/TiO2/SiO2/Si, (1 1 1)Pt/Ti/SiO2/Si, and (1 1 1)Ir/TiO2/SiO2/Si substrates, respectively, by the X-ray reciprocal space-mapping measurement. These tendencies were in response to the ferroelectric property of the film. As a result, orientation of the film strongly depended on the kinds of substrates and the X-ray reciprocal space mapping is the useful method to investigate the orientation of the bismuth-layer-structured ferroelectric thin films. [Copyright &y& Elsevier]

Nitrogen ions were implanted into [1 0 0] oriented α-Fe thin films on MgO (1 0 0) substrates at room temperature. The films were annealed at a low temperature of 473 K. α″-Fe16N2 and α′-martensite phases were formed and the volume fractions of these nitride phases were estimated from the X-ray diffraction patterns. When the film thickness was 250 nm, α″-Fe16N2 was formed directly by ion implantation and the maximum volume fraction was about 12%. For the case of 50 nm thick films, no α″-Fe16N2 but α′-martensite was formed after nitrogen-ion implantation, and the volume fraction of the martensite exceeded 90%. By post annealing at 473 K, α″-Fe16N2 was formed, when the implanted specimens were coated with gold or copper films. The volume fraction of α″-Fe16N2 reached about 36%. A SQUID magnetic measurement showed that the saturation magnetization of the nitrogen-implanted 250 nm thick iron films was a few per cent larger than that of unimplanted iron films. [ABSTRACT FROM AUTHOR]

Current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) of the multilayer thin film using a full-Heusler Co2MnSi (CMS) phase as ferromagnetic electrodes has been investigated. A multilayer of Cr buffer (10 nm)/CMS (50 nm)/Cr spacer (3 nm)/CMS (10 nm)/Cr cap (3 nm) was grown on a MgO(100) substrate. The 50 nm thick CMS layer which was deposited on the Cr buffer at 573 K was epitaxially grown and had an L21 structure. The resistance change-area product (ΔRA) at room temperature was 19 mΩ μm2, which is one order of magnitude larger than those in previously reported trilayer systems, resulting in the MR ratio of 2.4%. A possible origin of the enhanced ΔRA is considered to be the large spin polarization in a high-quality L21 CMS film. [ABSTRACT FROM AUTHOR]

Spin Seebeck effect (SSE) was investigated in Heusler compound Co2MnSi (CMS) and ferromagnetic binary alloy Ni80Fe20 (Py) thin films deposited on MgO substrates at different ambient temperatures, T = 30 K to 295 K, by maintaining a finite temperature gradient along the film plane. Low temperature enhancement of voltage signal and a peak around T = 70 K were detected in a Pt wire placed on the higher temperature end of CMS (or Py) film. It has been found that the low temperature enhancement was dominated by a thermal artifact, which was generated by the anomalous Nernst effect with an additional perpendicular temperature gradient across the film plane. The remarkable mismatch between thermal conductivities of MgO and CMS (or Py) at low temperatures is considered to give rise to the perpendicular temperature gradient causing the thermal artifact. We showed that consideration of thermal conductivity matching between thin film and substrate is essential for performing experiments of SSE correctly; moreover, the observation of SSE could be realized only when minimization of the thermal artifact is possible. [ABSTRACT FROM AUTHOR]

Interlayer exchange coupling (IEC) was studied in ferromagnetic binary alloy Co-Fe thin films through Cr spacer to investigate systematically, the effects of chemical compositions and the chemical ordering on the observation of 90° interlayer coupling in magnetic alloy based structures. The dominating 180° coupling with weak 90° coupling was observed at room temperature deposited CoxFe1-x/Cr/CoxFe1-x (x=0 to 0.8) trilayer samples for all values of x. However, the strength of the 90° coupling for x=0.4 and 0.5 was found to increase with increasing the annealing temperature, Tann for the bottom CoxFe1-x layer and the strength of 90° coupling became comparable to that of 180° coupling at Tann=400 °C. The enhancement of 90° coupling was considered to be originated from the unconventional interfacial magnetic exchange interactions between Cr and Co (and Fe) due to the appearance of antiphase structures at the interface with the enhancement of chemical ordering (B2 ordering) which was confirmed by synchrotron X-ray diffraction. [ABSTRACT FROM AUTHOR]

The recently discovered spin Seebeck effect (SSE) which generates spin voltage due to a temperature gradient in ferromagnets, was systematically studied in half-metallic Heusler compound Co2MnSi (CMS)/Pt thin films to investigate the effect of spin polarization of ferromagnetic layer on SSE. An epitaxial thin film of CMS with an almost perfect B2-ordered structure was prepared directly on a MgO(001) substrate. The measurement was performed at room temperature for various temperature differences, ΔT = 0-20 K between higher (300 K+ΔT) and lower (300 K) temperature ends along the film. The clear sign reversal of the thermally induced spin voltage due to SSE at the higher and lower temperature ends of the CMS film was detected by means of inverse spin-Hall effect in a Pt wire. The SSE was also investigated in a Py thin film deposited on a MgO(001) substrate and compared to that with CMS to verify the effect of spin polarization on SSE. Comparable signals of SSE in CMS and Py thin films suggested that thermal excitation of magnons might have more vital effects in SSE than the degree of spin polarization in ferromagnetic metals. [ABSTRACT FROM AUTHOR]

Abstract: SrIrO3 films were grown on (111)SrTiO3 substrates at 650 to 700 °C by metal organic chemical vapor deposition (MOCVD). Stoichiometric films were obtained above 650 °C for a wide range of input gas flow rate of Ir source under a fixed rate for a Sr source. (001) m -oriented monoclinic SrIrO3 films with in-plane 3-varian were epitaxially grown and their rocking curve full width at half maximum (FWHM) of (001) m peaks were forward to be narrow, i.e. 0.075°. Average surface roughness (Ra) of such film was 0.30 nm, which suggests that the surface is smooth. Resistivity at room temperature was about 1300 μΩ cm and (111)-oriented epitaxial Pb(Zr0.4Ti0.6)O3 films with smooth surfaces were successfully grown on these SrIrO3 films. Good ferroelectricity characteristics comparable to those on (111) c SrRuO3 O3 was obtained except for the large coercive field (E c) values. [Copyright &y& Elsevier]