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We fabricated two types of cobalt-ferrite (001) thin films, insulative Fe-rich cobalt-ferrite CoxFe3-xO4+{\delta} (I-CFO) and conductive Fe-rich cobalt-ferrite CoyFe3-yO4 (C-CFO), with perpendicular magnetic anisotropy (PMA) on MgO (001) substrates. Although the stoichiometric cobalt-ferrite is known as an insulating material, it is found that the conductivity of Fe-rich cobalt-ferrites can be controlled by changing the source materials and deposition conditions in the pulsed laser deposition technique. The I-CFO and C-CFO films exhibit PMA through the in-plane lattice distortion. We investigated the Fe-ion-specific valence states in both I-CFO and C-CFO films by M\"ossbauer spectroscopy and X-ray magnetic circular dichroism, and found that the difference in conductivity corresponds to the abundance ratio of Fe2+ state at the octahedral B-site (Oh) in the inverse spinel structure. Furthermore, first-principles calculations reproduce the changes in the density of states at the Fermi level depending on the cation vacancies at the B-site, which explains the difference in the conductivity between I-CFO and C-CFO., Comment: 21 pages including 8 figures

We report room-temperature (RT) magnetoresistance (MR) in a novel Fe-based perovskite, SrV

Diodes, memories, logic circuits, and most other current information technologies rely on the combined use of p- and n-type semiconductors. Although oxide semiconductors have many technologically attractive functionalities, such as transparency and high dopability to enable their use as conducting films, they typically lack bipolar conductivity. In particular, the absence of p-type semiconducting properties owing to the innate electronic structures of oxides represents a bottleneck for the development of practical devices. Here, bipolar semiconducting properties are demonstrated in α-SnWO4 within a 100 °C temperature window after appropriate thermal treatment. Comprehensive spectroscopic observations reveal that Sn4+ is present in p-type α-SnWO4 in a notably greater quantity than in n-type. This result strongly suggests that the Sn4+ substitutional defects on the W6+ sites contribute to hole-carrier generation in α-SnWO4. We also find that oxygen vacancies are initially formed in Sn-O-W bonds and migrate to W-O-W bonds with changes in semiconducting properties from p-type to n-type. These findings suggest useful strategies for exploring p-type oxide semiconductors and controlling their carrier type by utilizing the octahedral structure.

We demonstrated the generation of perpendicularly spin-polarized electronic currents using a tunnel spin-filtering effect through insulative Fe-rich cobalt ferrite Co xFe3− xO4+δ (I-CFO) barriers with perpendicular magnetic anisotropy (PMA). The I-CFO films grown on conductive Fe-rich cobalt ferrite Co yFe3− yO4 (C-CFO) films, which were deposited on additional I-CFO buffer layers on MgO(001) substrates, exhibited PMA induced by an epitaxial strain. Magnetic tunnel junctions (MTJs), which comprise C-CFO electrode layers, I-CFO barrier layers, and perpendicularly magnetized Co/{Tb/Co}15/Co spin detection layers, showed a tunnel magnetoresistance (TMR) effect. This indicated that spin-polarized tunnel currents were injected into the spin detection layers. A spin injection efficiency of −28% was observed for the MTJs with an I-CFO barrier of 3.0 nm in thickness at 100 K. The voltage dependence of the TMR effect indicates that the spin-injection efficiency is affected by voltage-dependent changes in the effective spin-dependent barrier width. The combination of spinel-type C-CFO and I-CFO films with well-controlled compositions and lattice strains is, therefore, applicable as a spin-injection source for spintronics devices when perpendicularly spin-polarized electronic currents are required.

We successfully fabricated perpendicularly magnetized cobalt-ferrite Co x Fe 3 - x O 4 + δ (0 0 1) films on nonmagnetic metal TiN (0 0 1) films. We found that the in-plane lattice constant of the Co x Fe 3 - x O 4 + δ (0 0 1) films was larger than the out-of-plane lattice constant. This lattice strain induced perpendicular magnetic anisotropy, and square hysteresis curves were observed in out-of-plane magnetic fields for the Co x Fe 3 - x O 4 + δ (x = 0.4 ∼ 0.6) films. With the decrease of the Co composition from x = 1 to x = 0, the Co x Fe 3 - x O 4 + δ films approached not to conductive Fe 3 O 4 but to insulating γ - Fe 2 O 3 accompanying cation vacancies in the cubic spinel structure. The good tunneling conductivity character was observed for the Co x Fe 3 - x O 4 + δ tunnel junctions. The results open up a possibility that insulating Co x Fe 3 - x O 4 + δ films can be applied to elements of perpendicularly magnetized spintronics devices.

Diodes, memories, logic circuits, and most other current information technologies rely on the combined use of p- and n-type semiconductors. Although oxide semiconductors have many technologically attractive functionalities, such as transparency and high dopability to enable their use as conducting films, they typically lack bipolar conductivity. In particular, the absence of p-type semiconducting properties owing to the innate electronic structures of oxides represents a bottleneck for the development of practical devices. Here, bipolar semiconducting properties are demonstrated in α-SnWO

PbMO3 (M = 3d transition metals) family shows systematic variations in charge distribution and intriguing physical properties due to its delicate energy balance between Pb 6s and transition metal 3d orbitals. However, the detailed structure and physical properties of PbFeO3 remain unclear. Herein, we reveal that PbFeO3 crystallizes into an unusual 2ap × 6ap × 2ap orthorhombic perovskite super unit cell with space group Cmcm. The distinctive crystal construction and valence distribution of Pb2+0.5Pb4+0.5FeO3 lead to a long range charge ordering of the -A-B-B- type of the layers with two different oxidation states of Pb (Pb2+ and Pb4+) in them. A weak ferromagnetic transition with canted antiferromagnetic spins along the a-axis is found to occur at 600 K. In addition, decreasing the temperature causes a spin reorientation transition towards a collinear antiferromagnetic structure with spin moments along the b-axis near 418 K. Our theoretical investigations reveal that the peculiar charge ordering of Pb generates two Fe3+ magnetic sublattices with competing anisotropic energies, giving rise to the spin reorientation at such a high critical temperature., PbFeO3 is part of a family of lead based perovskites with many intriguing properties; however, difficulties in synthesis have hampered investigation. Here, the authors present a detailed study of the structure of PbFeO3 observing unique charge ordering and spin orientation among the constituent ions.

Multistep spin crossover (SCO) compounds have attracted much attention, since they can be great candidates for high-density multinary memory devices. The introduction of substituents, such as methyl (Me), chloro (Cl), bromo (Br), and methoxy (MeO) groups, at para positions to the phenyl-substituted tripodal N

Wide-gap oxides with their valence band maximum (VBM) composed of s orbitals are essential for realizing practical p-type transparent oxide semiconductors. We prepared a new p-type wide-gap oxide, SnNb2O6 foordite, with its VBM composed of Sn 5s orbitals. To discuss carrier generation, we prepared both p-type and n-type SnNb2O6 by controlling the annealing conditions. The carrier mobility and density were 3.8 × 10–1 cm2 V–1 s–1 and 3.7 × 1018 cm–3, respectively, for the p-type sample and 9.9 cm2 V–1 s–1 and 7.5 × 1015 cm–3, respectively, for the n-type sample. The crystal structure of SnNb2O6 foordite consists of two types of alternating layers, Sn and Nb2O6 octahedra, where three nonequivalent oxygen sites exist. Six oxygens in the chemical formula of SnNb2O6 are distributed at the three sites in pairs, where the oxygens in three nonequivalent sites were named O1–O3. Hole and electron carriers were considered to be generated by Sn4+-on-Nb5+ substitutional defects (SnNb′) and oxygen vacancies of O1 and O2...

Hybrid improper ferroelectricity, which utilizes nonpolar but ubiquitous rotational/tilting distortions to create polarization, offers an attractive route to the discovery of new ferroelectric and multiferroic materials because its activity derives from geometric rather than electronic origins. Design approaches blending group theory and first principles can be utilized to explore the crystal symmetries of ferroelectric ground states, but in general, they do not make accurate predictions for some important parameters of ferroelectrics, such as Curie temperature (TC). Here, we establish a predictive and quantitative relationship between TC and the Goldschmidt tolerance factor, t, by employing n = 2 Ruddlesden–Popper (RP) A3B2O7 as a prototypical example of hybrid improper ferroelectrics. The focus is placed on an RP system, (Sr1–xCax)3Sn2O7 (x = 0, 0.1, and 0.2), which allows for the investigation of the purely geometric (ionic size) effect on ferroelectric transitions, due to the absence of the second-ord...

We investigated local magnetism at the interface between Co2FeGe Heusler alloy and Ag by 57Fe Mossbauer spectroscopy. Interface-sensitive samples, where the 57Fe isotope was used only for several interfacial atomic layers of the Co2FeGe layer on the Ag layer, were prepared using atomically controlled alternate deposition at various deposition temperatures. The 57Fe Mossbauer spectra measured at room temperature indicated that the interface region of the Co2FeGe layers for the samples deposited below 500 ° C retains the ferromagnetic B2 structure. On the other hand, interdiffusion between the Co2FeGe and Ag layers occurs and a nonmagnetic phase grows for the samples deposited at the substrate temperature higher than 550 ° C. We observed magnetoresistance (MR) ratio of 3.6% at room temperature for Co2FeGe/Ag/Fe current-perpendicular-to-plane giant-magnetoresistive (CPP-GMR) structures grown at 300 ° C, whereas we could not observe distinct MR effect for samples grown at 600 ° C. These results support that the existence of interfacial nonmagnetic phase due to the interdiffusion between Heusler alloy and nonmagnetic-metal layers severely reduces the performance of CPP-GMR devices.

X-ray absorption near edge structure (XANES) measurement is one of the most powerful tools for the evaluation of a cation valence state. XANES measurement is sometimes the only available technique for the evaluation of the valence state of a dopant cation, which often occurs in phosphor materials. The validity of the core excitation process should be examined as a basis for understanding the applicability of this technique. Here, we demonstrate the validity of valence estimation of tin in oxide glasses, using Sn K-edge and L-edge XANES spectra, and compare the results with 119Sn Mössbauer analysis. The results of Sn K-edge XANES spectra analysis reveal that this approach cannot evaluate the actual valence state. On the contrary, in LII-edge absorption whose transition is 2p1/2-d, the change of the white line corresponds to the change of the valence state of tin, which is calculated from the 119Sn Mössbauer spectra. Among several analytical approaches, valence evaluation using the peak area, such as the absorption edge energy E0 at the fractions of the edge step or E0 at the zero of the second derivative, is better. The observed findings suggest that the valence state of a heavy element in amorphous materials should be discussed using several different definitions with error bars, even though L-edge XANES analyses are used.

Using the electric field to manipulate the magnetization of materials is a potential way of making low-power-consumption nonvolatile magnetic memory devices. Despite concentrated effort in the last 15 years on magnetic multilayers and magnetoelectric multiferroic thin films, there has been no report on the reversal of out-of-plane magnetization by an electric field at room temperature without the aid of an electric current. Here, we report direct observation of out-of-plane magnetization reversal at room temperature by magnetic force microscopy after electric polarization switching of cobalt-substituted bismuth ferrite thin film grown on (110)o-oriented GdScO3 substrate. A striped pattern of ferroelectric and weakly ferromagnetic domains was preserved after reversal of the out-of-plane electric polarization.

We investigated the relation between the domain wall (DW) configuration and the strength of the interlayer exchange coupling (IEC) in multilayered magnetic wires, where a Ru spacer layer mediates the IEC between two ferromagnetic layers, and a Pt cap layer contributes to the interfacial Dzyaloshinskii–Moriya interaction. It was found that the antiferromagnetic IEC stabilizes the Neel-type DWs in the wires and that the stability varies with the strength of the antiferromagnetic IEC. The micromagnetic simulations imply that the Neel-type DWs are stabilized because the rotation of the magnetic moments in the DWs is restricted in the antiferromagnetically coupled ferromagnetic layers.

We report the substitution of manganese or scandium as a third element into the B-site of multiferroic BiFe0.9Co0.1O3 thin film in the ABO3 perovskite structure. Stable electric polarization switching via a biased cantilever was achieved multiple times in the BiFe0.892Co0.1Mn0.008O3 and BiFe0.87Co0.1Sc0.03O3 on SrTiO3 (001) while the piezoresponse force microscope (PFM) image after the poling was inhomogeneous and was not reversible in BiFe0.9Co0.1O3 thin film on SrTiO3 (001). Although the electric domains are fragmented by Mn substitution, magnetization reversal by electric field was observed in the BiFe0.892Co0.1Mn0.008O3 thin film as well as in the BiFe0.9Co0.1O3 on GdScO3 (110) studied previously.

Hybrid improper ferroelectricity, which utilizes nonpolar but ubiquitous rotational/tilting distortions to create polarization, offers an attractive route to the discovery of new ferroelectric and multiferroic materials because its activity derives from geometric rather than electronic origins. Design approaches blending group theory and first principles can be utilized to explore the crystal symmetries of ferroelectric ground states, but in general, they do not make accurate predictions for some important parameters of ferroelectrics, such as Curie temperature ( T

The authors report on luminescence of SnO-doped 60ZnO–40B2O3 (SZB) glasses melted in air and Ar atmosphere. In photoluminescence (PL), excitation spectra consist of two excitation bands, and the lo...

We have investigated the nano-structure of TiO 2 -precipitated CaO-B 2 O 3 -Bi 2 O 3 -Al 2 O 3 -TiO 2 (CaBBAT) glass–ceramics, and discussed the effect of the addition of SnO. 119 Sn Mossbauer spectra of the Sn-doped glass suggest that most of the SnO was oxidized during melting. Selective crystallization of TiO 2 occurred independently of SnO addition in the homogeneous glass. However, EDX analysis of the glass–ceramics revealed that the Ti cation is partially localized and that the addition of SnO promotes the nano-phase separation. It can be concluded, therefore, that the addition of SnO influenced the formation of secondary particles of TiO 2 nano-crystallites and thereby improved the photocatalytic activity.

Energy-domain57Fe polarization-dependent synchrotron radiation Mössbauer spectroscopy was developed by using a diamond X-ray phase plate and an iron borate nuclear Bragg monochromator. The former controls the polarization of the incident synchrotron radiation X-rays and the latter filters the57Fe-Mössbauer radiation with a narrow bandwidth of ∼3.4 Γ0(Γ0≃ 4.7 neV: natural linewidth of the57Fe nucleus) from the broadband synchrotron radiation. The developed nuclear diffraction optics allowed57Fe-Mössbauer studies to be performed with various polarization states,i.e.linear polarization, circular polarization and non-polarization. In this paper, the spectrometer system, beam characterization, performance-test experiments and a grazing-incidence Mössbauer measurement of an isotope-enriched (57Fe: 95%) iron thin film are described.

We analyzed the M-H loop observed for Fe 3 O 4 /bcc-Fe(001) junctions with thin insertion layers of Co or Mn by using several models that include bilinear and biquadratic coupling and twisting of magnetization near the interface. Both biquadratic and twisting of the magnetization are found to be important for explaining the M-H loop. To clarify the mechanism of antiparallel (AP) coupling in the Fe 3 O 4 /bcc-Fe junction, we performed first-principles calculations for junctions with and without extra Fe atoms on hollow sites of the spinel lattice at the interface. It was shown that parallel coupling is stable for junctions without extra Fe atoms whereas AP coupling becomes stable when the number of extra Fe atoms increases. The results suggest that magnetic frustration may occur when a nonuniform distribution of the extra Fe atoms exists at the interface.

The Morin transition of very thin Ir-doped α-Fe2O3 films, which is not detectable with conventional magnetization measurements, was studied by conversion electron Mossbauer spectroscopy using a 57Co source and nuclear resonant scattering using a synchrotron light source. It was found that (i) the Morin transition temperature increases as the Ir ratio increases, (ii) it decreases when the film thickness decreases, and (iii) the transition becomes irreversible when Ir ratio is small and the thickness is thin. These tendencies were found reproducible and systematic, although the mechanisms are to be clarified by further studies.

Synchrotron-radiation-based Mossbauer spectroscopy that yields absorption type Mossbauer spectra has been applied to various isotopes. This method enables the advanced measurement by using the excellent features of synchrotron radiation, such as Mossbauer spectroscopic measurement under high-pressures. Furthermore, energy selectivity of synchrotron radiation allows us to measure 40K Mossbauer spectra, of which observation is impossible by using ordinary radioactive sources because the first excited state of 40K is not populated by any radioactive parent nuclides. Moreover, this method has flexibility of the experimental setup that the measured sample can be used as a transmitter or a scatterer, depending on the sample conditions. To enhance the measurement efficiency of the spectroscopy, we developed a detection system in which a windowless avalanche photodiode (APD) detector is combined with a vacuum cryostat to detect internal conversion electrons adding to X-rays accompanied by nuclear de-excitation. In particular, by selecting the emission from the scatterer sample, depth selective synchrotron-radiation-based Mossbauer spectroscopy is possible. Furthermore, limitation of the time window in the delayed components enables us to obtain narrow linewidth in Mossbauer spectra. Measurement system that records velocity dependent time spectra and energy information simultaneously realizes the depth selective and narrow linewidth measurement.

By controlling lattice defects through the annealing condition during crystal growth, a wide-gap and $p$-type semiconductor ${\mathrm{Sn}}_{2}({\mathrm{Nb}}_{2\text{\ensuremath{-}}x}{\mathrm{Ta}}_{x}){\mathrm{O}}_{7}$ $(x=$ $0--2)$ was developed. The band gap is variable in the range from 2.4 eV for ${\mathrm{Sn}}_{2}{\mathrm{Nb}}_{2}{\mathrm{O}}_{7}$ $(x=0)$ to 3.0 eV for ${\mathrm{Sn}}_{2}{\mathrm{Ta}}_{2}{\mathrm{O}}_{7}$ $(x=2)$, respectively. The carrier density and the hole mobility were estimated to be $0.20--1.4$ $(\ifmmode\times\else\texttimes\fi{}{10}^{18}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})$ and $0.28--1.9$ $(\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}1}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1})$, respectively. From the mutual relation between the defect content and the electrical properties, we concluded that the hole carriers in the $p$-type semiconducting ${\mathrm{Sn}}_{2}({\mathrm{Nb}}_{2\text{\ensuremath{-}}x}{\mathrm{Ta}}_{x}){\mathrm{O}}_{7}$ are generated by ${\mathrm{Sn}}^{4+}$-on-${\mathrm{Nb}}^{5+}/{\mathrm{Ta}}^{5+}$ substitutional defects in (Nb,${\mathrm{Ta})}_{2}{\mathrm{O}}_{6}$ octahedral chains.

A combined analysis of Ir-doped α-Fe2O3 (001) films, which show a drastic enhancement in the Morin transition temperature as a result of Ir doping, was performed by employing X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and Mossbauer spectroscopy analyses at room temperature. The Mossbauer spectra reveal that the valency of Fe remains 3+ after Ir doping. The XANES spectra indicate that the valency of the Ir ion in Ir-doped α-Fe2O3 varies from 3+ to 4+. The EXAFS analysis results clarified that the Ir ions occupy the Fe-sites of α-Fe2O3. These findings help elucidate the mechanism for controlling the Morin transition temperature in α-Fe2O3 films toward antiferromagnetic spintronic applications.

Considering the importance of magneto-elastic (ME) effects on the magnetic anisotropy (MA) of thin films, phenomenological analysis of the MA of Co ferrites on (001) and (111) substrates is conducted. It is found that thin films of Co ferrites on (111) substrates may produce oblique magnetization, while those on (001) substrates exhibit perpendicular MA. First-principles calculations for the ME constant of L10 ordered alloys, which show large uniaxial MA, are also performed, and it is determined that the value of the ME constant is on the same order of magnitude as that for the Co ferrites.

Applications of synchrotron-radiation-based Mossbauer spectroscopy in the “energy domain” to the studies on magnetism of thin films are introduced on the basis of the experiments recently performed at SPring-8, Japan. The measured samples are spintronics-related thin films, such as Co2MnSn films, layered Fe/Cr films, layered Fe/Fe3O4 films, and Fe4N films. The validity of the energy domain measurements is demonstrated in the light of industrial applications of magnetic thin films.

Daylight-driven photocatalysts have attracted much attention in the context of "green" technology. Although various active materials have been reported and their applications are rapidly increasing, many are discovered after enormous experimental efforts. Herein the discovery of a novel oxide photocatalyst, β-SnMoO[4], is demonstrated via a rational search of 3483 known and hypothetical compounds with various compositions and structures over the whole range of SnO-MO[q/2] (M: Ti, Zr, and Hf (q = 4); V, Nb, and Ta (q = 5); Cr, Mo, and W (q = 6)) pseudobinary systems. Screening using thermodynamic stability, band gap, and band-edge positions by density functional theory calculations identifies β-SnMoO[4] as a potential target. Then a low temperature route is used to successfully synthesize the novel crystal, which is confirmed by X-ray powder diffraction and Mössbauer spectroscopy. β-SnMoO[4] is active for the photocatalytic decomposition of a methylene blue solution under daylight and its activity is comparable to a known photocatalyst, β-SnWO[4]., 高効率スクリーニングによる新しい2価スズ酸化物系光触媒材料の発見. 京都大学プレスリリース. 2016-09-14.

Daylight‐driven photocatalysts have attracted much attention in the context of “green” technology. Although various active materials have been reported and their applications are rapidly increasing, many are discovered after enormous experimental efforts. Herein the discovery of a novel oxide photocatalyst, β‐SnMoO4, is demonstrated via a rational search of 3483 known and hypothetical compounds with various compositions and structures over the whole range of SnO‐MOq /2 (M: Ti, Zr, and Hf (q = 4); V, Nb, and Ta (q = 5); Cr, Mo, and W (q = 6)) pseudobinary systems. Screening using thermodynamic stability, band gap, and band‐edge positions by density functional theory calculations identifies β‐SnMoO4 as a potential target. Then a low temperature route is used to successfully synthesize the novel crystal, which is confirmed by X‐ray powder diffraction and Mössbauer spectroscopy. β‐SnMoO4 is active for the photocatalytic decomposition of a methylene blue solution under daylight and its activity is comparable to a known photocatalyst, β‐SnWO4.

The coexistence and coupling of ferromagnetic and ferroelectric orders in a single material is crucial for realizing next-generation multifunctional applications. The coexistence of such orders is confirmed at room temperature in epitaxial thin films of BiFe

The spin structure in BiFe1−xCoxO3 (\(x = 0.05,0.10,0.15,0.20\)) was investigated as a function of Co substitution, temperature, and magnetic field. It was found that the cycloidal spin structure of BiFeO3 changed to a collinear one with spin canting and composition-independent spontaneous magnetization of ∼0.25 μB/f.u. for the Co substituted samples on heating. The collinear phase was stabilized under magnetic fields. The spin structure change was clarified also by the temperature dependence of 57Fe Mossbauer spectra, and the results indicated the first order nature of this transition.

Our recent work has demonstrated that well-defined hollow interiors can be created inside Prussian Blue (PB) nanoparticles through controlled chemical etching in the presence of poly(vinylpyrrolidone) (Angew. Chem., Int. Ed.2012, 51, 984). By calcination of these PB nanoparticles as starting precursors, we can successfully synthesize nanoporous iron oxides with hollow interiors. From scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the original hollow cavities of PB nanocubes are shown to be retained after crystal transformation to iron oxides. Also, the obtained hollow iron oxides show a very high surface area because of their nanoporous shells, as illustrated by N2 gas adsorption–desorption analysis. By tuning the applied calcination temperatures and selecting the PB nanoparticles with different hollow cavities, crystalline α-Fe2O3, and γ-Fe2O3 can be selectively formed in the products without formation of any impurity phases. Field-dependent magnetization measurements indi...

Energy-domain grazing-incidence (57)Fe-Mossbauer spectroscopy (E-GIMS) with synchrotron radiation (SR) has been developed to study surface and interface structures of thin films. Highly brilliant (57)Fe-Mossbauer radiation, filtered from SR by a (57)FeBO(3) single-crystal nuclear Bragg monochromator, allows conventional Mossbauer spectroscopy to be performed for dilute (57)Fe in a mirror-like film in any bunch-mode operation of SR. A theoretical and experimental study of the specular reflections from isotope-enriched ((57)Fe: 95%) and natural-abundance ((57)Fe: ∼2%) iron thin films has been carried out to clarify the basic features of the coherent interference between electronic and nuclear resonant scattering of (57)Fe-Mossbauer radiation in thin films. Moreover, a new surface- and interface-sensitive method has been developed by the combination of SR-based E-GIMS and the (57)Fe-probe layer technique, which enables us to probe interfacial complex magnetic structures in thin films with atomic-scale depth resolution.

A synchrotron radiation (SR) Mossbauer spectrometer has been developed by using a nuclear Bragg monochromator (NBM). It enables energy-domain 57Fe SR-Mossbauer spectroscopy (SRMS). Doppler-shifted SR-Mossbauer radiation is produced by pure nuclear Bragg reflection (PNBR) from an oscillating 57FeBO3 crystal near the Neel point. In this paper, we describe the optics and its applications, including high-pressure SRMS, grazing incidence SRMS and γ-ray diffraction studies with the Rayleigh scattering of Mossbauer radiation (RSMR) method.

Thin films of Bi m + 1 Fe m − 3 Ti 3 O 3 m + 3 (BFTO) with m ≦ 9 have been successfully grown on (100) SrTiO 3 by chemical solution deposition. These films had the c axis normal to the film plane. The conversion electron Mossbauer spectoroscopy (CEMS) showed that the spectra of BFTO thin films exhibit an asymmetric quadrupole doublet for m = 8 at 300 K, indicative of being paramagnetic, while, for m = 9, clearly show six hyperfine lines indicating presence of magnetic order at 300 K. From the intensity ratio of asymmetric peaks, the polarization axis of BFTO films with m ≥ 8 was deduced to be likely along of the perovskite-like unit. On the other hand, it was found from the spectral fitting that the BFTO thin film with m = 9 has the Neel temperature around 310 K and the spin axis making an angle of about 60° to the c- axis. These indicate that the BFTO ( m = 9) thin film is a promising candidate for room-temperature multiferroics.

The evolution of crystal structure, spin structure, and macroscopic magnetization of manganese-substituted BiFeO3 (BiFe1−xMnxO3), a candidate for multiferroic materials, were investigated on bulk and epitaxial thin-film. Mn substitution for Fe induced collinear antiferromagnetic spin structure around room temperature by destabilizing the cycloidal spin modulation which prohibited the appearance of net magnetization generated by Dzyaloshinskii-Moriya interaction. For the bulk samples, however, no significant signal of ferromagnetism was observed because the direction of the ordered spins was close to parallel to the electric polarization so that spin-canting did not occur. On the contrary, BiFe1−xMnxO3 thin film on SrTiO3 (001) had a collinear spin structure with the spin direction perpendicular to the electric polarization at room temperature, where the appearance of spontaneous magnetization was expected. Indeed, ferromagnetic hysteresis behavior was observed for BiFe0.9Mn0.1O3 thin film.

Fe and Si hybrid clusters are co-deposited on substrates in a double-glow-discharge-source-type plasma-gas-condensation system, and observed by transmission electron microscopy, scanning transmission electron microscopy, X-ray diffraction and Mossbauer spectroscopy. Core-shell Fe/Si clusters, in which chemically heterogeneous bcc Fe-Si cores are covered by amorphous-like Si shells, are obtained on the substrate when Fe and Si cluster nuclei collide with each other at an early stage (without setting the partition plate between the two sources). On the other hand, Fe and Si clusters are juxtaposed on the substrate when their nuclei collide with each other at a late stage (with setting of the partition plate). These results demonstrate that we can obtain various hybridized states of Fe and Si clusters by controlling the collision stages.

Co 2 TiSn Heusler alloy films were grown on MgO substrates at the substrate temperature between 200 and 600 °C using atomically controlled alternate deposition and magnetic hyperfine field at the Sn nuclei was measured by the Mossbauer spectroscopy and the nuclear resonant scattering method. The relation between the hyperfine field and the structural disorder estimated by X-ray diffraction measurements was also examined. The results showed that the sample prepared at higher substrate temperature has higher degree of L2 1 order and larger hyperfine field. For the Co 2 TiSn film grown at 600 °C, the hyperfine field estimated from the oscillatory pattern of the nuclear resonant time spectra was 6.1 T at room temperature and increased with a decrease of temperature to 7.5, 8.1, and 8.3 T at 200, 100, and 5 K, respectively, which shows that the film prepared by this method and condition has almost the same magnetization value and Curie temperature as bulk samples.