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Negative-spin-polarization material generates a spin current whose spin direction is opposite to the magnetization direction. This characteristicis technologically important because it can increase the freedom in the designof spintronic devices. In this paper, westudied FeCr from the viewpoints of the band structure, atomic magnetic moments, and local atomic arrangementto explore the potentiality as a negative-spin-polarization material. Thefirst-principlescalculation on the disordered FeCr alloypredicted a high negative spin polarization, whichis attributed to the band matching of the minority spin.We experimentally fabricated Fe1-xCrxthin film in the Cr-concentration (x) range from 0.2 to 0.4 by sputter deposition. The spin polarization of Fe0.7Cr0.3 estimated from current-perpendicular-to-plane giant magnetoresistance was −0.28 and fell below the calculated value. The synchrotron X-ray magnetic circular dichroism (XMCD)measurement showed the ferrimagnetic configuration of the magnetic moments of Fe and Cr. The Fe moment shows a large moment over the wide Cr concentration range, whereas the Cr moment decreased with the Cr concentration, which agrees with the calculation result. The synchrotron Mössbauer spectroscopy measurement indicated the inhomogeneity of the FeCr composition even in the as-deposited state. It was also found that Fe-rich region was formed after annealing, reflecting the phase separation nature of the FeCr system.The inhomogeneity was not considered in the calculation and could be the origin of the low spin polarization observed in the experiment.

We conducted in-situ high-pressure acoustic wave velocitymeasurements of Fe2+-bearing MgSiO3 glass up to 158 GPaby means of Brillouin scattering spectroscopy to understand the effect of iron on silicate melt in the lower mantle.Thechange in trend of the velocity profile, likely induced by the structural transition in Si-O coordination numberproposedin previous studies of silicate glasses, is also observed around 129 GPa. The transition pressurebecomes 125-128 GPa when considering the iron content of melts in a pyrolitic or chondritic mantle, whichis lower than the pressures of the CMB and the ULVZs. Our datashowthe substitution of 12mol% Fe in MgSiO3 glass decreases the VS by ~5.5 %. This study implies that iron considerably affect onthe buoyancy relations between melts/crystals and the iron-bearing melts at the lowermost mantle will have thehigher coordination numberthan sixfold.

We conducted in-situ high-pressure acoustic wave velocitymeasurements of Fe2+-bearing MgSiO3 glass up to 158 GPaby means of Brillouin scattering spectroscopy to understand the effect of iron on silicate melt in the lower mantle.Thechange in trend of the velocity profile, likely induced by the structural transition in Si-O coordination numberproposedin previous studies of silicate glasses, is also observed around 129 GPa. The transition pressurebecomes 125-128 GPa when considering the iron content of melts in a pyrolitic or chondritic mantle, whichis lower than the pressures of the CMB and the ULVZs. Our datashowthe substitution of 12mol% Fe in MgSiO3 glass decreases the VS by ~5.5 %. This study implies that iron considerably affect onthe buoyancy relations between melts/crystals and the iron-bearing melts at the lowermost mantle will have thehigher coordination numberthan sixfold.

Energy domain Mössbauer spectroscopy has been performing at the QST dedicated beamline (BL11XU) of SPring-8. In this presentation, I will introduce the present state of beamline operation, device performance including the nuclear Bragg monochromator, a brief introduction of applied research, future upgrade plans and research directions., Expert Workshop on Nuclear Resonant Scattering of Synchrotron Radiation

Raman scattering, Mossbauer spectroscopy, and X-ray diffraction measurements have revealed that EuHx compressed in high-pressure hydrogen exhibits the crystal structure changes and the divalent (Eu2+) to trivalent (Eu3+) changes via two Eu2+/Eu3+ mixed-valence phases: EuHx-I (Pnma, x=2, Eu2+) to EuHx-II (P63/mmc, x=2, 7.0 GPa, Eu2+) to EuHx-III (I4/m, x~2.2, 7.0−9.0 GPa, Eu2+/Eu3+) to EuHx-V (x~2.8, 9.0−12.4 GPa, Eu2+/Eu3+) to EuHx-VI (x~3, 12.4−14.4 GPa, Eu3+) to EuHx-VII (x~3, 14.4−16 GPa, Eu3+) to EuHx-IV (I4/mmm, x~3, 16 GPa−, Eu3+). The EuHx-II transforms to EuHx-III at a constant pressure near 7.0 GPa due to the reaction with hydrogen. Our results also demonstrate that Mossbauer spectroscopy can be a useful marker to detect the hydrogen storing in metal hydrides.

The surface magnetism of Fe(001) was studied in an atomic layer-by-layer fashion by using the in situ iron-57 probe layer method with a synchrotron Mössbauer source. The observed internal hyperfine field exhibits a marked decrease at the surface and an oscillatory behavior with increasing depth in the individual upper four layers below the surface. The calculated layer-depth dependencies of the effective hyperfine field, isomer shift, and quadrupole shift agree well with the observed experimental parameters. These results provide the first experimental evidence for the magnetic Friedel oscillations, which penetrate several layers from the Fe(001) surface.

An energy domain grazing incidence iron-57 Mössbauer spectroscopy with synchrotron radiation has been developed to study the local magnetic properties of magnetic thin films. A high-brilliant iron-57 Mössbauer radiation, filtered from synchrotron radiation by a iron borate single crystal nuclear Bragg monochromator, allows us to perform the grazing incidence Mössbauer spectroscopy for the iron-57 sub-monolayer in a mirror-like film. This presentation introduces the principles, advantages and two typical applications of local magnetic structure analysis using a synchrotron Mössbauer source, which includes the study of Morin transition of an iridium doped Fe2O3(111) thin film by using the grazing incidence synchrotron Mössbauer spectroscopy and a direct observation of the Friedel oscillation at the Fe(001) surface by using the in-situ iron-57 probe layer method. Undoubtedly, the outstanding potential of the energy domain grazing incidence iron-57 Mössbauer spectroscopy facilitate the study of surface and interface magnetism in advanced magnetic and spintronic materials and devices., 4th QST International Symposium

We measured the synchrotron-radiation (SR)-based Mössbauer spectra of Ni-based nanoparticles with a hexagonal structure that were synthesised by chemical reduction. To obtain Mössbauer spectra of the nanoparticles without (61)Ni enrichment, we developed a measurement system for (61)Ni SR-based Mössbauer absorption spectroscopy without X-ray windows between the (61)Ni84V16 standard energy alloy and detector. The counting rate of the (61)Ni nuclear resonant scattering in the system was enhanced by the detection of internal conversion electrons and the close proximity between the energy standard and the detector. The spectrum measured at 4 K revealed the internal magnetic field of the nanoparticles was 3.4 ± 0.9 T, corresponding to a Ni atomic magnetic moment of 0.3 Bohr magneton. This differs from the value of Ni3C and the theoretically predicted value of hexagonal-close-packed (hcp)-Ni and suggested the nanoparticle possessed intermediate carbon content between hcp-Ni and Ni3C of approximately 10 atomic % of Ni. The improved (61)Ni Mössbauer absorption measurement system is also applicable to various Ni materials without (61)Ni enrichment, such as Ni hydride nanoparticles.

The Mössbauer spectra of the 35.49 keV excited state of 125Te were observed in the energy domain using synchrotron radiation for the first time. The obtained isomer shifts and Debye temperature agree with previous experiments. These results show that this method will be applicable to various compounds.

A detection system for synchrotron-radiation (SR)-based Mössbauer spectroscopy was developed to enhance the nuclear resonant scattering counting rate and thus increase the available nuclides. In the system, a windowless avalanche photodiode (APD) detector was combined with a vacuum cryostat to detect the internal conversion (IC) electrons and fluorescent X-rays accompanied by nuclear de-excitation. As a feasibility study, the SR-based Mössbauer spectrum using the 76.5 keV level of 174Yb was observed without 174Yb enrichment of the samples. The counting rate was five times higher than that of our previous system, and the spectrum was obtained within 10 h. This result shows that nuclear resonance events can be more efficiently detected by counting IC electrons for nuclides with high IC coefficients. Furthermore, the windowless detection system enables us to place the sample closer to the APD elements and is advantageous for nuclear resonant inelastic scattering measurements. Therefore, this detection system can not only increase the number of nuclides accessible in SR-based Mössbauer spectroscopy but also allows the nuclear resonant inelastic scattering measurements of small single crystals or enzymes with dilute probe nuclides that are difficult to measure with the previous detection system.

BL11XU/SPring-8(原子力機構・専用ビームライン)では、ビームライン高度化の一環として、分光器に液体窒素循環冷却装置を導入するとともに、マルチ結晶交換システムを開発した。液体窒素冷却方法は、シリコン単結晶を液体窒素温度付近まで冷却することによって、シリコンの線膨張係数が小さくなり、また熱伝導率が大きくなる特性を利用するものである。BL11XUの研究のために、6-70keVの範囲で高輝度X線を得るためには、使用エネルギーによってSi(111)結晶とSi(311)結晶を使い分けるマルチ結晶交換システムを開発した。液体窒素循環による結晶の振動防止と液体窒素循環によるステージの過冷却防止措置も組み込んだ。その結果、これまで使用してきた人工合成ダイヤモンド結晶と比較して、14.4keVではおよそ7.4倍の強度を得ることができた。さらに、結晶交換と調整を、わずか5分以内で行うことができ、必要に応じていつでも結晶交換が可能となった。このマルチ結晶交換システムは上記の結晶だけではなく、色々な結晶にも応用でき大変有効である。, The liquid nitrogen circulation cooling device for a double crystal monochromator was introduced, and the multi-crystal switching system was developed on the JAEA dedicated beamline "BL11XU" at SPring-8. The multi-crystal switching system has features to be able to exchange crystals in cryogenic temperature and in a vacuum at any time. By this system, it is available to use high flux X-rays energy range of 6 to 70 keV., 著者所属: 日本原子力研究開発機構(JAEA), JAEA-Research 2009-009

放射光実験で用いられる分光結晶には単結晶が用いられ、その単結晶には高い結晶性が要求される。そのため、実験で利用する単結晶の光学的性能を見極めて、その有効性を図るために、事前に簡便かつ迅速に結晶性を定量評価しておく必要がある。そこでわれわれは量子ビーム応用研究部門・放射光科学研究ユニット内においてX線発生装置を用いた精密X線光学系を組立て、上記の結晶を一例とするさまざまな結晶の結晶性を評価することができるシステムを立ち上げた。このシステムにおいては、最小で試料サイズが数10mum程度の試料を測定可能で、1''以下での角度精度で測定が可能である。また、試料の位置を走査することで、試料内での結晶性の分布を測定することも可能である。本手法を用いて評価された鉄単結晶は、新たに開発された高分解能メスバウアー分光実験法においても利用されている。, Single crystal for experiment using by synchrotron radiation X-ray is needed to have high quality and performance as optics element. Therefore, quantitative estimation of performance of the single crystal must be done before the experiment. Precise X-ray optics system has been developed at JAEA/Quantum Beam Science Directorate/Synchrotron Radiation Unit at SPring-8. This system can measure small sample that is less than 0.01 mm in size, and have resolving ability of sample rotation that is less than 0.01 degree. And, scanning of sample, it is possible to measure distribution of quality at sample surface. For example, single crystal of FeBO3 which was measured by this system have been installed in synchrotron radiation M"ossbauer spectroscopy using Doppler-shifted 14.4 keV single line 57Fe-M"ossbauer radiation., 著者所属: 日本原子力研究開発機構(JAEA), JAEA-Technology 2009-035

日本原子力研究開発機構・量子ビーム応用研究部門・放射光科学研究ユニットでは、SPring-8の放射光を利用して行う高エネルギー分解能を要する特殊な実験に必要な結晶を製作するための技術的方法を確立させた。結晶の製作にあたっては、成形のための結晶加工装置と結晶面を測定するためのX線回折計を利用した。この製作法を用いて0.01度程度の角度精度を持って高分解能分光結晶やビームコリメーターなどを製作することができるようになったことで、ナノテクノロジー研究のような特殊な実験条件を必要とする放射光実験で利用できる環境が整備された。, Crystal processing methods of high resolution monochromator (HRM) has been developed at Japanese Atomic Energy Agency/Quantum Beam Science Directorate/Synchrotron Radiation Research unit at SPring-8. For producing HRM, slicing machine has been installed as cutting device of crystal ingot, and X-ray diffractmetor to measure the crystal face of the ingot has set up. By installation of these devices, high energy resolution monochromator crystal for inelastic X-ray scattering and beam collimator are got ready to be used for nanotechnology studies., 著者所属: 日本原子力研究開発機構(JAEA), JAEA-Technology 2006-056