小泉 昭久

With the breakdown of coherent Kondo scattering with rising temperature, the Fermi surface (FS) in rare-earth Kondo lattices is expected to transition from the large FS counting the 4f moments, which form entangled quasiparticles with strongly enhanced effective masses with the conduction states, to the small FS with decoupled and localized 4f moments. A direct observation of this transition with temperature has, however, remained elusive, because conventional probes of the FS in Kondo lattices require high magnetic fields, which might reconstruct the FS or cannot work reliably at elevated temperatures. Using high-resolution Compton scattering, we overcome these limitations and show that the FS topology in the prototypical Kondo lattice YbRh2Si2 undergoes pronounced changes between 14 and 300 K in zero magnetic field. In particular, we present clear evidence for a largely restored small FS at room temperature. Our results suggest the relevant energy scale of the complex Kondo crossover phenomenon in YbRh2Si2.

We have measured directional Compton profiles on the (0001) plane in the UPd2Al3 single crystal with hexagonal symmetry in order to investigate the change in electronic structure related to the crossover phenomenon between the itinerant and localized states of 5 f electrons. Two-dimensional electron occupation number densities (2D-EONDs), which are the projection of Fermi volumes on the view plane, are obtained at 20 and 100 K through electron momentum reconstruction and Lock–Crisp–West folding analysis. We have also derived theoretical 2D-EONDs from the results of band calculations with the linear muffin-tin orbital method for comparison. The experimental 2D-EONDs at 20 and 100 K are well described by the theoretical ones based on the itinerant and localized models of 5 f electrons, respectively. Therefore, the contributions of 5 f electrons to the Fermi surfaces in the itinerant state are verified around Γ (A) points in the first Brillouin zone through comparison.

We have measured directional Compton profiles on the (001) plane in URu2Si2 single crystal at several temperatures. Two-dimensional electron occupation number densities (2D-EONDs) were obtained from the profiles through electron momentum reconstruction and Lock–Crisp–West folding analyses. We have also performed band calculations based on 5 f-electron itinerant and localized models and derived theoretical 2D-EONDs for comparison. The experimental 2D-EOND at 300 K is well described by the localized model, and the 2D-EOND at 10 K is consistent with the theoretical one based on the itinerant model. The difference between 2D-EONDs at 30 and 100 K reflects a gradual change in the electronic structure, which reveals some of the crossover phenomena from localized to itinerant states. The change from localized to itinerant states is also reflected in a B(r) function, which is obtained in the reconstruction analysis and is an autocorrelation function of the wave function in the position space. The process by which the electronic structure in URu2Si2 changes is demonstrated through a series of experimental results.

A cryostat was constructed for high-resolution X-ray Compton scattering measurements at temperature down to 1.7 K, in order to investigate superfluid helium-4. Compton profiles of helium were measured using synchrotron X-rays for gas and liquid phases, respectively. In the measurement of the liquid phase, we succeeded in measuring the Compton profile of the superfluid helium at 1.7 K. Comparison of the results with theoretical calculation reveals importance of many-body effects beyond the mean-field treatment of electron systems.

We report the change of electronic structure associated with the hidden-order (HO) transition in URu2Si2 through Compton scattering experiment on the (001) plane of the single crystal. The two-dimensional electron occupation number densities (EONDs) obtained at 14 and 20 K, which are the projection of Fermi volume onto the kx-ky plane of the first Brillouin zone, clearly reflect a whole image of electronic structure in the HO and paramagnetic (PM) phases, respectively. The change in electronic structure is well described by theoretical EONDs derived from the result of a band calculation, where U5f electrons are treated as itinerant ones. We also evaluate the electron (hole) numbers in the HO and PM phases and, therefore, its change on the HO transition. The HO transition is deeply involved with a significant change in 5f electrons from partially localized to itinerant states through hybridization with conduction electrons, resulting in the reconstruction of Fermi-surface structure.

The magnetic Compton scattering of a Tb32Fe55O 13 film was measured in order to investigate the microscopic magnetization processes (i.e., the spin moment, orbital moment, and element specific moments). The trend of the spin magnetic moment was the same as that of the total magnetic moment but opposite to the orbital magnetic moment. In the low magnetic field region, the magnetic moments were not perfectly aligned perpendicular to the film surface, and the perpendicular components were found to mainly arise from the magnetic moment of Tb. Oxygen atoms hinder long range magnetic interaction and hence also affect the magnetization process of the magnetic moments of Tb and Fe. © 2013 AIP Publishing LLC.

We present an application of magnetic Compton scattering (MCS) to decompose a total magnetization loop into spin and orbital magnetization contributions. A spin magnetization loop of SmAl2 was measured by recording the intensity of magnetic Compton scattering as a function of applied magnetic field. Comparing the spin magnetization loop with the total magnetization one measured by a vibrating sample magnetometer, the orbital magnetization loop was obtained. The data display an anti-coupled behavior between the spin and orbital magnetizations and confirm that the orbital part dominates the magnetization. © 2013 American Institute of Physics.

High resolution Compton profiles have been measured in the single crystal of CeRu2Si2 above and below the Kondo temperature to elucidate the change of the Ce-4f electron from localized to itinerant states. Two-dimensional electron occupation number densities projected on the first Brillouin zone, which are obtained after a series of analyses, clearly specify the difference between itinerant and localized states. The contribution of Ce-4f electrons to the electronic structure is discussed by contrast with a band calculation. © 2011 American Physical Society.

First and second order magnetic transitions in Ce (Fe0.97Ir 0.3)2 are studied using the magnetic Compton scattering technique. The measurements on polycrystalline sample were carried out at SPring8, Japan for different temperatures and magnetizing fields using 175 keV elliptically polarized synchrotron radiation. The temperature dependent magnetic effects (ratio between magnetic scattering intensity and charge scattering intensity) show the magnetic transitions from antiferromagnetic→ ferromagnetic→paramagnetic phases which are consistent with the magnetization data. The temperature and field dependent spin-polarized momentum densities have been analyzed mainly in terms of contribution from Fe (3d) and Ce (4f) sites to determine their role in the formation of total spin moments and thereby magnetic transitions. © 2010 American Institute of Physics.

Magnetic Compton profiles (MCPs) of Co/Pt multilayers have been measured from a view point of perpendicular magnetic anisotropy (PMA). The PMA and the MCPs are discussed in the present Co/Pt results together with the previous Co/Pd results. The anisotropies of the MCPs have been decomposed into each magnetic quantum number |m| =0, 1, and 2. The decomposition analysis has suggested that the |m| =1 state contributes to the PMA when the multilayer films change in-plane magnetic anisotropy to the PMA, and that the |m| =2 state contributes to the PMA when the multilayer films have large PMA energy. © 2010 American Institute of Physics.

We have studied the [100]-[110] anisotropy of the Compton profile in the bilayer manganite. Quantitative agreement is found between theory and experiment with respect to the anisotropy in the two metallic phases (i.e., the low temperature ferromagnetic and the colossal magnetoresistant phase under a magnetic field of 7 T). Robust signatures of the metal-insulator transition are identified in the momentum density for the paramagnetic phase above the Curie temperature. We interpret our results as providing direct evidence for the transition from the metalliclike to the admixed ionic-covalent bonding accompanying the magnetic transition. The number of electrons involved in this phase transition is estimated. Our study demonstrates the sensitivity of the Compton scattering technique for identifying the number and type of electrons involved in the metal-insulator transition. © 2009 The American Physical Society.

Orbital ordering state of 3d electrons in YTiO3 has been studied by magnetic Compton profile (MCP) measurement for crystallographic directions of [100] (a-axis) and [001] (c-axis). The magnetic effect of the observed MCP leads to the spin moment that is equal to the saturated magnetic moment within the estimated errors, which strongly suggests quenching of the orbital moment. Shape of the observed MCPs shows directional anisotropy between the two axes. The MCPs are calculated by using an atomic model wave function of a linear combination of two 3d-t2g orbitals, udyz ± vd zx (u2 + v2 = 1) for the Ti sites. The observed MCP is best reproduced by the calculated MCP with u = 0.84 ± 0.04 and v = 0.54 ± 0.04. This value of u is slightly larger than those obtained in the previous studies. ©2008 The Physical Society of Japan.

The electron momentum densities of the layered transition metal trichalcogenide ZrTe 3 have been studied by high-resolution Compton profiles (CPs) along the a*, b*, and c* directions, together with the theoretical CPs calculated using the local-density approximation based full-potential linearized augmented plane wave method. A fairly good accord between theory and experiment is found with respect to the overall shapes of the CPs and the anisotropies in the CPs defined as differences between pairs of various CPs. The observed anisotropy between b* and c* directions is much smaller compared with the others, in agreement with the theoretical result. It is shown that the Fermi surface geometry plays an effective role to reproduce the anisotropies. The characteristics of the Fermi surfces and bonding conditions in the ZrTe 3 are examined, and insights of the features in the CPs are gained. ©2007 The Physical Society of Japan.

Local chemical bonding and magnetic Compton profiles were used to study the origination of perpendicular magnetic anisotropy (PMA) in amorphous TbFeCo films. Experimental results suggested oxygen atoms can change the local chemical bonding. Anisotropic chemical bonding of Fe3d and Tb4f electrons are found for films with suitable oxygen composition. It is concluded that the origination of PMA in amorphous TbFeCo films is related to the composition of oxygen atoms in the films. © 2006 Elsevier B.V. All rights reserved.

Anisotropies of spin densities in momentum space are obtained on Pt/Fe multilayers by magnetic Compton profile (MCP) measurements. The contribution of the spin densities are separated into Fe layer contribution and Pt layer contribution. From the separation analysis, it is concluded that the perpendicular anisotropy of a Pt/Fe multilayer is dominated by the Fe 3d electrons. © 2006 Elsevier B.V. All rights reserved.

Magnetic Compton profiles (MCPs) of TbFeCo amorphous films have been measured from a viewpoint of perpendicular magnetic anisotropy (PMA). Analysis of anisotropies of the MCPs has shown that anisotropies of wave functions are small in both a PMA film and an isotropic magnetization (IM) film. Element selective analysis of the MCPs has shown that a Tb magnetic moment and a magnetic moment of 3d transition metal (TM) are coupled antiparallel in the PMA film. In the case the IM film, the magnetic moment of 3d TM tends to align toward the magnetic field but the Tb magnetic moment distributed to random orientations. The PMA natures reflect the magnetic structures of the Tb magnetic moment and the 3d TM magnetic moment in the TbFeCo films. © 2007 American Institute of Physics.

Anisotropies of spin-projected wave functions are measured on a PdCo multilayer system by measuring magnetic Compton profiles. The anisotropies of the wave functions are decomposed into the contributions of Co 3d states and Pd 4d states using an atomic model by a Hartree-Fock calculation assuming uniaxial (cylindrical) symmetry. Perpendicular anisotropy in PdCo multilayers is dominated by the anisotropy of Co 3d states; states with both magnetic quantum number ∫m∫ =2 and ∫m∫ =1 contribute. © 2006 American Institute of Physics.

We have measured directional magnetic Compton profiles between [100] and [110] directions in a bilayer manganite at 10 K. The two-dimensional spin momentum distribution of the Mn 3d state is reconstructed from them. The result is examined in both terms of molecular orbital and band schemes. The eg type orbitals are dominated by the x2 - y2 type orbital. The occupation-number density in the k space obtained by the Lock-Crisp-West folding is not explained only by the band picture, and suggests that a polaronic state of eg type electrons coexists in the ferromagnetic metal phase below Tc. © 2006 The American Physical Society.

Magnetic Compton profiles (MCP) have been measured in the [100], [110] and [001] directions on the single crystals of La2-2xSr 1+2xMn2O7 (x=0.30, 0.35 and 0.42) at 10 K. The occupation numbers in t2g and two eg type orbitals (x 2-y2 and 3z2-r2) of Mn-3d state are evaluated from the line-shape analysis of MCP's in the [001] direction by using theoretical profiles derived from the ab initio calculations for (MnO 6)8-cluster. It has been found that the eg state is dominated by the x2-y2 type orbital at every hole concentration, x, and the 3z2-r2 type orbital population decreases with increasing x. From the result, the connections of eg orbital state with the electron correlation effect, exchange interactions, lattice distortion and electronic inhomogeneity are discussed. © 2005 Elsevier Ltd. All rights reserved.

We report on the study of spin moments in Ce(Fe0.94Ru0.06)2 using magnetic Compton scattering. The measurements on polycrystalline sample were carried out at SPring-8, Japan with 175 keV elliptically polarized synchrotron radiation at 70, 90, 120, 150, and 190 K in 2 T field. The temperature variation of the magnetic effect exhibits clearly the double magnetic transition, i.e., from antiferromagnetic to ferromagnetic and ferromagnetic to paramagnetic transition in agreement with the resistivity and magnetization studies on this material. A comparison of temperature-dependent spin moments in the present sample with Ce(Fe0.96Ru0.04)2 shows interesting features of spin momentum density. © 2005 The American Physical Society.

Interlayer magnetic coupling (IMC) between Fe and Gd layers through Al spacer has been experimentally studied on [Al(R Å)/Gd(40 Å)/Al(R Å)/Fe(20 Å)]xN/Al(5 Å) magnetic multilayers, where R = 0, 5, 10, and 20 as nominal figures. Magnetization curves and the temperature dependence of magnetization are reported. Magnetic Compton-profile technique has been used to determine the amounts and the signs of spin magnetizations of Fe and Gd layers for R = 5 and 20. A line-shape analysis of the magnetic Compton profile on the multilayer of R = 5 has verified that the IMC is antiferromagnetic, and the negative small amount of magnetization of Gd layer exists even at room temperature under 1 kOe, despite the absence of ferromagnetic magnetization of a Al(5 Å)/Gd(40 Å) multilayer at room temperature. The antiferromagnetic IMC has been confirmed in the case of R = 0, 5 and 10, but the IMC is not observed in the case of R = 20. ©2005 The Physical Society of Japan.

The spin-polarized electron momentum distribution (magnetic Compton profile: MCP) of ferromagnetic Sr2FeMoO6 has been measured using the magnetic Compton scattering technique at room temperature. The experimental MCP is in good agreement with that obtained by a first-principles band-structure calculation. The experiment and calculation reveal a hollow around pz = 0, which support the conclusion that there exists a negatively spin-polarized Fe 3d-Mo 4d mixed state.

The spin-polarized electron momentum distribution [magnetic Compton profile (MCP)] of ferromagnetic Sr2FeMoO6 has been measured, using the magnetic Compton scattering technique, at temperatures 10 K and 300 K, for the [100] and [110] crystallographic directions. The experimental results have been compared with results from electronic structure calculations performed utilizing the full potential linearized augmented plane-wave method. The calculated results clearly show that only down-spin states contribute to the EF intensity (half metallic character). The experimental observations clearly show evidence for the existence of negative spin polarization that arises from down-spin bands. We have observed the change in the MCP, which arises from the band spin fluctuation, between the low temperature 10 K and high temperature 300 K.

A magnetic Compton profile of SrRuO3 has been measured to elucidate the Ru-O orbital hybridization and orbital occupation. The obtained profile is compared with results of a molecular orbital Hartree Fock calculation based on a (RuO6)8- cluster. The spin polarization of strongly hybridized Ru t2g-O p orbitals are observed on the magnetic Compton profile. Furthermore, the partial occupation of Ru eg-O p orbitals, discussed by previous band theory studies, is shown to be very small.

Temperature dependence of magnetic Compton profile (MCP) has been measured on a single crystal of La2-2xSr1+2xMn2O7 at x=0.42 along the c-axis. The spin magnetic moments of Mn 3d electrons in t2g and eg type orbitals are evaluated from the line-shape fitting analysis of MCP’s using theoretical profiles derived from the (MnO6)8- ab initio calculations. The experimental ratios of eg spins to t2g ones show higher values above the metal-insulator transition temperature Tc in comparison with the value expected from the electronically homogeneous state. This is understood in terms of the phase separation between electron-rich ferromagnetic and electron-poor antiferromagnetic regions. The ratios indicate that the eg electrons are highly segregated in the ferromagnetic region. In addition, the fitting result just above Tc suggests that the eg-orbital state involved with the colossal magnetoresistance effect is optimized by an external magnetic field. © 2004 The American Physical Society.

Investigation of the magnetic moment of nickel in the polycrystal GdNi2 Laves phase was carried out by means of magnetic circular dichroism (MCD) in the core-level x-ray-absorption spectroscopy. It was revealed that the nickel magnetic moment originating from the 3d state (band) does exist and couples antiparallel to that of gadolinium whose MCD was observed at the M4,5 absorption edge. That is, nickel retains an intrinsic magnetic moment even in the Laves phase concentration. Furthermore, by analyzing in terms of sum rule, the contribution of spin and orbital magnetic moments to the magnetic moment was evaluated and discussed.

Experimental and theoretical directional magnetic Compton profiles (MCP's) of hcp-Co, fcc-Fe50Ni50 and fcc-Ni are compared with each other to elucidate the difference of the electronic structures of magnetic electrons between fcc-Fe50Ni50 (almost equivalent to fcc-Co) and hcp-Co, and between fcc-Fe50Ni50 and fcc-Ni. Small difference is found experimentally in the former case along the corresponding crystalline axes in a region pz < 2 au. The difference is isotropic in shape between these crystals, which can be ascribed to the difference of the spin polarization of mainly s-like electron. In the later case, the experimental main difference is theoretically explained with the d-like 4-th and the d-like 5-th band MCP's. Anisotropies of the MCP in Co are experimentally confirmed for the first time. Limitation of the theoretical calculation based on the single particle approximation is suggested. © 2003 The Physical Society of Japan.

Element-specific magnetic field hysteresis on a Fe(20Angstrom)/[Gd(30Angstrom)/Fe(20Angstrom)] x 50 multilayer has been measured by means of X-ray magnetic circular dichroism at Gd-L-3 and Fe-K edges at 16 K, 195 K and 300 K, together with bulk magnetization measurements. These results are examined on the basis of Camley's model, which describes the multilayer as a one-dimensional spin chain. At 195 K, which is near the compensation temperature, the observed hysteresis curve is interpreted as a series of magnetic states: canted Fe-aligned, surface-twisted, and Fe-dominant bulk-twisted states. These unique spin configurations are promoted by the surface magnetization of outermost Fe slabs and the exchange-springlike behavior within Gd slabs.

The spin moments in a Ce(Fe0.96Ru0.04) 2 sample at 20, 50, 70, 150, and 190 K have been determined from magnetic Compton scattering experiments. The measurements on polycrystalline samples were carried out on beam line BLO8W at super photon ring 8 GeV (SPring-8), Japan with 274.46-keV elliptically polarized synchrotron radiations. It is seen that the variation of magnetic effect (deduced from the ratio of the magnetic to charge intensities) is consistent with the antiferromagnetic and paramagnetic transitions, as seen in resistivity and magnetization studies. The data is analyzed for temperature-dependent spin moment contributions from different magnetic electrons of Ru-doped CeFe2.

From the magnetic Compton-profile (MCP) measurement, we have directly differentiated for the first time the populations in two e(g)-type orbitals (x(2) - y(2) and 3z(2) - r(2)) in a manganite. The experimental MCP's along the [001] direction for La2-2xSr1+2xMn2O7 at x = 0.35 and 0.42 are fitted by the theoretical profiles obtained from the (MnO6)(8-) ab initio calculations. The calculation confirms that the MCP clearly detects the oxygen hybridization in the e, orbitals. The e, state: is dominated by the x(2) - y(2)-type orbital with almost constant population, while the population in the 3z(2) - r(2)-type orbital decreases with increasing the hole concentration x.

Magnetic Compton profiles (MCPs) of a DyCo5.4 single crystal were measured at 10 K, 200 K and 300 K. The temperature dependence of the spin moment, which is deduced from the areas under the normalized MCPs, is significantly different from that of the total magnetization measured by a superconducting quantum interference device (SQUID). This difference is due to the presence of a substantial amount of the orbital moment on a Dy site that does not contribute to the magnetic Compton scattering cross section. The analysis of the MCPs reveals that the absolute value of the spin moment increases with increasing temperature and that the spin magnetic moment of the conduction electrons has an opposite sign to the total spin magnetization in the covered range of temperature.

Noticeable enhancement of the spin-dependent Compton scattering intensity in right-angle scattering has been achieved by using high-energy X-rays having elliptical polarization. A promising momentum resolution of better than 0.4 atomic units for Compton-profile measurements is firmly predicted by means of an ordinary Ge solid-state detector when the scattering-angle divergence at 90° is crucially restricted. It is pointed out that the angle between a scattering vector and the direction of sample magnetization can be chosen as 90° without seriously weakening the spin-dependent effect. Comparison is made between 274 keV and 122 keV experiments.

Element-specific magnetic hysteresis in a Gd/Fe multilayer has been obtained at the Gd L-3 and the Fe K edges by means of x-ray magnetic circular dichroism (XMCD) measurement with a helicity-modulation technique. Both hysteresis curves at 20 K show characteristic sharp peaks at the coercive field H-c = +/- 50 Oe. Above H-c, the intensities of XMCD gradually decrease with increasing magnetic fields, whereas the bulk magnetization monotonously increases. These results are explained by the theoretical prediction by Camley and co-workers.

Two monochromators for high-energy synchrotron radiation have been studied at the elliptical multipole wiggler beamline BL08W of SPring-8. Both monochromator crystals are bent and indirectly water-cooled. In the 100 keV monochromator an efficient cooling scheme is employed. A monochromatic beam is successfully focused using new benders for the 100keV and 300 keV monochromators. Measured radii of curvature of the bent crystal agree qualitatively with calculation.

Hysteresis loops of amorphous Tb60Fe20Al20 are measured at several sweep rates of a magnetic field at 4.2 K. At a fast sweep rate of 0.25 T/s, magnetization abruptly jumps at 2.9 T, while the jump disappears at a slow sweep rate of 0.004 T/s. The magnetization jump is considered to reflect the dissipation mechanism of spin-reversal energy in adiabatic system. © 1998 Elsevier Science B.V. All rights reserved.

A pulse magnet is applied to an experiment on magnetic Compton scattering using circularly polarized synchrotron-radiation X-rays. The sample is c-axis oriented SmCo5, which is known to be a hard magnetic materials. Consecutive pulsed magnetic fields of 11.7 tesla are used to repeatedly reversed the magnetization direction of the sample. The measurement is done with residual magnetization of the sample at room temperature. The magnetic Compton profile is found to be well-reproduced by a combination of a theoritical Sm-4f profile and an experimental Co profile. On the assumption that the Co spin moment in the haxagonal symmetry is 1.6μB; the Sm-4f spin moment is evaluated to be -1.79μB which is quite small compared with the expected spin moment 3.57μB for the Sm ground state (J = 5/2 MJ = 5/2). This experiment suggests for the first time the feasibility of using pulse magnets for X-ray magnetic scattering and absorption measurements on hard magnetic materials.

The magnetic moment of (Formula presented) in hcp Sm was studied with a magnetic Compton-scattering experiment with the aid of a pulse magnet. We have successfully obtained direct evidence for a positive contribution of the spin moment to the total moment, opposite to the case for a free ion. The enhancement of the spin moment by incorporation of the conduction electron polarization is observed. © 1997 The American Physical Society.

A measurement of the magnetic form factor of a ferromagnetic actinide compound of UTe with circularly polarized X-rays is reported. The present geometrical configuration of the measurement gives a form factor of L(k) + 0.3 S (k) where L(k) and S(k) are the form factors of the orbital and the spin magnetic moment, respectively. We have combined the X-ray magnetic form factor with the neutron one which gives L(k) + 2S(k) (G. Busch et al.: J. Phys. c 12 (1979) 1391), and have deduced L(k) and S(k) separately. The obtained profiles of L(k) and S(k) show that the orbital and the spin magnetic moments are spatially spread out more than those calculated for a free uranium ion. © 1995, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

Directional magnetic Compton profiles (MCPs) of ferromagnetic intermetallic compound Mnj.1Sb are measured using a circularly polarized synchrotron radiation light source. The overall shape of the derived momentum-density distribution of the magnetic electrons is reproduced well with the Hartree-Fock 3d wavefunction of free Mn atoms except in the low momentum region (IPI 2.0 atomic units). The anisotropy observed in the low momentum region is inexplicable only with the population, determined previously by a polarized neutron measurement, of unpaired electrons in Mn-3d orbitals in the trigonal crystalline field. The present result suggests an additional anisotropic negative polarization of Sb-5p electrons. The anisotropy is discussed using the hydrogen-like atomic Sb-5p wavefunctions. © 1995, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

The temperature dependence of circularly magnetic x-ray dichroism (CMXD) spectra at the Fe K-edge has been measured in a Fe73.4Ni26.4 alloy. The CMXD signal intensities at the Fe K-edge are proportional to the total magnetization of the alloy. (c) 1993 The Japan Society of Applied Physics. © 1993 The Japan Society of Applied Physics.

X-ray magnetic circular dichroism and X-ray absorption near-edge structure have been measured at the Pt L2 g-edges of Fe-Pt alloys in ordered and disordered phases. The intensity ratio between these spectra at the L2- and Z/g-edges substantially deviates from the predicted values, which indicating that orbital angular momentum exists on the unoccupied 5d-states of Pt atom. The orbital angular momentum calculated by new magneto-optical sum rule is compared with the results of band calculation. © 1993 The Japan Society of Applied Physics.

The first systematic measurements of circular magnetic X-ray dichroism (CMXD) effects at the K-edge in 3d-transition metal alloys have been made in Fe-Ni alloy over a wide composition range. It has been found that the CMXD spectrum at the Fe K-edge is similar to that at the Ni K-edge in each alloy, indicating that the CMXD spectra at the K-edge mainly reflect an itinerant character of 4p-states. The features of the CMXD spectra correspond to those of X-ray absorption near-edge structure (XANES) spectra, reflecting the change of crystal structure. The signal intensities around the absorption edge energy, E0, have strong Ni concentration dependence, suggesting a close relationship between the CMXD effects around Eq and the spin polarization of 3d-states. © 1993, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

The X-ray resonance exchange scattering (XRES) has been measured at the Nd L23-edges on the 330, 440 and 550 Bragg reflections in a ferromagnetic Nd2Fe14B single crystal. The XRES results at the L2-edge reflect the spin polarization of unoccupied 5^-bands of Nd due to electric dipole transitions. Those at the L3-edge show the possibility of electric quadrupole transitions to the highly localized 4/-states. The temperature dependence of XRES confirms the sensitivity to the local magnetic moment of specific site. The magnetic moments of Nd 4/and 4g sites rotate from the c-axis with different angles below spin reorientation temperature. © 1993 The Japan Society of Applied Physics.

Angle-dependent X-ray magnetic circular dichroism has been measured to make clear quadrupolar contribution to the dichroic spectrum at the Ho L2, 3-edges in holmium-iron-garnet. A distinction between dipolar and quadrupolar contributions is made on the basis of the recently developed theory. The experimental result is not consistent with the theoretical predictions. © 1993 The Japan Society of Applied Physics.

Magnetic X-ray absorption near the edge structure (magnetic XANES) as a new technique is applied to ordered and disordered FePt alloys in order to study the magnetic local environment effect. From the magnetic XANES at the Fe K-edge, it is suggested that the 3d-electronic states of Fe are sensitively influenced by the local environment depending on concentration and/or symmetry. The magnitude of the magnetic XANES at the Pt L2,3-edges is not directly corresponding to the magnetic moment of the Pt atom. © 1992.

X-ray resonance exchange scattering has been measured at the Nd L 2,3absorption edges on the (440) Bragg reflection in a ferromagnetic Nd2Fe14B single crystal. The magnetic spectrum at the L2-edge reflects the spin polarization of unoccupied 5d-bands of Nd due to electric dipole transitions. The magnetic spectrum at the L 3-edge shows a more complicated structure than that at the L 2-edge. The difference in magnetic spectra between the L2- and L3-edges is discussed from the viewpoints of LS coupling in 5d-bands and the contributions of electric quadrupole transitions to the highly localized and partially vacant 4f-states.