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Boron-induced electronic states of antiperovskite nitrides such as ferrimagnetic Mn4N were investigated via a combination of polar magneto-optical Kerr effect (p-MOKE) spectroscopy and spectroscopic ellipsometry (SE). The boron content in the Mn4N film varied from 0 to 4.3 at.%, for which the crystal structure was maintained. The amplitude of p-MOKE spectra and the diagonal and off-diagonal dielectric tensors decreased with increasing boron content, which is in agreement with magnetic properties such as magnetic anisotropy and saturation magnetization. These results were related to the lattice expansion and displacement of the charge density in Mn4N by boron doping. However, the peak energy of Lorentz oscillator in the diagonal elements of dielectric tensors suggests that a dominant inter-band transition was independent of boron content.

Spin-charge conversion via spin-orbit interaction is one of the core concepts in the current spintronics research. The efficiency of the interconversion between charge and spin current is estimated based on Berry curvature of Bloch wave function in the linear-response regime. Beyond the linear regime, nonlinear spin-charge conversion in the higher-order electric field terms has recently been demonstrated in noncentrosymmetric materials with nontrivial spin texture in the momentum space. Here, we report the observation of the nonlinear charge-spin conversion in a nominally centrosymmetric oxide material ${\mathrm{SrIrO}}_{3}$ by breaking inversion symmetry at the interface. A large second-order magnetoelectric coefficient is observed at room temperature because of the antisymmetric spin-orbit interaction at the interface of Dirac semimetallic bands, which is subject to the symmetry constraint of the substrates. Our study suggests that nonlinear spin-charge conversion can be induced in many materials with strong spin-orbit interaction at the interface by breaking the local inversion symmetry to give rise to spin splitting in otherwise spin degenerate systems.

We have studied current induced magnetization switching in W/CoFeB/MgO based three terminal magnetic tunnel junctions. The switching driven by spin—orbit torque (SOT) is evaluated in the so-called type-Y structure, in which the magnetic easy-axis of the CoFeB layer lies in the film plane and is orthogonal to the current flow. The effective spin Hall angle estimated from the bias field dependence of critical current (Ic) is ~ 0.07. The field and current dependence of the switching probability are studied. The field and DC current induced switching can be described using a model based on thermally assisted magnetization switching. In contrast, the 50 ns long pulse current dependence of the switching probability shows significant deviation from the model, even if contribution from the field-like torque is included. The deviation is particularly evident when the threshold switching current is larger. These results show that conventional thermally assisted magnetization switching model cannot be used to describe SOT induced switching using short current pulses.

To study how nitrogen contributes to perpendicular magnetocrystalline anisotropy (PMA) in the ferrimagnetic antiperovskite $\mathrm{M}{\mathrm{n}}_{4}\mathrm{N}$, we examined both the fabrication of epitaxial $\mathrm{M}{\mathrm{n}}_{4}\mathrm{N}$ films with various nitrogen contents and first-principles density-functional calculations. Saturation magnetization $({M}_{\mathrm{s}})$ peaks of 110 mT and uniaxial PMA energy densities $({K}_{\mathrm{u}})$ of $0.1\phantom{\rule{0.16em}{0ex}}\mathrm{MJ}/{\mathrm{m}}^{3}$ were obtained for a ${\mathrm{N}}_{2}$ gas flow ratio ($Q$) of \ensuremath{\sim}10% during sputtering deposition, suggesting nearly single-phase crystalline $\ensuremath{\varepsilon}\text{\ensuremath{-}}\mathrm{M}{\mathrm{n}}_{4}\mathrm{N}$. Segregation of \ensuremath{\alpha}-Mn and nitrogen-deficient $\mathrm{M}{\mathrm{n}}_{4}\mathrm{N}$ grains were observed for $Q\ensuremath{\approx}6%$, and were responsible for a decrease in the ${M}_{\mathrm{s}}$ and ${K}_{\mathrm{u}}$. The first-principles calculations revealed that the magnetic structure of $\mathrm{M}{\mathrm{n}}_{4}\mathrm{N}$ showing PMA was ``type B,'' having a collinear structure, whose magnetic moments couple parallel within the $c$ plane and alternating along the $c$ direction. In addition, the ${K}_{\mathrm{u}}$ calculated using $\mathrm{M}{\mathrm{n}}_{32}{\mathrm{N}}_{x}$ supercells showed a strong dependence on nitrogen deficiency, in qualitative agreement with the experimental results. The second-order perturbation analysis of ${K}_{\mathrm{u}}$ with respect to the spin-orbit interaction revealed that not only spin-conserving but also spin-flip processes contribute significantly to the PMA in $\mathrm{M}{\mathrm{n}}_{4}\mathrm{N}$. We also found that both contributions decreased with increasing nitrogen deficiency, resulting in the reduction of ${K}_{\mathrm{u}}$. It was noted that the decrease in the spin-flip contribution occurred at the Mn atoms in face-centered sites. This is one of the specific PMA characteristics we found for antiperovskite-type $\mathrm{M}{\mathrm{n}}_{4}\mathrm{N}$.

Spin-to-charge conversion at metal/oxide interfaces with stacked structures of permalloy/(Cu or Ag)/${\mathrm{Bi}}_{2}{\mathrm{O}}_{3}$ were systematically investigated by using the spin-pumping technique and cross-sectional transmission electron microscopy. Although the transport measurement reproduced the results in previous studies, the interfacial structure of (Cu or Ag)/${\mathrm{Bi}}_{2}{\mathrm{O}}_{3}$ was found to change depending on the crystalline orientation of the Cu or Ag underlayer. While the Ag/${\mathrm{Bi}}_{2}{\mathrm{O}}_{3}$ stacks with Ag(111) had steep interfaces, the formation of a nanometer-scale Cu-O layer can be found in the Cu/${\mathrm{Bi}}_{2}{\mathrm{O}}_{3}$ interface, which should be the main origin of the sign inversion of the conversion coefficients between Cu/${\mathrm{Bi}}_{2}{\mathrm{O}}_{3}$ and Ag/${\mathrm{Bi}}_{2}{\mathrm{O}}_{3}$. This study stresses the importance of nanostructure identification for discussing spin-to-charge conversions at metal/oxide interfaces.

Ferrimagnets are of interest in spintronics owing to the enhancement of spin transfer and spin–orbit torque in the vicinity of the magnetic compensation point. Here, we study the possibility of achieving compensation at room temperature in Mn4−xNixN films grown on SrTiO3(001) substrates by molecular beam epitaxy. The magnetic and magneto-transport properties of 30-nm-thick epitaxial Mn4−xNixN films (x = 0, 0.1, 0.25, and 0.5) were investigated. Ni introduction in Mn4N causes the spontaneous magnetization (MS) to decrease by 45% at x = 0.1 and by 75% at x = 0.25. All samples exhibited the perpendicular magnetic anisotropy required for spintronic applications as well as displaying a sharp magnetization reversal. Remarkably, the sign of the anomalous Hall resistivity changed in the samples between x = 0.1 and 0.25. Further, the magnetization increased for x = 0 and 0.1 and decreased for x = 0.25 when the temperature was decreased. Based on these results, we propose that there is a magnetic compensation composition between x = 0.1 and 0.25, where the magnetization of Mn4−xNixN becomes zero at room temperature. The small MS and perpendicular magnetic anisotropy of the Mn4−xNixN thin films, thus, make them suitable candidates for use in spin transfer torque-based devices.

We investigated the appropriateness of a tunneling magnetoresistance (TMR)-based magnetometer for detecting geomagnetic fields with long-period oscillations through observation of the geomagnetic pulsation (Pi). Pi was not sufficiently observed in the raw outputs due to thermal noise; a bandwidth-limitation treatment helped extract Pi without data stacking. The detectable intensity was reduced to 1 nT with a period of 30 s, but detection was impossible for 100 s. The frequency characteristics revealed that reducing the cutoff frequency of a TMR magnetometer is a promising approach for detecting field oscillations occurring over long periods, such as 100 s.

Ferrimagnetic Mn$_4$N is a promising material for heat flux sensors based on the anomalous Nernst effect (ANE) because of its sizable uniaxial magnetic anisotropy ($K_{\rm u}$) and low saturation magnetization ($M_{\rm s}$). We experimentally and theoretically investigated the ANE and anomalous Hall effect in sputter-deposited Mn$_4$N films. It was revealed that the observed negative anomalous Hall conductivity ($\sigma_{xy}$) could be explained by two different coexisting magnetic structures, that is, a dominant magnetic structure with high $K_{\rm u}$ contaminated by another structure with negligible $K_{\rm u}$ owing to an imperfect degree of order of nitrogen. The observed transverse thermoelectric power ($S_{\rm ANE}$) of $+0.5\, \mu{\rm V/K}$ at $300\, {\rm K}$ gave a transverse thermoelectric coefficient ($\alpha_{xy}$) of $+0.34\, {\rm A/(m \cdot K)}$, which was smaller than the value predicted from first-principles calculation. The interpretation for $\alpha_{xy}$ based on the first-principles calculations led us to conclude that the realization of single magnetic structure with high $K_{\rm u}$ and optimal adjustment of the Fermi level are promising approaches to enhance $S_{\rm ANE}$ in Mn$_4$N through the sign reversal of $\sigma_{xy}$ and the enlargement of $\alpha_{xy}$ up to a theoretical value of $1.77\, {\rm A/(m \cdot K)}$., Comment: 28 pages, 6 figures, 1 table (including supplemental material)

Addition of Co2+ into pristine BaSnO3 (BSO) nanostructures enhanced dye-sensitized solar cell (DSSC) power conversion efficiency (PCE), and the tuned efficiency of 8.22% for 3 at.% of Co doped BSO photoanode with surface treatment and scattering layer, due to the reduction in lattice mismatch and recombination effect. Impedance spectra confirms the DSSC performance by its better photoelectron transport in BSO:Co (483 ohm) compared with pristine photoanode (1202 ohm).

We have studied the transport and structural properties of heterostructures based on a conducting transparent oxide and a ferromagnetic metal $(\mathrm{FM}=\mathrm{Co}$, CoFe, CoFeB) layer. An amorphous indium tungsten oxide (IWO) was used to study possible generation of spin current from a conducting transparent oxide. The resistance of the heterostructure was studied as a function of external magnetic field to evaluate the magnetoresistance (MR) in the $yz$ plane that provides information on the spin Hall magnetoresistance (SMR). We found $yz$-plane magnetoresistance of \ensuremath{\sim}\ensuremath{-}0.2% in IWO/Co and IWO/FeCo heterostructures whereas the effect was nearly zero for IWO/CoFeB bilayers. The MR vanished when a thin (\ensuremath{\sim}1 nm thick) Cu layer was inserted in between the IWO and Co layers. Cross-sectional transmission electron microscopy images and nanobeam diffraction patterns of the films suggested that the Co and FeCo layers formed crystal grains with preferential crystal orientation whereas the Co layer grown on Cu showed grains with random orientation. The CoFeB layer was found to be amorphous. These results show a strong correlation between the crystalline structure of the FM layer and the appearance of $yz$-plane MR, suggesting that FMs with random and/or amorphous structure are suitable for SMR measurements to avoid contamination of the $yz$-plane MR.

The spin-orbit torque (SOT) damping-like (field-like) effective fields and efficiencies, HDL(FL) and ξDL(FL), for the MgO substrate/Fe4N (3 nm)/W (5 nm)/cap metallic heterostructure were determined using harmonic Hall and spin-Hall magnetoresistance (SMR) measurements at various temperatures (T). The resistivity of the W layer was measured to be 40 μΩ cm, suggesting a mixed phase of α and β. The sizable anomalous Nernst component was extracted, and a strong T dependence was found. The resultant ξDL(FL) was estimated to be 0.035 (0.015) at T = 300 K, and 0.045 (0.005) at T = 4 K. The longitudinal MR measurements revealed the negative spin polarization of the conduction electrons in the Fe4N layer. However, no sign reversal of the SOT was observed, as in the case where a CoFeB layer with positive spin polarization was employed. The T dependence of ξDL estimated from SMR measurements was in good agreement with that obtained through harmonic Hall measurements, which was indicative of the sizable spin current injection at the Fe4N/W interfaces due to the spin-Hall effect.

In this study, the exchange coupling properties of submicron patterned Mnlr/CoFe bilayers with strong exchange coupling strength were investigated. The large area of 2.5 mm × 2.5 mm of submicron sized bilayer rings were fabricated by electron beam lithography and ion-milling processes. The clear variations of normalized magnetic hysteresis loops of patterned films are the degradation of pinned CoFe at the Mnlr/CoFe interfaces and the decrease of exchange bias field, comparing with sheet film. After post-field-annealing treatment, only the exchange field was improved. A magnetic tunnel junction ring with outer diameter/linewidth of 2/0.5 μm was constructed as well to further certify the speculations. The magnetoresistance loops of as-fabricated and post-field annealed MTJ ring revealed that the slightly improved magnetoresistance ratio and exchange field. These results were attributed to the rearrangement of distorted spins at the sample edges. However, in comparison with sheet film, the great degradation of magnetoresistance ratio of patterned device, without respect to as-fabricated or post-field annealed, was not retrieved, revealing that the futility of post-field-annealing treatment to the pinning portion of CoFe layer.

The anomalous Hall effect in Fe4− x Mn x N (x = 0, 1, 2, 3, and 4) with antiperovskite structure were investigated. Anomalous Hall conductivity (σAH) strongly depended on the measurement temperature for x = 0 and 4, while constant for x = 1, 2, and 3. σAH decreased with x and even reversed sign for x ≥ 3 at T = 300 K, revealing extremely wide modulation range of σAH. Quantitative analysis based on the existing scaling law suggested that a competition between two components, skew scattering and side-jump, with different polarities is responsible for the x-mediated sign reversal.

Herein, 30 nm-thick Fe4−xMnxN (x = 0, 1, 2, 3, and 4) epitaxial films were grown on MgO(001) substrates by molecular beam epitaxy, and the anisotropic magnetoresistance (AMR) properties were measured at temperatures (T) between 10 and 300 K. A negative AMR effect was observed in the Fe4N and FeMn3N films at T ≤ 300 K and in the Mn4N film at T ≤ 100 K. In contrast, a positive AMR effect was observed in the Fe3MnN and Fe2Mn2N films at T ≤ 300 K. Using the relationship between the AMR ratio, the spin polarization of the density of states at the Fermi level, and the spin polarization of the electrical conductivity (Pσ), we derived the sign of Pσ to be negative in Fe4N, Fe3MnN, and Fe2Mn2N and to be positive in FeMn3N and Mn4N. These results show that the minority spin transport is dominant in Fe4−xMnxN for x = 0, 1, and 2 at lower temperatures, whereas the majority spin transport is dominant with increasing x in Fe4−xMnxN for x = 3 and 4.

Magneto-impedance (MI) of a double-barrier MgO magnetic tunnel junction (DMTJ) is measured as a function of frequency (20 Hz–3 MHz) and DC bias (−1 to 1 V) under magnetic parallel and antiparallel states. A strong nonlinear effect is observed at all frequencies and the MI changes from positive to negative at the relaxation frequency ∼1/RC. A frequency–dc bias ( f – V ) “phase diagram” is mapped out to describe the combination effects of the magneto-impedance response. The decay of the tunnel magneto-resistance (TMR) and tunnel magneto-capacitance (TMC) at high voltage is sufficiently reduced by the double-MgO barrier. The V1 / 2 (the voltage that magnetic response drops to 1/2 of its maximum) of TMC reaches an average value of ∼1.35 V, which is larger than the V1 / 2 of TMR ∼0.95 V, suggesting that the response of TMC is more stable than TMR for high frequency application.

Nanostructured magnetic tunnel junction rings (MTJ) based on CoFeB free layer were fabricated to investigate the corresponding magnetization reversal processes. The dimensions of the MTJ rings were with outer diameter/linewidth of 1 mum/100 nm and 0.7 mu m/100 nm , respectively, in which the fabrication was carried out by a top-down technique in combination with electron beam lithography, ion-milling and etch-back processes. Double transition processes in magnetoresistance (MR) responses are observed in these nanostructured MTJ rings. With considering the surface roughness, an OOMMF simulation was employed to explore the magnetization evolution. The simulated hysteresis loops are consistent with the MR behaviors, unfolding that the magnetic switching process initiates from the forward to reversed onion states through an incomplete vortex state. This two-step switching behavior is reasonably assumed to be due to a pinning site resulting from the surface roughness in a region of the ring. In addition, a series of in situ magnetic force microscopy images extracted from nanostructured MTJ rings reveals the similar magnetization evolution with the simulated results.

The correlation between the magnitudes of spin dependent scattering (ARA) and impurity polarization was examined in current perpendicular to plane (CPP-) giant magnetoresistance (GMR) films with ultra-thin Cu inserted Fe-Co layers, with changing the chemical compositon of Fe-Co. The enhancing effect of ΔRA by Cu insertion was remarkable for Fe 70 Co 30 layers in which the body centered cubic structure is maintained against Cu insertion and large spin polarization of dissolved Cu is observed via X-ray magnetic circular dichroism. We thus conclude that the enhancement of spin dependent scattering originates from the spin polarized Cu atoms embedded in Fe-Co alloys.

It has been widely recognized that Nd-Fe-B sintered permanent magnets are indispensable for highly efficient electromagnetic devices as well as mechanic devices, which are electric motors, tape recorders and undulators at synchrotron radiation facilities [1-5]. On the other hand, due to downsizing of such the devices, the demand for small and multiplex magnets rapidly increases in recent years. To overcome the issues, Nd bonded-magnets are considered one candidate, due to not only the cost efficiency but also the advantages in molding small and multiplex magnets. However, our previous report revealed that the bonded-magnets still have the essential issues that the flux density (B) is much smaller than that for the Nd-Fe-B sintered conventional magnets. Therefore, we have focused on enhancing the B of the bonded-magnets by Halbach-type magnet arrangement [6], and have achieved the improvement up to the B of Nd-Fe-B sintered magnets, which was the target value for our development [7]. However, such the Halbach arrayed magnet involves essential difficulties in the production, so that we investigated the alternative technology to enhance the B by means of magnetizing procedures.

The anomalous Nernst effect (ANE) in highly ordered Fe4N films was examined in the measurement configuration with an in-plane temperature gradient (∇Tx ). The anomalous Nernst coefficient (Q s) in the case of ∇Tx ∥ Fe4N[110] was clearly larger than that in the case of ∇Tx ∥ Fe4N[100]. Note here that no reports on the Q s in Fe4N films have been presented. This anisotropic Q s (Q ani) was also observed in a different configuration with an out-of-plane temperature gradient. Unlike Fe4N, pure Fe and A2-FeAl systems showed a negligible Q ani. This Q ani might be attributed to the specific hybridization effects between the 3d orbitals of Fe and the 2p orbitals of N.

CoFeB/MgO/CoFeB-based magnetic tunnel junctions (CoFeB-MTJs) with the tunneling magnetoresistance (TMR) ratio of 181% and Fe4N/MgO/CoFe-based MTJs (Fe4N-MTJs) with −66% TMR ratio were fabricated using a magnetron sputtering system. In this letter, we report the layout of an electronic circuit comprising both MTJs. Two independent external magnetic fields were applied to the MTJs, which worked as binary inputs as in present logic gates. The demonstrations reveal that the circuits behave like a three-way switching device with NOR logic operation. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A series of tunneling magnetoresistance (TMR) has been measured at various temperatures ranging from 4 K to 360 K for characterizing the electrical transport and magnetization reversal of nanostructured magnetic tunnel junctions (MTJs) with thin effective MgO barrier of 1 nm thickness and resistance-area (RA) product of 10 ??m2. MTJs with 150 250 nm2 elliptical shape were fabricated by using electron beam lithography in combination with ion beam milling. Typical TMR curves were observed at temperature above 70 K, below which there was no significant anti-parallel (AP) state revealed. A linear relationship is found between resistance and temperature in both parallel (P) and AP states, having linear coefficients of -4.15 ×10-4 and -8.07 × 10-4 (?/K), respectively. The TMR ratio was found to be proportional to 1-BT3/2. The negative temperature coefficients and TMR tendency with temperature indicated that electrical transport is dominated mainly by tunneling mechanism. In addition, the biasing field of pinned CoFeB layer due to RKKY coupling increased with decreasing temperature until a maximum biasing field reached at 200 K, after which the biasing field decreased with decreasing temperature.

We report on the magneto-transport measurements of MgO magnetic tunnel junctions (MTJs) composed of NiFeSiB/CoFeB as the free layer for two different structures (top-type and bottom-type pinning). The magneto-transport properties of these MTJs were investigated by varying the thickness of the amorphous NiFeSiB layer for a fixed CoFeB thickness. The tunnel magnetoresistance (TMR), measured in both type of structures, exhibit the same or a higher amplitude (up to 230% measured at room temperature in the case of top-type device), comparing to the case of a single CoFeB free layer. These results suggest that hybrids free layers can be used as good candidates for MTJs with reduced saturation magnetization while keeping a high TMR ratio.

For the MR enhancement in current perpendicular to plane-giant magetoresistance spin valve (CPP-GMR SV), a current-confined path—nano-oxide layer (CCP-NOL)—AlO x was formed on the Cu spacer of half SV structure. In order to form effective current-confining paths, an ultra-thin AlO x layer was deposited on a Cu spacer layer by O 2 reactive sputtering of Al with infra-red (IR) heat treatment on the substrate, and that enable to form an island-structured insulating AlO x layer having holes between AlO x islands. By controlling PO 2 and substrate temperature in the NOL deposition, AlO x layer formation without an oxidizing bottom layer could be achieved.

Controllable remanent states have been studied on the microstructured magnetic tunnel junction (MTJ) rings through magnetoresistance measurements. These rings were designed accordingly with an outer/inner diameter of 2/1 and 1/0.5 mum to reveal two and one metastable states, respectively, during the magnetization reversal process on the free layer. The distinct magnetoresistance levels based on the tunneling magnetoresistance effect are associated with the relative alignment of magnetization of free layer and pinned layer. As a result, four and three controllable remanent magnetic states on the free layer were manipulated by ramping external magnetic fields, applied in the biasing direction, with various field ranges, giving rise to four and three stable magnetoresistance values at zero field. These results may provide a great potential in magnetic multibit memory applications using ring-shaped cells

In this study, current-perpendicular-to-plane great magnetoresistance (CPP-GMR) spin valves with the minimum pillar width of 34 nm phi were successfully fabricated using EB-assisted chemical-vapor-deposition (CVD) hard masks. An area of the obtained magnetic cell is about one order smaller compared with those fabricated with normal EB or photo lithography technique. Measurement of transport properties such as current-induced magnetization switching (CIMS) and MR were demonstrated in such spin valves with various pillar widths. Dependence of the CPP-MR properties on the milled pillar width was discussed. In the case of 66 nm phi width in particular, the MR by external magnetic field switching and CIMS were 0.4% and 0.3%, respectively. The critical switching current Ic was ~40 mA (J c~9times108 A/cm2). In the case of smaller width, only MR by external magnetic field was observed

30-nm scale fabrication of magnetic tunnel junctions (MTJs) was demonstrated. A scanning electron microscope (SEM) was used for chemical-vapor deposition (CVD) of carbon hard masks. Using electron beam (EB)-CVD, less than several 10-nm scale carbon pillar could be formed on MTJ films. Argon ion milling, of which incident angle from the normal of the film plane was determined 45/spl deg/ and 75/spl deg/, was utilized to pattern the MTJs. TMR properties of 80-nm scale MTJs were successfully measured using DC-four-probe at room temperature.

In this study, the output DC electric voltage (V out) generated by a Pt-capped Fe4N bilayer film (Fe4N/Pt) under ferromagnetic resonance conditions at room temperature was assessed. The contributions from the inverse spin-Hall effect (ISHE), the planar-Hall effect (PHE) and the anomalous-Hall effect (AHE) were separated from the output voltage by analysis of V out values determined at varying external field polar angles. The results showed that the polarity of the ISHE (V ISHE) component of V out was opposite to that of the PHE (V PHE). As a result, the magnitude of the intrinsic V ISHE was beyond V out by as much as the magnitude of V PHE. The X-ray diffraction structural analysis revealed the polycrystal of the Fe4N/Pt with (001) orientation, which might be one of the possible mechanisms for enhanced intrinsic V ISHE.

We studied X-ray Fourier transform holography using separated holography-mask and sample geometry. The method was successfully applied to the imaging of the magnetic nanostructure using soft X-ray in addition to the cross-sectional imaging of Cu interconnect lines using hard X-ray.

An instrument for hard X‐ray magnetometry with spatial and time resolutions of 400‐ps and sub‐2‐μm was developed at BL39XU, SPring‐8.The technique is based on X‐ray magnetic circular dichroism measurements combined with KB focusing mirrors and a fast current source, which generates a pulsed magnetic field of 400‐ps duration that is synchronized with the X‐ray pulses provided from the storage ring in the 203‐bunch operation (42 MHz) with a jitter of 50 ps. By fully using the bulk‐sensitivity and element‐specificity of hard X‐ray dichroism, we have demonstrated that the magnetization reversing process in the nanosecond time scale of the free NiFe and pinned CoFeB/CoFe layers were separated in a 10‐μm dot sample with a NiFe/MgO/CoFeB/CoFe/MgO structure mimicking a magnetic tunnel junction device.

The variation of the resonance field and the Gilbert damping parameter (G) with hcp Co film thickness was evaluated by measuring the X- and Q-band ferromagnetic resonance (FMR) for buffer-layer/Co (2–16 nm)/Cu (1 nm)/Pt (15 nm) films. The two types of hcp Co films were deposited at a substrate temperature (Tsub) of either 400 °C or room temperature using a magnetron sputtering system. The G values for the Co films with Tsub = 400 °C exhibited a more rapid increase with decreasing thickness. In addition, the effective linewidth of FMR spectrum exhibited more rapid increase in the Q-band FMR for Tsub = 400 °C. The experimental results suggest that the spin-pumping is enhanced to a greater extent in the Co films fabricated at Tsub = 400 °C. Judging from the structural analysis of the Co films, it is possible that grain growth involving atomically flat surfaces of Co films might enhance the spin-pumping efficiency.

The authors have developed EB assisted chemical-vapor-deposition (CVD) hard mask method. We have reported that by using this method, CPP-GMR spin valves with the minimum pillar size of 34nm could be achieved and a reasonable MR properties were obtained. In this study, CIMS observation was demonstrated in CPP-GMR spin valves with nominal size of 30-80 nm fabricated using EB assisted CVD hard masks. Then we considered size effect on the CIMS phenomena.

The film thickness dependence of the magnetic damping coefficient (α) was investigated by measuring the ferromagnetic resonance (FMR) of Fe4N/NM (NM: Pt and Cu) bilayer films at room temperature. We observed that α in Fe4N/Pt films increased with increasing Fe4N film thickness. Moreover, the enhancement of α, which is represented by the difference in the α values of Fe4N/Pt and Fe4N/Cu films, also increased as the Fe4N film thickness increased. The behavior observed in the Fe4N system was the opposite of that observed for the conventional Ni–Fe system. We speculated two mechanisms occurring in Fe4N/Pt films, which are less magnetic and/or nonmagnetic impurities in the Fe4N films and enhancement of the coercive force (H c) with increasing Fe4N film thickness.