Search

Tb-Co perpendicular magnetization films are mother materials for perpendicular magnetic recording media. Since the magnetic recording technique is based on magnetic switching of a material, investigating a magnetic the response of the material to a magnetic field is important. The magnetic response of the entire system is the net of each microscopic response of the spin magnetic moment and orbital magnetic moment of the elements. Herein we study the magnetization processes of the spin, orbital, and the element-specific magnetic moments by measuring the magnetic field dependence of the magnetic Compton profile of a Tb12Co88 film. The spin and orbital magnetic moments have opposite orientations. Similarly, Tb and Co magnetic moments have opposite directions. When the total magnetic moment reverses, the orientation of spin and orbital magnetization as well as Tb and Co reverse. Decreasing the temperature, the fluctuation of the magnetic moment of Tb in the perpendicular direction decreases. So the cancelation between the Tb and Co moments reduces total magnetic moment.

We investigated the magnetization process of Fe (110) film using the field dependence of magnetic Compton scattering and M\"ossbauer spectroscopy. From the magnetic Compton profiles, the spin and orbital magnetic moment specific magnetization versus magnetizing field curves were obtained. From the M\"ossbauer spectra, the angles between the magnetizing field and the magnetic moment were obtained. It was found that the magnetizing field dependence of the ratio between orbital moment and spin moment was related to the angles between the magnetizing field and the magnetic moment. We indicate that the magnetic field dependence of the orbital magnetic moment plays a role in the magnetization process., 本研究では磁気コンプトン散乱およびメスバーワー分光を用いてFe薄膜の磁化過程を詳細に調べた。磁気コンプトン散乱からスピン磁気モーメントと軌道磁気モーメントの磁化曲線を算出した。メスバーワースペクトルからは磁化と外部磁場のなす角の印加磁場依存性を調べた。これにより磁化曲線の振る舞いは磁化と外部磁場のなす角の変化と大きなかかわりがあることが分かった。

While the charge transfer between the transition metal and oxygen sites in transition metal oxides has been studied by resonant inelastic soft X-ray scattering, the charge transfer between transition metal sites has not been studied as of yet. In this study, we have measured the Ti 2p edge resonant inelastic X-ray scattering spectra of MTiO3 (M = Mn, Fe, Co, and Ni) in order to investigate the intermetallic M 3d–Ti 3d charge transfer. We found the peak around −4.5 eV in the energy loss scale for all MTiO3, which is attributed to the M 3d–Ti 3d charge transfer; whereas only FeTiO3 exhibits an additional intermetallic charge transfer peak at −2.5 eV. We attributed that the existence of the additional peak in FeTiO3 reflects the relation of M 3d and Ti 3d energy levels.

The charge ordering of Fe 2+ and Fe 3+ ions in LuFe 2 O 4 induces ferroelectricity below 330 K. In this study, the X-ray absorption spectra (XAS) at the Fe L 2,3 -edge are investigated to study charge ordered- and disordered-states. The polarization dependence of XAS revealed that the energy level of ( d xy , d x 2– y 2 ) is lower than that of ( d yz , d zx ). In the charge-ordered state, the Fe L 3 -XAS shows a double-peak structure, which is a characteristic of Fe 2+ and Fe 3+ ions. In the high-temperature region, the double-peak structure becomes a broad single peak, because of overlap with the thermally excited state.

Charge transfer is a key concept in understanding X-ray spectra of transition metal oxides. In this study, X-ray absorption spectra (XAS) and X-ray emission spectra (XES) at the O 1 s -edge of MTiO 3 (ilmenite: M = Mn, Fe, Co, and Ni) have been measured. It was found that the O 1 s -edge XES show the existence of not only oxygen–metal charge transfer but also intermetallic charger transfer. Moreover, the band gap of each ilmenite was evaluated to be 2.4–2.8 eV by measuring the distance between the spectra edges of XAS and XES.

The soft x-ray absorption and magnetic circular dichroism spectra at the Co L2,3-edges of [Co/Pd]20 and [CoB/Pd]20 multilayered films, which were sputter-deposited in Ar gas containing N2 at room temperature, were measured to investigate the electronic and spin states of the films. The macroscopic magnetic properties, such as coercivity and saturation magnetization, and microstructural properties, such as grain size and preferred orientation, were markedly changed for the [Co/Pd]20 film by the B doping and N2 addition. The B doping and/or the addition of N2 gas caused appreciable changes not only in macroscopic magnetic properties but also in microscopic properties, such as the spin angular momentum and orbital angular momentum, throughout the multilayered film. On the other hand, a new spectral feature at the high energy side of the Co L3-edge peak in x-ray absorption spectra was found in only the films with N2 added. Thus, the microscopic properties, such as electronic and spin states, of the Co 3d electronic state for the [Co/Pd]20 and [CoB/Pd]20 films were changed by only the sputtering process with additive N2 gas.

Soft X-ray induced chemical evolution from glycine (Gly) to glycyl–glycine (glycine dimer or Gly–Gly) was studied for sublimated films of Gly. Values of quantum yield of Gly dimer formation were determined by high performance liquid chromatography (HPLC) technique to be: (1.2 ± 0.2) × 10 −1 for 400 eV, (4.6 ± 0.5) × 10 −2 for 407 eV and (3.2 ± 1.5) × 10 −2 for 860 eV irradiation, respectively. We measured X-ray absorption spectra of irradiated Gly films at near edge region of nitrogen K-edge, as a function of X-ray dose. Formation of Gly–Gly was confirmed by the appearance and growth of 402 eV peak, which is a fingerprint of the peptide bond. The important role of surface to chemical evolution is discussed.

The O Kα soft X-ray emission and absorption spectra (XES and XAS) of La 1.2 Sr 1.8 Mn 2 O 7 were measured at selected excitation energies using synchrotron radiation in order to investigate the electronic structure. The dependence of O Kα XES on excitation energy was observed. It is attributed to the 2p partial density of states of inequivalent oxygen sites. It was found that O(1) atom makes Mn 3d 3 z 2 − r 2 orbital stable.

Magnetron-sputtered carbon nitride thin films with different structures and compositions were analyzed by X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), near-edge X-ray absorption ...

An understanding of the microscopic processes underlying the magnetization of the thin films is essential to the design and development of efficient magnetic recording media. In this context, we measure the magnetic Compton profile (MCP) of Tb x Co100−x films (13 x 20) and investigate the microscopic (spin magnetic moment (), orbital magnetic moment (), and element specific magnetic moment ( and )) magnetization processes. Using the magnetic-field dependence of MCP, we obtain the spin- and orbital-specific magnetization curves (SSMH and OSMH, respectively). From the profile-fitting analysis, we also obtain the element specific SSMH curves, and we find from our results that the ratio is nearly constant. Thus, it is assumed that the magnetic switching processes of and cooperatively occur in this system (corresponding to and ). In addition, we observe that and are −1 at x 17. This implies that the magnetic moment of Tb aligns toward the magnetic field in the region of x > 17 and that of Co aligns toward the magnetic field in the region of x < 17. We estimate that this value of x 17 is the compositional point that corresponds to the compensation composition of Tb and Co.

Resonant soft X-ray emission spectra have been measured at the Ni 2p edge of a planar nickel complex K2Ni(CN)4·H2O and interpreted by performing ab initio configuration interaction calculations. This cyano complex shows characteristic metal-to-ligand charge transfer (MLCT) bands in the Ni 2p photoabsorption spectra. Resonant soft X-ray emission via the MLCT intermediate states can be interpreted as valence MLCT excitations within a one-electron picture. On the other hand, resonant soft X-ray emission via the intra-atomic Ni 2p–3d intermediate state corresponding to the white line excitation shows significant electron correlation effects.

The electronic structure of carbon nitride films has been studied using soft X-ray absorption and emission spectroscopy. Resonant N K-emission spectra show a strong dependence on excitation photon energies and the substrate temperatures, while C K-emission band appears insensitive to the different excitation photon energies and the substrate temperatures. Two nitrogen sites are assigned to N bonded to sp 3 -hybridized C and to N bonded to sp 2 -hybridized C.

We propose a new algorithm to achieve a very precise investigation of the three-dimensional atomic nucleus position in a material by the electron holography technique [T. Matsushita, A. Agui, Y. Yoshigoe, Europhys. Lett. 65 (2004) 207]. The algorithm is based on the “scattering pattern matrix” and an iterative gradient method, and it enables three-dimensional atomic-image reconstruction from a single-energy hologram. We measured a single-energy Si(0 0 1) photoelectron hologram of Si 2s emission using an Al Kα light source, and reconstructed the bulk structure with the use of the algorithm. We succeeded in locating as many as 29 atoms. The accuracy of the position for most atoms is within 0.05 nm.

We observed the natural circular dichroism NCD of amino acid films in the soft X-ray region for the first time [M. Tanaka, K. Nakagawa, A. Agui, K. Fujii, A. Yokoya, Physica Scripta, in press]. Based on the success, a new generation of detection system is now under preparation. Vacuum ultraviolet NCD of amino acid films was measured successfully using a polarizing undulator [H. Onuki, Nucl. Instrum. Meth. A 246 (1986) 94] installed at the TERAS electron storage ring at AIST, Tsukuba, Japan. A result of NCD measurement for alanine films is described in detail.

The Ti2p and O1s soft X-ray emission spectra were measured on rutile (TiO2) for the energy region of Ti2p and O1s excitation threshold. The ordinary fluorescence spectra resolve the Ti3d and O2p components in the valence bands. An elastic scattering peak is observed and resonantly enhanced at excitation energies corresponding to Ti2p absorption peaks. Furthermore, an inelastic scattering peak is observed. The peak is assumed to be caused by an elementary excitation that is charge transfer excitation from O2p valence band to Ti3d conduction band.

Soft x-ray emission(SXE) studies of several semiconductors and early transition metal compounds have been carried out. In the case of transition metal compounds, the comparison between photoemission(PES) and SXE spectra shows that the fluorescence spectra are consistent with PES spectra, but the elastic- and inelastic-light scattering spectra reflects the initial 3d states which may be related with the charge transfer state. On the other hand, the inelastic-light(Raman) scattering spectra of semiconductors have been measured in the energy region corresponding to the core exciton states. The Raman scattering spectra whose energy shifts in proportion to the excitation energy are found in the excitation energy region below the absorption edge. It is found that the Raman scattering of semiconductor emits the valence exciton as an elementary excitation.

Soft X-ray emission spectroscopy studies of c-BN have been carried out. We measured B1s- and N1s- SXES and their total yield (TY) spectra. A band gap energy was obtained to be about 6.2 eV. A strong core exciton structure was found in the B1s-TY spectra, but not found in the N1s-TY spectra. The B1s- and N1s-SXES spectra are consistent with the B2p- and N2p-partial density of states (DOS), but the B1s- and N1s-TY spectra are not consistent with the DOS curves of the empty state. As the photon energy varies, the shapes of SXES spectra are changed due to the inelastic-light-scattering effect.

The dynamical mechanism of ferroelectric phase transition in KDP-type crystals has been explained by the order-disorder model of locally distorted PO4 tetrahedrons through fitting of the factorized form of dielectric function including the relaxation mode. From this analysis no soft mode appears but the critical slowing down of the relaxation mode occurs toward to the transition temperature.

The soft x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (MCD) have been measured around the ${M}_{4,5}$ edges at $T=20$ and 300 K in order to investigate the electronic states of ${\mathrm{Eu}}^{3+}$ ions in ${\mathrm{Eu}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$. We found a structure in both the XAS and MCD spectra, which was not observed at $T=20\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, on the lower energy side of the ${M}_{5}$ edge at room temperature. By using atomic model calculations, the origin of the structure is assumed to be due to the thermal effect for the degree of admixture of the excited states ($J=1$, 2) and ground states $(J=0)$ of ${\mathrm{Eu}}^{3+}$. Developing the linear response model to investigate the magnetic moment obtained from the experimental spectra, we conclude that the thermal excited states of ${\mathrm{Eu}}^{3+}$ ions is the linear combination between $J=0$, 1, and 2 and the magnetic-field-excited state is the quantum-mechanically mixed state of the ground and excited states.

Resonant inelastic scattering measurements of the conjugated polymer, poly(pyridine-2,5-diyl) have been performed at the nitrogen and carbon K-edges using synchrotron radiation. For comparison, molecular orbital calculations of the spectra have been carried out with the repeat unit as a model molecule of the polymer chain. The resonant emission spectra show depletion of the π electron bands which is consistent with symmetry selection and momentum conservation rules. The depletion is most obvious in the resonant inelastic scattering spectra of carbon while the nitrogen spectra are dominated by lone pair n orbital emission of σ symmetry and are less excitation energy dependent. By comparing the measurements to calculations an isomeric dependence of the resonant spectra is found giving preference to two of the four possible isomers in the polymer.

Magnetic properties of [Tb20Co80/Pd(0.8 nm)]20 multilayered films with a TbCo layer of thickness 0.2–8.0 nm were studied using spectroscopic techniques of soft x-ray absorption (XAS) and magnetic circular dichroism (MCD) at the Co L2,3 and Tb M4,5 edges. The compensation layer thickness of TbCo, where magnetization becomes zero, was observed to be 5–6 nm. XAS and MCD analyses using the sum rule revealed that the existence of the compensation layer thickness was primarily because the projected Tb 4f magnetic moment was enhanced with the increase in the layer thickness, while the Co 3d moment was independent of the layer thickness. Below the compensation layer thickness, Co sublattice magnetization was dominant.