Soft X-ray Magnetic Circular Dichroism Research Articles

Magnetic Analysis of Endohedral Metallofullerenes and Nano-Peapods by Soft X-ray Magnetic Circular Dichroism (MCD) Spectroscopy

not Available.

Magnetization reversal of uncompensated Fe moments in exchange biased Ni∕FeF2 bilayers

The magnetization reversal of uncompensated Fe moments in exchange biased Ni∕FeF2 bilayers was determined using soft x-ray magnetic circular and linear dichroism. The hysteresis loops resulting from the Fe moments are almost identical to those of the ferromagnetic Ni layer. However, a vertical loop shift indicates that some Fe moments are pinned in the antiferromagnetically ordered FeF2. The pinned moments are oriented antiparallel to small cooling fields, leading to negative exchange bias, but parallel to large cooling fields, resulting in positive exchange bias. No indication for the formation of a parallel antiferromagnetic domain wall in the FeF2 layer upon magnetization reversal in the Ni layer was found.

Thermal Phase Transformation of ZnO-Based Transparent Ferromagnetic Composite Films and the Change in Magnetic Characteristics

Transparent ferromagnetic semiconducting composite Fe–Zn–O films composed of wurtzite ZnO matrix and Zn-incorporated magnetite particles have been prepared by novel chemical solution processes followed by thermal annealing, performed at different temperatures between 200 and under vacuum at around . The effects of the thermal annealing on the structure and magnetic, electrical, and optical properties of the heterogranular transition metal oxides (Fe–Zn–O) films have been studied by using X-ray diffraction, X-ray absorption fine structure (XAFS), vibrating sample magnetometer, soft X-ray magnetic circular dichroism (SXMCD), and so on. These properties strongly depended on the annealing temperature and could be correlated to the changes in the ZnO matrix and/or the Zn-incorporated magnetite phase. The XAFS and SXMCD measurements using synchrotron radiation elucidated the growth process of the Zn-incorporated magnetite phase in the ZnO matrix.

Microstructure and Electronic Structure of Transparent Ferromagnetic ZnO−Spinel Iron Oxide Composite Films

Transparent ZnO films with ferromagnetic spinel iron oxide particles (Fe 9.5 atom %) were prepared on glass substrates by a novel chemical process followed by heat treatment at 773 K under vacuum. The chemical process involved (i) ZnO deposition from an aqueous solution and (ii) the introduction of iron atoms into the ZnO in another aqueous solution containing iron ions. The microstructure and electronic structure of the films were characterized in detail by using transmission electron microscope (TEM) analyses, X-ray absorption fine structure (XAFS), and soft X-ray magnetic circular dichroism (SXMCD). TEM observation revealed that the film had a heterogranular structure composed of iron oxide particles of 20 nm in diameter embedded in a wurtzite ZnO matrix. Both the Fe K-edge XAFS and Fe L 2,3 -edge SXMCD measurements using synchrotron radiation techniques indicated that the iron oxide particles were zinc-substituted magnetite (Zn x Fe 3-x O 4 , x ≈ 0.5) with a cubic spinel structure, which is the origin of ferromagnetism. Negative magnetoresistance of -0.35% was found at room temperature as well as an n-type semiconducting feature.

Soft X-Ray Magnetic Circular Dichroism Study of Ferromagnetic Uranium Compounds

Soft X-ray magnetic circular dichroism (XMCD) has been measured for ferromagnetic uranium monochalcogenides U X c ( X c = S, Se and Te) and UFe 2 . By applying the orbital and spin sum rules to the XMCD results, some trend has been found for the relationship between the ratio µ L /µ S and the total magnetic moment.

Sperri magnetism in amorphous rare-earth-transition metal perpendicular magnetic film: the application of a soft X-ray magnetic circular dichroism

Sperri magnetism in amorphous rare-earth-transition metal perpendicular magnetic film: the application of a soft X-ray magnetic circular dichroism

Element-specific magnetic moments in bccFe81Ni19∕Cosuperlattices

The magnetic moments in bcc Fe81Ni19/Co(001) superlattices with the individual layer thickness of 2-6 monolayers were studied by means of soft x-ray magnetic circular dichroism. It was found that t ...

Characterization of Transparent Ferromagnetic Fe:ZnO Semiconductor Films Chemically Prepared from Aqueous Solutions

Transparent magnetic semiconductor films were prepared on glass substrates by a novel chemical process involving (i) ZnO deposition from an aqueous solution and (ii) the introduction of Fe impurities into the ZnO in another aqueous solution. The former/latter aqueous solutions contain only zinc/iron nitrate and dimethylamine borane as reactants, and the reactions proceeded at low temperatures of under ambient atmosphere. The film with a characteristic wurtzite structure exhibited high transparency in the visible light region and room-temperature ferromagnetic behavior, as well as a semiconducting feature. Extended X-ray absorption fine structure and soft X-ray magnetic circular dichroism measurements using synchrotron radiation techniques and transmission electron microscopy analyses were performed to clarify the local structure around Fe impurities and the origin of room-temperature ferromagnetism. The incorporated Fe impurities were found to form nanosized zinc ferrite surrounding the hexagonal ZnO grains, and the zinc ferrite had an deficient nonstoichiometry, causing the room-temperature ferromagnetism.

Soft X-ray magnetic circular dichroism study of Al40Mn25Fe15Ge20 decagonal quasicrystal

Magnetic properties of a spin-glass Al40Mn25Fe15Ge20 decagonal quasicrystal (QC) have been studied by means of soft X-ray magnetic circular dichroism (MCD). Element specific magnetic hysteresis (ESMH) loops have been measured as magnetic field dependence of MCD intensity at the Mn and Fe L3-edges. A significant difference has been found in the ESMH loops between Mn and Fe in the QC, where only the Mn loop has an obvious remanent-like magnetization. This result of ESMH has suggested that Mn and Fe magnetic moments have different magnetic viscosities in the spin-glass QC. A ferromagnetic approximant-crystalline Al40Mn40Ge20 has also been investigated in comparison with the QC.

Revelation of Ni magnetic moment in GdNi single crystal by soft X-ray magnetic circular dichroism

Magnetic moment of Ni in GdNi single crystal was studied through the soft X-ray absorption spectra (XAS) and the magnetic circular dichroism (MCD) at the Ni L 2,3-edges and the Gd M 4,5-edges. Our experiment revealed for the first time that the Ni 3d band is not filled completely even at the content of 50 at.% of Gd and the Ni does retain a total magnetic moment coupling antiparallel to that of Gd. This result implied that the Ni in GdNi holds an intrinsic magnetic moment even at 50 at.% of Gd and contradicts the well-known charge transfer model. Further by employing the magneto-optical sum rule, the spin and orbital angular magnetic moment were evaluated and discussed.

Temperature dependence of the magnetocrystalline anisotropy energy and projected microscopic magnetic moments in epitaxialCrO2films

Soft x-ray magnetic circular dichroism spectra and in situ element specific hysteresis loops of epitaxially grown $\mathrm{Cr}{\mathrm{O}}_{2}$ thin films have been investigated in the temperature range from $25\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}330\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for two different crystallographic projections. The quantitative temperature dependence of the microscopic magnetic moments (spin, orbital, and magnetic dipole term) and the magnetocrystalline anisotropy energy give strong evidence for the validity of the models by Bruno and by van der Laan, which describe the generation of the orbital moment and its relation to the magnetic anisotropy energy.

Soft x-ray magnetic circular dichroism study of Cr tellurides

Ferromagnetic chromium tellurides Cr5Te6(δ=0.17) and Cr2Te3(δ=0.33) have been investigated by Cr 2p x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD). The observed XMCD spectra have been analyzed by means of a configuration-interaction cluster model calculation. From calculated results, we suggest that the doped holes created by the Cr deficiency exist mainly in the Te 5p orbital of Cr1−δTe.

Admixture of excited states and ground states of aEu3+ion inEu3Fe5O12by means of magnetic circular dichroism

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.

Ferromagnetic metal to spin-glass insulator transition in pyrochlore-type molybdates [formula omitted] Mo 2O7 studied with photoemission and XMCD

Pyrochlore-type molybdates R 2 Mo 2O7 (R = rare earth elements and Y), showing a ferromagnetic metal (FM) to spin-glass insulator (SGI) transition as a function of R, have been studied by means of photoemission spectrosocpy (PES) and soft X-ray magnetic circular dichroism (XMCD) with focusing on the role of the strong correlation of the Mo 4d electrons. Bulk sensitive PES was performed by utilizing the high-resolution soft X-ray from SPring-8. The PES spectra are compared with the band structure calculation. The XMCD spectra are analyzed by means of the sum-rule (Mo 3 p → 3 d XMCD) and by comparison with atomic calculation (R 3 d → 4 f XMCD) in order to estimate separately the Mo and R magnetic moments.

Development of a soft X-ray magnetic circular dichroism spectrometer using a 1.9 T electromagnet at BL25SU of SPring-8

A soft X-ray magnetic circular dichroism (SXMCD) spectrometer system using a water-cooled electromagnet of 1.9 T has been installed at BL25SU of SPring-8. The purpose is to develop an optimized system for element specific magnetization (ESM) measurements by means of SXMCD. A combination between the variable magnetic field and the helicity switching technique using the twin helical undulators gives a great advantage for measuring precise ESM loops. The present system is especially useful for investigations of magnetic properties on multi-layered thin films and ultra-thin films in addition to multi-elements alloys and compounds.

Mn 3d states in ferromagnetic semiconductor Ge 1− xMn xTe investigated by Mn 2p-3d soft X-ray magnetic circular dichroism spectroscopy

Mn 3d electronic structure in IV–VI ferromagnetic semiconductor Ge 1− x Mn x Te ( x = 0.32) has been investigated by means of the soft X-ray magnetic circular dichroism (XMCD) measurements of the Mn 2p-3d absorption spectra (XAS spectra). The XAS and XMCD spectra show a characteristic feature of the localized Mn 2+ 3d states. From the analyses of the spectra based on the configuration interaction theory, the parameters such as the p-d hybridization and p-d exchange constant N 0β are estimated.

Direct observation of the Fe substitution effect on the MCD spectra of the dysprosium iron garnet family

Soft x-ray magnetic circular dichroism (MCD) and absorption spectra (XAS) were measured at the Fe L2,3-edges and the Dy M4,5-edges for a family of dysprosium iron garnets. The Fe ions sit in either Oh symmetry sites or Td symmetry sites in Dy3Fe5O12. Only Fe ions in the Oh sites are substituted with In ions in Dy3Fe4.25In0.75O12 and only Fe ions in the Td sites are substituted with Ga ions in Dy3Fe4.25Ga0.75O12. The XAS spectrum profiles of the three-dysprosium iron garnets are very similar. The MCD signals of both the Fe L2,3-edges and the Dy M4,5-edges of Dy3Fe4.25Ga0.75O12 are similar to that of Dy3Fe5O12, but Dy3Fe4.25In0.75O12 is remarkably different. The results directly show that the spin moment of Fe in the Td sites play a major role in determining the total magnetization of Dy3Fe5O12.

Magnetic Dead Layers Induced by Strain at fct Fe/Rh(001) Interface

We have studied magnetic properties of face-centered-tetragonal (fct) Fe thin films grown at room temperature on the Rh(001) surface. Band structure calculations show that the stable magnetic phase of fct Fe on the Rh(001) surface is ferromagnetic (FM), which agrees with our previous conclusion obtained by angle-resolved photoelectron spectroscopy and spin- and angle-resolved photoelectron spectroscopy (SARPES) of the four monolayers (ML) Fe film [K. Hayashi et al. : Phys. Rev. B 64 (2001) 054417]. This magnetic phase of fct Fe is also confirmed by the SARPES spectra of 3 ML Fe/Rh(001). On the other hand the thickness dependence of the Curie temperature estimated by SARPES and of local magnetic moment by soft X-ray magnetic circular dichroism experiments show that the Fe films below 2 ML are not FM, i.e., they are magnetic dead layers. We conclude that these magnetic dead layers are caused by a large strain at the Fe/Rh(001) interface.

Electronic structure ofCr1‐δX(X=S,Te)studied by Cr2psoft x-ray magnetic circular dichroism

Cr 2p core excited XAS and XMCD spectra of ferromagnetic Cr$_{1-\delta}$Te with several concentrations of $\delta$=0.11-0.33 and ferrimagnetic Cr$_{5}$S$_{6}$ have been measured. The observed XMCD lineshapes are found to very weakly depend on $\delta$ for Cr$_{1-\delta}$Te. The experimental results are analyzed by means of a configuration-interaction cluster model calculation with consideration of hybridization and electron correlation effects. The obtained values of the spin magnetic moment by the cluster model analyses are in agreement with the results of the band structure calculation.The calculated result shows that the doped holes created by the Cr deficiency exist mainly in the Te 5porbital of Cr$_{1-\delta}$Te, whereas the holes are likely to be in Cr 3d state for Cr$_{5}$S$_{6}$.

Magnetic dead layers in Fe films induced by a lattice mismatch at an interface

The magnetism of Fe thin films grown at room temperature on the Rh(0 0 1) surface was studied by angle- and spin-resolved photoemission, X-ray photoelectron diffraction, soft X-ray magnetic circular dichroism (XMCD), and band calculations using full-potential augmented plane wave method. On the Rh(0 0 1) surface Fe films start to grow in a FCT(0 0 1) structure with a lattice constant compressed along the direction perpendicular to the surface and the compression is gradually released as the film thickness increases. The characteristic growth mode of the Fe films on the Rh(0 0 1) surface results in the existence of magnetically dead 2 monolayers (ML) of Fe at the interface and of ferromagnetism over 2 ML , which are realized by the XMCD experiments measured at low temperature. The thickness dependence of the magnetic properties of the Fe films is consistent with the results of total energy calculations adopting the experimentally obtained interlayer spacing.