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In a conventional magnetic material, a long-range magnetic order develops in three dimensions, and reducing a layer number weakens its magnetism. Here we demonstrate anomalous layer-number-independent ferromagnetism down to the two-dimensional (2D) limit in a metastable phase of Cr

We carried out angle-resolved photoemission (ARPES) experiments using soft x rays to investigate the electronic structure of the intermediate-valence compound ${\mathrm{EuNi}}_{2}{\mathrm{P}}_{2}$. Both the ${\mathrm{Eu}}^{2+}$ and ${\mathrm{Eu}}^{3+}$ components arising from the $4{f}^{6}$ and $4{f}^{5}$ final states were observed in the valence spectra, directly confirming an intermediate-valence character of Eu ions. The three-dimensional band structure was studied by ARPES measurements, and the ARPES results were compared with calculations based on the density-functional theory for the non-4$f$ reference compounds ${\mathrm{SrNi}}_{2}{\mathrm{P}}_{2}$ and ${\mathrm{YNi}}_{2}{\mathrm{P}}_{2}$. We found that the ARPES spectra up to just below the Fermi level are better reproduced by the calculation of ${\mathrm{SrNi}}_{2}{\mathrm{P}}_{2}$ rather than that of ${\mathrm{YNi}}_{2}{\mathrm{P}}_{2}$. The heavy-fermion bands in ${\mathrm{EuNi}}_{2}{\mathrm{P}}_{2}$ are thus considered to be formed through the hybridization between the dispersive valence bands, which resemble those for ${\mathrm{SrNi}}_{2}{\mathrm{P}}_{2}$, and the ${\mathrm{Eu}}^{2+}$ components located at the very vicinity of the Fermi level.

The discoveries of intrinsic ferromagnetism in atomically-thin van der Waals crystals have opened up a new research field enabling fundamental studies on magnetism at two-dimensional (2D) limit as well as development of magnetic van der Waals heterostructures. To date, a variety of 2D ferromagnetism has been explored mainly by mechanically exfoliating 'originally ferromagnetic (FM)' van der Waals crystals, while bottom-up approach by thin film growth technique has demonstrated emergent 2D ferromagnetism in a variety of 'originally non-FM' van der Waals materials. Here we demonstrate that V5Se8 epitaxial thin films grown by molecular-beam epitaxy (MBE) exhibit emergent 2D ferromagnetism with intrinsic spin polarization of the V 3d electrons despite that the bulk counterpart is 'originally antiferromagnetic (AFM)'. Moreover, thickness-dependence measurements reveal that this newly-developed 2D ferromagnet could be classified as an itinerant 2D Heisenberg ferromagnet with weak magnetic anisotropy, broadening a lineup of 2D magnets to those potentially beneficial for future spintronics applications.

We investigate near-Fermi-energy (${E}_{F}$) element-specific electronic and spin states of ferromagnetic van der Waals (vdW) metal ${\mathrm{Fe}}_{5}\mathrm{Ge}{\mathrm{Te}}_{2}$. The soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) measurement provides spectroscopic evidence of localized Fe $3d$ band. We also find prominent hybridization between the localized Fe $3d$ band and the delocalized Ge/Te $p$ bands. This picture is strongly supported from direct observation of the remarkable spin polarization of the ligand $p$ bands near ${E}_{F}$, using x-ray magnetic circular dichroism (XMCD) measurements. The strength of XMCD signal from ligand element Te shows the highest value, as far as we recognize, among literature reporting finite XMCD signal for nonmagnetic element in any systems. Combining SX-ARPES and elemental selective XMCD measurements, we collectively point to an important role of giant spin polarization of the delocalized ligand Te states for realizing itinerant long-range ferromagnetism in ${\mathrm{Fe}}_{5}\mathrm{Ge}{\mathrm{Te}}_{2}$. Our finding provides a fundamental elemental selective viewpoint for understanding mechanism of itinerant ferromagnetism in low-dimensional compounds, which also leads to insight for designing exotic magnetic states by interfacial band engineering in heterostructures.

Magnetocrystalline anisotropy, a key ingredient for establishing long-range order in a magnetic material down to the two-dimensional (2D) limit, is generally associated with spin-orbit interaction (SOI) involving a finite orbital angular momentum. Here we report strong out-of-plane magnetic anisotropy without orbital angular momentum, emerging at the interface between two different van der Waals (vdW) materials, an archetypal metallic vdW material NbSe2 possessing Zeeman-type SOI and an isotropic vdW ferromagnet V5Se8. We found that the Zeeman SOI in NbSe2 induces robust out-of-plane magnetic anisotropy in V5Se8 down to the 2D limit with a more than 2-fold enhancement of the transition temperature. We propose a simple model that takes into account the energy gain in NbSe2 in contact with a ferromagnet, which naturally explains our observations. Our results demonstrate a conceptually new magnetic proximity effect at the vdW interface, expanding the horizons of emergent phenomena achievable in vdW heterostructures.

Fe-doped III-V ferromagnetic semiconductors (FMSs) such as (In,Fe)As, (Ga,Fe)Sb, (In,Fe)Sb, and (Al,Fe)Sb are promising materials for spintronic device applications because of the availability of both n- and p-type materials and the high Curie temperatures. On the other hand, (Ga,Fe)As, which has the same zinc-blende crystal structure as the Fe-doped III-V FMSs, shows paramagnetism. The origin of the different magnetic properties in the Fe-doped III-V semiconductors remains to be elucidated. To address this issue, we use resonant photoemission spectroscopy (RPES) and x-ray magnetic circular dichroism (XMCD) to investigate the electronic and magnetic properties of the Fe ions in a paramagnetic (Ga$_{0.95}$,Fe$_{0.05}$)As thin film. The observed Fe 2$p$-3$d$ RPES spectra show that the Fe 3$d$ states are similar to those of ferromagnetic (Ga,Fe)Sb. The estimated Fermi level is located in the middle of the band gap in (Ga,Fe)As. The Fe $L_{2,3}$ XMCD spectra of (Ga$_{0.95}$,Fe$_{0.05}$)As show pre-edge structures, which are not observed in the Fe-doped FMSs, indicating that the minority-spin ($\downarrow$) $e_\downarrow$ states are vacant in (Ga$_{0.95}$,Fe$_{0.05}$)As. The XMCD results suggest that the carrier-induced ferromagnetic interaction in (Ga$_{0.95}$,Fe$_{0.05}$)As is short-ranged and weaker than that in the Fe-doped FMSs. The experimental findings suggest that the electron occupancy of the $e_\downarrow$ states contributes to the appearance of ferromagnetism in the Fe-doped III-V semiconductors, for p-type as well as n-type compounds.

Magnetic transition metal dichalcogenide (TMD) films have recently emerged as promising candidates in hosting novel magnetic phases relevant to next-generation spintronic devices. However, systematic control of the magnetization orientation, or anisotropy, and its thermal stability characterized by Curie temperature $({T}_{\mathrm{C}})$, remains to be achieved in such films. Here we present self-intercalated epitaxial ${\mathrm{Cr}}_{1+\ensuremath{\delta}}{\mathrm{Te}}_{2}$ films as a platform for achieving systematic/smooth magnetic tailoring in TMD films. Using a molecular-beam epitaxy based technique, we have realized epitaxial ${\mathrm{Cr}}_{1+\ensuremath{\delta}}{\mathrm{Te}}_{2}$ films with smoothly tunable \ensuremath{\delta} over a wide range (0.33--0.82), while maintaining NiAs-type crystal structure. With increasing \ensuremath{\delta}, we found monotonic enhancement of ${T}_{\mathrm{C}}$ from 160 to 350 K, and the rotation of magnetic anisotropy from out-of-plane to in-plane easy-axis configuration for fixed film thickness. Contributions from conventional dipolar and orbital moment terms are insufficient to explain the observed evolution of magnetic behavior with \ensuremath{\delta}. Instead, ab initio calculations suggest that the emergence of antiferromagnetic interactions with \ensuremath{\delta}, and its interplay with conventional ferromagnetism, may play a key role in the observed trends. This demonstration of tunable ${T}_{\mathrm{C}}$ and magnetic anisotropy across room temperature in TMD films paves the way for engineering different magnetic phases for spintronic applications.

X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) spectroscopy were applied at the Ge (Ga) ${L}_{2,3}$ edge to unravel the spin-resolved unoccupied electronic states of ${\mathrm{Co}}_{2}\mathrm{Mn}\mathrm{Ge}$ (Ga). Complicated spectral features were observed in both XAS and XMCD spectra. For their interpretation, we compared the experimental XAS and XMCD spectra with the calculated Ge (Ga) $4s$ and $4d$ orbital partial density of states. The comparison enabled a qualitative explanation of the XMCD spectra as the difference between the majority- and minority-spin unoccupied density of states summed over the $4s$ and $4d$ orbitals. Our finding provides a new approach to uncover the spin-split partial density of states above the Fermi level.

(Ga,Fe)Sb is a promising ferromagnetic semiconductor for practical spintronic device applications because its Curie temperature $({T}_{\mathrm{C}})$ is above room temperature. However, the origin of ferromagnetism with high ${T}_{\mathrm{C}}$ remains to be elucidated. Here, we use soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) to investigate the valence-band (VB) structure of $(\mathrm{G}{\mathrm{a}}_{0.95},\mathrm{F}{\mathrm{e}}_{0.05})\mathrm{Sb}$ including the $\mathrm{Fe}\text{\ensuremath{-}}3d$ impurity band (IB), to unveil the mechanism of ferromagnetism in (Ga,Fe)Sb. We find that the VB dispersion in $(\mathrm{G}{\mathrm{a}}_{0.95},\mathrm{F}{\mathrm{e}}_{0.05})\mathrm{Sb}$ observed by SX-ARPES is similar to that of GaSb, indicating that the doped Fe atoms hardly affect the band dispersion. The $\mathrm{Fe}\text{\ensuremath{-}}3d$ resonant ARPES spectra demonstrate that the $\mathrm{Fe}\text{\ensuremath{-}}3d$ IB crosses the Fermi level $({E}_{\mathrm{F}})$ and hybridizes with the VB of GaSb. These observations indicate that the VB structure of $(\mathrm{G}{\mathrm{a}}_{0.95},\mathrm{F}{\mathrm{e}}_{0.05})\mathrm{Sb}$ is consistent with that of the IB model which is based on double-exchange interaction between the localized $3d$ electrons of the magnetic impurities.

Spintronics devices utilizing a magnetic domain-wall motion have attracted increasing attention, and ferrimagnetic materials with almost-compensated magnetic moments are highly required to realize the fast magnetic domain-wall motion. Here, we report a key function for this purpose in the antiperovskite $\mathrm{C}{\mathrm{o}}_{x}\mathrm{M}{\mathrm{n}}_{4\ensuremath{-}x}\mathrm{N}$ film. We have grown $\mathrm{C}{\mathrm{o}}_{x}\mathrm{M}{\mathrm{n}}_{4\ensuremath{-}x}\mathrm{N}$ films with various Co/Mn ratios on $\mathrm{SrTi}{\mathrm{O}}_{3}(001)$ by molecular-beam epitaxy. High-quality growth is confirmed and a perpendicular magnetization emerges at $x=0$, 0.2, 0.5, and 0.8, whereas it turns into in plane for $x\ensuremath{\ge}1.1$. The saturation magnetization ${M}_{S}$ decreases as $x$ increases and reaches a minimum value of $15\phantom{\rule{0.16em}{0ex}}\mathrm{emu}/\mathrm{c}{\mathrm{m}}^{3}$ at $x=0.8$. Then, it increases with $x$ when $0.8\ensuremath{\le}x\ensuremath{\le}3.6$ and saturates. These results indicate that ${M}_{S}$ and magnetic anisotropy of $\mathrm{C}{\mathrm{o}}_{x}\mathrm{M}{\mathrm{n}}_{4\ensuremath{-}x}\mathrm{N}$ films can be manipulated by the Co composition. X-ray absorption spectroscopy and magnetic circular dichroism measurements revealed that Co atoms tend to occupy the I site in the antiperovskite lattice and reasonably explains the origin of minimum ${M}_{S}$ near $x=0.8$, where a compensation of magnetic moments occurs among different atomic sites. We consider that the nearly compensated ferrimagnetic $\mathrm{C}{\mathrm{o}}_{0.8}\mathrm{M}{\mathrm{n}}_{3.2}\mathrm{N}$ is suitable for application to current-induced domain-wall motion devices.

Materials that possess nontrivial topology and magnetism is known to exhibit exotic quantum phenomena such as the quantum anomalous Hall effect. Here, we fabricate a novel magnetic topological heterostructure Mn4Bi2Te7/Bi2Te3 where multiple magnetic layers are inserted into the topmost quintuple layer of the original topological insulator Bi2Te3. A massive Dirac cone (DC) with a gap of 40–75 meV at 16 K is observed. By tracing the temperature evolution, this gap is shown to gradually decrease with increasing temperature and a blunt transition from a massive to a massless DC occurs around 200–250 K. Structural analysis shows that the samples also contain MnBi2Te4/Bi2Te3. Magnetic measurements show that there are two distinct Mn components in the system that corresponds to the two heterostructures; MnBi2Te4/Bi2Te3 is paramagnetic at 6 K while Mn4Bi2Te7/Bi2Te3 is ferromagnetic with a negative hysteresis (critical temperature ~20 K). This novel heterostructure is potentially important for future device applications., T.H. was supported by JSPS KAKENHI Grant Number 18H03877, the Murata Science Foundation (No. H30-084), the Asahi Glass Foundation, Tokyo Tech. Challenging Research Award, and the Iketani Science and Technology Foundation (No. 0321083-A). M.K. was supported by the Spintronics Research Network of Japan (Spin-RNJ). The ARPES measurements were performed under the UVSOR proposal Nos. 29-837, 30-571, 30-860 and the SARPES measurements were performed under the HiSOR proposal No. 16BG001. The XMCD measurements were performed at JAEA beamline BL-23SU in SPring-8 (Proposal No. 2018B3843) and also at PF-KEK (PF PAC No. 17P006). The work at SPring-8 was performed under the Shared Use Program of JAEA Facilities (Proposal No. 2018B-E21) with the approval of Nanotechnology Platform project supported by the Ministry of Education, Culture, Sports, Science and Technology (Proposal No. A-18-AE-0039). The support by Tomsk State University competitiveness improvement program (No. 8.1.01.2018), the Saint Petersburg State University (Project ID 51126254), the Russian Science Foundation (Grant No. 18-12-00169) and the Government research assignment for ISPMS SB RAS, project No. III.23.2.9 is gratefully acknowledged. M.M.O. acknowledges the support by Spanish Ministerio de Ciencia e Innovación (Grant No. PID2019-103910GB-I00).

Fundamental understanding of interfacial magnetic properties in ferromagnetic heterostructures is essential to utilize ferromagnetic materials for spintronic device applications. In this paper, we investigate the interfacial magnetic and electronic structures of epitaxial single-crystalline LaAlO$_3$ (LAO)/La$_{0.6}$Sr$_{0.4}$MnO$_3$ (LSMO)/Nb:SrTiO$_3$ (Nb:STO) heterostructures with varying LSMO-layer thickness, in which the magnetic anisotropy strongly changes depending on the LSMO thickness due to the delicate balance between the strains originating from both the Nb:STO and LAO layers, using x-ray magnetic circular dichroism (XMCD) and photoemission spectroscopy (PES). We successfully detect the clear change of the magnetic behavior of the Mn ions concomitant with the thickness-dependent metal-insulator transition (MIT). Our results suggest that double-exchange interaction induces the ferromagnetism in the metallic LSMO film under tensile strain caused by the SrTiO$_3$ substrate, while superexchange interaction determines the magnetic behavior in the insulating LSMO film under compressive strain originating from the top LAO layer. Based on those findings, the formation of a magnetic dead layer near the LAO/LSMO interface is attributed to competition between the superexchange interaction via Mn 3$d_{3z^2-r^2}$ orbitals under compressive strain and the double-exchange interaction via the 3$d_{x^2-y^2}$ orbitals., Comment: 20 pages, 6 figures

We investigated the magnetic properties of multiferroic hexagonal ErFeO3 thin films by using x-ray magnetic circular dichroism (XMCD) and synchrotron Mössbauer spectroscopy. In order to reveal the element-specific magnetic properties, temperature-dependent XMCD experiments were conducted at the Fe L 2,3 and Er M 4,5-edges. Apparent magnetic hysteresis loops appear for both ions below the Néel temperature, which suggests the existence of ferromagnetism. The temperature evolutions of the coercive field and spontaneous magnetization for both ions show similar behavior. These results indicate that Fe ions influence the magnetism of Er ions. Our results deepen the understanding of the physical properties of hexagonal rare-earth ferrite system.

The discoveries of intrinsic ferromagnetism in atomically thin van der Waals crystals have opened a new research field enabling fundamental studies on magnetism at two-dimensional (2D) limit as well as development of magnetic van der Waals heterostructures. Currently, a variety of 2D ferromagnetism has been explored mainly by mechanically exfoliating "originally ferromagnetic (FM)" van der Waals crystals, while a bottom-up approach by thin-film growth technique has demonstrated emergent 2D ferromagnetism in a variety of "originally non-FM" van der Waals materials. Here we demonstrate that V

Resonant photoelectron spectroscopy at the Co and Mn $2p$ core absorption edges of half-metallic ${\mathrm{Co}}_{2}\mathrm{MnGe}$ has been performed to determine the element-specific density of states (DOS). A significant contribution of the Mn $3d$ partial DOS near the Fermi level $({E}_{\mathrm{F}})$ was clarified by measurement at the Mn $2p$ absorption edge. Further analysis by first-principles calculation revealed that it has ${t}_{2\mathrm{g}}$ symmetry, which must be responsible for the electrical conductivity along the line perpendicular to the film plane. The dominant normal Auger contribution observed at the Co $2p$ absorption edge indicates delocalization of photoexcited Co $3d$ electrons. The difference in the degrees of localization of the Mn $3d$ and Co $3d$ electrons in ${\mathrm{Co}}_{2}\mathrm{MnGe}$ is explained by the first-principles calculation. Our findings of the element-/orbital-specific electronic states near ${E}_{\mathrm{F}}$ will pave the way for future interface design of magnetic tunneling junctions to overcome the temperature-induced reduction of the magnetoresistance.

The electronic structure and the magnetism of the ferromagnetic semiconductor (Ga,Fe)Sb, whose Curie temperature ${T}_{\mathrm{C}}$ can exceed room temperature, were investigated by means of x-ray absorption spectroscopy (XAS), x-ray magnetic circular dichroism (XMCD), and resonance photoemission spectroscopy (RPES). The line-shape analyses of the XAS and XMCD spectra suggest that the ferromagnetism is of intrinsic origin. The orbital magnetic moments deduced using XMCD sum rules were found to be large, indicating that there is a considerable $3{d}^{6}$ contribution to the ground state of Fe. From RPES, we observed a strong dispersive Auger peak and nondispersive resonantly enhanced peaks in the valence-band spectra. The latter is a fingerprint of the correlated nature of Fe $3d$ electrons, whereas the former indicates their itinerant nature. It was also found that the Fe $3d$ states have a finite contribution to the density of states at the Fermi energy. These states, presumably consisting of majority-spin $p\text{\ensuremath{-}}d$ hybridized states or minority-spin $e$ states, would be responsible for the ferromagnetic order in this material.

We have carried out angle-integrated photoemission spectroscopy (AIPES) and angle-resolved photoemission spectroscopy (ARPES) experiments using soft x rays on single crystals of ${\mathrm{EuCu}}_{2}{\mathrm{Ge}}_{2}$ and ${\mathrm{EuCu}}_{2}{\mathrm{Si}}_{2}$ grown by the Bridgman method to investigate their electronic structures. The AIPES results showed that the Eu ions in ${\mathrm{EuCu}}_{2}{\mathrm{Ge}}_{2}$ and ${\mathrm{EuCu}}_{2}{\mathrm{Si}}_{2}$ are in a divalent state and a nearly trivalent state, respectively, in accordance with the previously reported magnetic properties. The three-dimensional band structures and shapes of the Fermi surfaces of ${\mathrm{EuCu}}_{2}{\mathrm{Ge}}_{2}$ and ${\mathrm{EuCu}}_{2}{\mathrm{Si}}_{2}$ were studied by ARPES measurements. We found that the band structures near the Fermi level and Fermi surfaces of ${\mathrm{EuCu}}_{2}{\mathrm{Ge}}_{2}$ and ${\mathrm{EuCu}}_{2}{\mathrm{Si}}_{2}$ are very different from each other and are well reproduced by the band structure calculations based on density-functional theory for ${\mathrm{SrCu}}_{2}{\mathrm{Ge}}_{2}$ and ${\mathrm{YCu}}_{2}{\mathrm{Si}}_{2}$. This suggests that a charge transfer from the localized $4f$ states into the valence bands is responsible for the difference in the electronic states between ${\mathrm{EuCu}}_{2}{\mathrm{Ge}}_{2}$ and ${\mathrm{EuCu}}_{2}{\mathrm{Si}}_{2}$.

Ferromagnetic topological insulators have emerged as a promising platform for quantum anomalous Hall (QAH) effect with a dissipationless edge transport. However, the observation of QAH effect has so far been restricted to extremely low temperatures. We investigate the microscopic origin of ferromagnetism coupled with topological insulators in vanadium-doped (Sb, Bi)(2)Te-3 employing the x-ray magnetic circular dichroism, angle-resolved two-photon photoemission spectroscopy, combined with first-principles calculations. We found a negative spin polarization, and thus an antiparallel magnetic moment at the Te site with respect to that of the vanadium dopants, which plays the key role in the ferromagnetic order. We ascribe it to the hybridization between Te p and V d majority spin states at the Fermi energy (E-F), being supported by a Zener-type p-d exchange interaction scenario. The substitution of Bi at the Sb site suppresses the bulk ferromagnetism by introducing extra electron carriers in the majority spin channel of Te p states that compensates the antiparallel magnetic moment on the Te site. Our findings reveal important clues to designing magnetic topological insulators with higher Curie temperature that work under ambient conditions.

We have elucidated the nature of the electron correlation effect in uranium compounds by imaging the partial $\mathrm{U}\phantom{\rule{4pt}{0ex}}5f$ density of states (pDOS) of typical itinerant, localized, and heavy fermion uranium compounds by using the $\mathrm{U}\phantom{\rule{4pt}{0ex}}4d\text{\ensuremath{-}}5f$ resonant photoemission spectroscopy. The obtained $\mathrm{U}\phantom{\rule{4pt}{0ex}}5f$ pDOS exhibit a systematic trend depending on the physical properties of compounds. The coherent peak at the Fermi level can be described by the band-structure calculation, but an incoherent peak emerges on the higher binding energy side ($\ensuremath{\lesssim}1\phantom{\rule{4pt}{0ex}}\mathrm{eV}$) in the $\mathrm{U}\phantom{\rule{4pt}{0ex}}5f$ pDOS of localized and heavy fermion compounds. As the $\mathrm{U}\phantom{\rule{4pt}{0ex}}5f$ state is more localized, the intensity of the incoherent peak is enhanced and its energy position is shifted to higher binding energy. These behaviors are consistent with the prediction of the Mott metal-insulator transition, suggesting that the Hubbard-$U$ type mechanism takes an essential role in the $5f$ electronic structure of actinide materials.

In order to understand the mechanism of the ferromagnetism in the ferromagnetic semiconductor Ga 1 − xMn xAs [(Ga,Mn)As], we have investigated the magnetic behavior on a microscopic level through systematic temperature ( T)- and magnetic field ( H)-dependent soft x-ray magnetic circular dichroism (XMCD) experiments at the Mn L 2 , 3 absorption edges. The T and H dependences of XMCD intensities have been analyzed using a model consisting of the ferromagnetic (FM), paramagnetic, and superparamagnetic (SPM) components. Intriguingly, we have found a common behavior for the ferromagnetic ordering process in (Ga,Mn)As samples with different Mn concentrations (4% and 10.8%) and different Curie temperature ( T C) values (65, 120, and 164 K). In particular, the SPM component develops well above T C, indicating that local FM regions are formed well above T C. The present findings indicate that the onset of ferromagnetic ordering is triggered by local electronic states around the substitutional Mn ions rather than uniform electronic states considered by mean-field theories. Insight into the most representative ferromagnetic semiconductor, (Ga,Mn)As, provided by the present study will be an important step in understanding the mechanism of ferromagnetic ordering in various ferromagnetic semiconductor families.

EuPd3 is a rare Eu-based compound, whose Eu ions are in a trivalent state. The electronic structure of EuPd3 was investigated by angle-resolved photoemission spectroscopy (ARPES) using soft x rays....

We have performed soft x-ray magnetic circular dichroism (XMCD) experiments on the itinerant-electron metamagnet UCoAl at the U $4d\ensuremath{-}5f({N}_{4,5})$ and Co $2p\ensuremath{-}3d({L}_{2,3})$ absorption edges in order to investigate the magnetic properties of the U $5f$ and Co $3d$ electrons separately. From the line shape of the XMCD spectrum, it is deduced that the orbital magnetic moment of the Co $3d$ electrons is unusually large. Through the systematic temperature $(T)$- and magnetic field $(H)$-dependent XMCD measurements, we have obtained two types of the magnetization curve as a function of $H$ and $T$ (M-H curve and M-T curve, respectively). The metamagnetic transition from a paramagnetic state to a field-induced ferromagnetic state was clearly observed under 15 K at ${H}_{\mathrm{M}}$. The value of the ${H}_{\mathrm{M}}$ and its $T$ dependence agree well between the U and Co sites, and the bulk magnetization. Whereas, we have discovered the remarkable differences in the M-H and M-T curves between the U and Co sites. The present findings clearly show that the role of the Co $3d$ electrons should be considered more carefully in order to understand the origin of the magnetic ordering in UCoAl.

X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism measurements were performed at the Ni and Fe ${L}_{2,3}$ absorption edges for $\mathrm{N}{\mathrm{i}}_{x}\mathrm{F}{\mathrm{e}}_{4\ensuremath{-}x}\mathrm{N}\phantom{\rule{4pt}{0ex}}(x=1$ and 3) epitaxial films. Spectral line-shape analysis and element-specific magnetic moment evaluations are presented. Shoulders at approximately 2 eV above the Ni ${L}_{2,3}$ main peaks in the XAS spectrum of $\mathrm{N}{\mathrm{i}}_{3}\mathrm{FeN}$ were interpreted to originate from hybridization of orbitals between Ni $3d$ at face-centered (II) sites and N $2p$ at body-centered sites, while such features were missing in $\mathrm{NiF}{\mathrm{e}}_{3}\mathrm{N}$ film. Similar shoulders were observed at Fe ${L}_{2,3}$ edges in both films. These results indicate that the orbitals of Ni atoms did not hybridize with those of N atoms in the $\mathrm{NiF}{\mathrm{e}}_{3}\mathrm{N}$ film. Hence, Ni atoms preferentially occupied corner (I) sites, where the hybridization was weak because of the relatively long distance between Ni at I sites and N atoms. The relatively large magnetic moment deduced from sum-rule analysis of $\mathrm{NiF}{\mathrm{e}}_{3}\mathrm{N}$ also showed a good agreement with the presence of Ni atoms at I sites.

We have studied the electronic structure of ferrimagnetic ${\mathrm{Mn}}_{2}\mathrm{VAl}$ single crystals by means of soft x-ray absorption spectroscopy (XAS), x-ray absorption magnetic circular dichroism (XMCD), and resonant soft x-ray inelastic scattering (RIXS). We have successfully observed the XMCD signals for all the constituent elements. The Mn ${L}_{2,3}$ XAS and XMCD spectra are reproduced by spectral simulations based on density-functional theory, indicating the itinerant character of the Mn $3d$ states. On the other hand, the V $3d$ electrons are rather localized since the ionic model can qualitatively explain the V ${L}_{2,3}$ XAS and XMCD spectra. This picture is consistent with local $dd$ excitations revealed by the V ${L}_{3}$ RIXS.

The electronic structures of $\mathrm{U}{X}_{3}$ ($X=\mathrm{Al}, \mathrm{Ga}$, and $\mathrm{In}$) were studied by photoelectron spectroscopy to understand the relationship between their electronic structures and magnetic properties. The band structures and Fermi surfaces of ${\mathrm{UAl}}_{3}$ and ${\mathrm{UGa}}_{3}$ were revealed experimentally by angle-resolved photoelectron spectroscopy (ARPES), and they were compared with the result of band-structure calculations. The topologies of the Fermi surfaces and the band structures of ${\mathrm{UAl}}_{3}$ and ${\mathrm{UGa}}_{3}$ were explained reasonably well by the calculation, although bands near the Fermi level (${E}_{\mathrm{F}}$) were renormalized owing to the finite electron correlation effect. The topologies of the Fermi surfaces of ${\mathrm{UAl}}_{3}$ and ${\mathrm{UGa}}_{3}$ are very similar to each other, except for some minor differences. Such minor differences in their Fermi surface or electron correlation effect might take an essential role in their different magnetic properties. No significant changes were observed between the ARPES spectra of ${\mathrm{UGa}}_{3}$ in the paramagnetic and antiferromagnetic phases, suggesting that ${\mathrm{UGa}}_{3}$ is an itinerant weak antiferromagnet. The effect of chemical pressure on the electronic structures of $\mathrm{U}{X}_{3}$ compounds was also studied by utilizing the smaller lattice constants of ${\mathrm{UAl}}_{3}$ and ${\mathrm{UGa}}_{3}$ than that of ${\mathrm{UIn}}_{3}$. The valence band spectrum of ${\mathrm{UIn}}_{3}$ is accompanied by a satellitelike structure on the high-binding-energy side. The core-level spectrum of ${\mathrm{UIn}}_{3}$ is also qualitatively different from those of ${\mathrm{UAl}}_{3}$ and ${\mathrm{UGa}}_{3}$. These findings suggest that the $\mathrm{U}\phantom{\rule{4pt}{0ex}}5f$ states in ${\mathrm{UIn}}_{3}$ are more localized than those in ${\mathrm{UAl}}_{3}$ and ${\mathrm{UGa}}_{3}$.

Epitaxial $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ bilayers are expected to be highly efficient spin injectors into Si owing to the spin filter effect of $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}$. To exploit the full potential of this system, understanding the microscopic origin of magnetically dead layers at the $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ interface is necessary. In this paper, we study the cation distribution, electronic structures, and the magnetic properties of $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}(111)$ layers with various thicknesses (thickness $d=1.4$, 2.3, 4, and 11 nm) in the epitaxial $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}(111)/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}(111)/\mathrm{Si}(111)$ structures using soft x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) combined with cluster-model calculation. The magnetization of $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}$ measured by XMCD gradually decreases with decreasing thickness $d$, and finally, a magnetically dead layer is clearly detected at $d=1.4\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$. The magnetically dead layer has frustration of magnetic interactions, which is revealed from comparison between the magnetizations at 300 and 6 K. From analysis using configuration-interaction cluster-model calculation, the decrease of $d$ leads to a decrease in the inverse-to-normal spinel structure ratio and also a decrease in the average valence of Fe at the octahedral sites. These results strongly indicate that the magnetically dead layer at the $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ interface originates from various complex networks of superexchange interactions through the change in the cation distribution and electronic structure. Furthermore, from comparison of the magnetic properties between $d=1.4$ and 2.3 nm, it is found that the ferrimagnetic order of the magnetically dead layer at the $\mathrm{CoF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ interface is partially restored by increasing the thickness from $d=1.4$ to 2.3 nm.

The electronic structure of ThRu2Si2 was studied by angle-resolved photoelectron spectroscopy (ARPES) with incident photon energies of hn=655-745 eV. Detailed band structure and the three-dimensional shapes of Fermi surfaces were derived experimentally, and their characteristic features were mostly explained by means of band structure calculations based on the density functional theory. Comparison of the experimental ARPES spectra of ThRu2Si2 with those of URu2Si2 shows that they have considerably different spectral profiles particularly in the energy range of 1 eV from the Fermi level, suggesting that U 5f states are substantially hybridized in these bands. The relationship between the ARPES spectra of URu2Si2 and ThRu2Si2 is very different from the one between the ARPES spectra of CeRu2Si2 and LaRu2Si2, where the intrinsic difference in their spectra is limited only in the very vicinity of the Fermi energy. The present result suggests that the U 5f electrons in URu2Si2 have strong hybridization with ligand states and have an essentially itinerant character.

${\mathrm{Ge}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}$ (Ge:Fe) shows ferromagnetic behavior up to a relatively high temperature of 210 K and hence is a promising material for spintronic applications compatible with Si technology. Unlike the prototypical system (Ga,Mn)As where itinerant holes induce long-range ferromagnetic order of the Mn spins, however, its ferromagnetism evolves from robust nanoscale ferromagnetic domains formed in Fe-rich regions. We have studied its underlying electronic structure by soft x-ray angle-resolved photoemission spectroscopy measurements and first-principles supercell calculation. We observed finite Fe $3d$ components in the states at the Fermi level $({E}_{\mathrm{F}})$ in a wide region of momentum space, and the ${E}_{\mathrm{F}}$ was located $\ensuremath{\sim}0.35$ eV above the valence-band maximum of the host Ge. Our calculation indicates that the ${E}_{\mathrm{F}}$ is also within the deep acceptor-level impurity band induced by the strong $p\text{\ensuremath{-}}d({t}_{2})$ hybridization. We conclude that the additional minority-spin $d(e)$ electron characteristic of the ${\mathrm{Fe}}^{2+}$ state is responsible for the short-range ferromagnetic coupling between Fe atoms, making the magnetism markedly different from that of (Ga,Mn)As.

$\mathrm{G}{\mathrm{e}}_{1\ensuremath{-}x}\mathrm{M}{\mathrm{n}}_{x}$ (GeMn) granular thin films are a unique and promising material for spintronic applications owing to their large positive magnetoresistance (MR). Previous studies of GeMn have suggested that the large MR is related to the nanospinodal decomposition of GeMn into Mn-rich ferromagnetic nanoparticles and a Mn-poor paramagnetic matrix. However, the microscopic origin of the MR has not yet been clarified. Here, we develop a method to separately investigate the magnetic properties of the nanoparticles and the matrix, utilizing the extremely high sensitivity of x-ray magnetic circular dichroism (XMCD) to the local magnetic state of each atom. We find that the MR ratio is proportional to the product of the magnetizations originating from the nanoparticles and the matrix. This result indicates that the spin-polarized holes in the nanoparticles penetrate into the matrix and that these holes undergo first order magnetic scattering by the paramagnetic Mn atoms in the matrix, which induces the large MR.

Quantum anomalous Hall effect (QAHE) is a key phenomenon for low power-consumption device applications owing to its dissipationless spin-polarized and quantized current in the absence of an external magnetic field. However, the recorded working temperature of the QAHE is still very low. Here we systematically investigate the magnetic dopants induced modifications from the view points of magnetic, structural and electronic properties and the ultrafast carrier dynamics in a series of V-doped Sb2Te3 samples of composition Sb2−x V x Te3 with x = 0, 0.015 and 0.03. Element specific x-ray magnetic circular dichroism signifies that the ferromagnetism of V-doped Sb2Te3 is governed by the p–d hybridization between the host carrier and the magnetic dopant. Time- and angle-resolved photoemission spectroscopy excited with mid-infrared pulses has revealed that the V impurity induced states underlying the topological surface state (TSS) add scattering channels that significantly shorten the duration of transient surface electrons down to the 100 fs scale. This is in a sharp contrast to the prolonged duration reported for pristine samples though the TSS is located inside the bulk energy gap of the host in either magnetic or non-magnetic cases. It implies the presence of a mobility gap in the bulk energy gap region of the host material that would work toward the robust QAHE. Our findings shed light on the material design for low-energy-consuming device applications.

We have studied the electronic structure of the molecular ferromagnet β -Mn phthalocyanine ( β -MnPc) in a polycrystalline form, which has been reported to show ferromagnetism at T 8.6 K , by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). From the experimental results and subsequent cluster-model calculation, we find that the ferromagnetic Mn ion in β -MnPc is largely in the 4 E g ground state arising from the ( e g ) 3 ( b 2 g ) 1 ( a 1 g ) 1 [ ( d x z , y z ) 3 ( d x y ) 1 ( d z 2 ) 1 ] configuration of the Mn2+ state. Considering that the highest occupied molecular orbital (HOMO) of MnPc with the 4 E g ground state originates from the a 1 g orbital of the Mn2+ ion, it is proposed that a 1 g – a 1 g exchange coupling via the π orbitals of the phthalocyanine ring plays a crucial role in the ferromagnetism of β -MnPc.

We have performed x-ray photoemission spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and resonant photoemission spectroscopy (RPES) measurements of Mn-implanted 3$C$-SiC (3$C$-SiC:Mn) and carbon-incorporated Mn$_{5}$Si$_{2}$ (Mn$_{5}$Si$_{2}$:C). The Mn 2$p$ core-level XPS and XAS spectra of 3$C$-SiC:Mn and Mn$_{5}$Si$_{2}$:C were similar to each other and showed "intermediate" behaviors between the localized and itinerant Mn 3$d$ states. The intensity at the Fermi level was found to be suppressed in 3$C$-SiC:Mn compared with Mn$_{5}$Si$_{2}$:C. These observations are consistent with the formation of Mn$_{5}$Si$_{2}$:C clusters in the 3$C$-SiC host, as observed in a recent transmission electron microscopy study., Comment: 4 pages, 3 figures

The electronic structure of the Cr ions in Zn1−x Cr x Te (x=0.03 and 0.15) has been investigated using X-ray magnetic circular dichroism (XMCD) and photoemission spectroscopy. Magnetic-field (H) and temperature (T) dependences of the Cr L 2,3 XMCD spectra well corresponded to the behavior of the magnetization measured by a SQUID magnetometer. The line shape of the Cr L 2,3 XMCD spectra was independent of H,T, and x, indicating that the ferromagnetism was originated from the same Cr electronic states independent of Cr concentration. The Cr 3d partial density of states (DOS) showed a peak at the top of the valence band but there was no DOS at the Fermi level, corresponding to their insulating behaviors.

The electronic structures of the ferromagnetic superconductors ${\mathrm{UGe}}_{2}$ and $\mathrm{UCoGe}$ in the paramagnetic phase were studied by angle-resolved photoelectron spectroscopy using soft x rays $(h\ensuremath{\nu}=400\text{--}500\phantom{\rule{0.28em}{0ex}}\mathrm{eV})$. The quasiparticle bands with large contributions from $\mathrm{U}\phantom{\rule{0.28em}{0ex}}5f$ states were observed in the vicinity of ${E}_{\mathrm{F}}$, suggesting that the $\mathrm{U}\phantom{\rule{0.28em}{0ex}}5f$ electrons of these compounds have an itinerant character. Their overall band structures were explained by the band-structure calculations treating all the $\mathrm{U}\phantom{\rule{0.28em}{0ex}}5f$ electrons as being itinerant. Meanwhile, the states in the vicinity of ${E}_{\mathrm{F}}$ show considerable deviations from the results of band-structure calculations, suggesting that the shapes of Fermi surface of these compounds are qualitatively different from the calculations, possibly caused by electron correlation effect in the complicated band structures of the low-symmetry crystals. Strong hybridization between $\mathrm{U}\phantom{\rule{0.28em}{0ex}}5f$ and $\mathrm{Co}\phantom{\rule{0.28em}{0ex}}3d$ states in $\mathrm{UCoGe}$ were found by the $\mathrm{Co}\phantom{\rule{0.28em}{0ex}}2p\ensuremath{-}3d$ resonant photoemission experiment, suggesting that $\mathrm{Co}\phantom{\rule{0.28em}{0ex}}3d$ states have finite contributions to the magnetic, transport, and superconducting properties.

The temperature evolution of the electronic structure of a Ni-Fe(Co)-Ga/MgO(100), Heusler-type, ferromagnetic shape-memory alloy thin film has been followed by a bulk-sensitive hard x-ray photoelectron spectroscopy, element-selective soft x-ray magnetic circular dichroism, and first-principles calculation. The reversible changes of the electronic states near the Fermi energy show a hysteresis associated with the martensitic phase transition (MPT), where the pseudogap opens on cooling and closes again on warming. In addition, the Ni $3d$ spin magnetic moment increases by approximately two times across the MPT, whereas the change of Fe $3d$ moment is moderate. By comparing the experimental results with the calculated spin-resolved density of states, we conclude that the band Jahn-Teller effect of Ni $3d$ and Fe $3d$ orbitals is responsible for MPT.

Thin films of the ferromagnetic metal SrRuO3 (SRO) show a varying easy magnetization axis depending on the epitaxial strain and undergo a metal-to-insulator transition with decreasing film thickness. We have investigated the magnetic properties of SRO thin films with varying thicknesses fabricated on SrTiO3(001) substrates by soft x-ray magnetic circular dichroism (XMCD) at the Ru M2,3 edge. Results have shown that, with decreasing film thickness, the film changes from ferromagnetic to non-magnetic around 3monolayer thickness, consistent with previous magnetization and magneto-optical Kerr effect measurements. The orbital magnetic moment perpendicular to the film was found to be ~ 0.1{\mu}B/Ru atom, and remained nearly unchanged with decreasing film thickness while the spin magnetic moment decreases. Mechanism for the formation of the orbital magnetic moment is discussed based on the electronic structure of the compressively strained SRO film., Comment: 6 pages, 6 figures, Submitted in Phys. Rev. B

We report on a microscopic study of the evolution of ferromagnetism in the Ru substituted ferromagnetic superconductor FM SC UCoGe crystallizing in the orthorhombic TiNiSi type structure. For that purpose, two single crystals with composition UCo0.97Ru0.03Ge and UCo0.88Ru0.12Ge have been prepared and characterized by magnetization, AC susceptibility, specific heat and electrical resistivity measurements. Both compounds have been found to order ferromagnetically below TC 6.5 and 7.5 K, respectively, which is considerably higher than the TC 3 K of the parent compound UCoGe. The higher values of TC are accompanied by enhanced values of the spontaneous moment amp; 956;spont 0.11 amp; 956;B f.u. and amp; 956;spont 0.21 amp; 956;B f.u., respectively in comparison to the tiny spontaneous moment of UCoGe about 0.07 amp; 956;B f.u. . No sign of superconductivity was detected in either compound. The magnetic moments of the samples were investigated on the microscopic scale using polarized neutron diffraction PND and for UCo0.88Ru0.12Ge also by soft X ray magnetic circular dichroism XMCD . The analysis of the PND results indicates that the observed enhancement of ferromagnetism is mainly due to the growth of the orbital part of the uranium 5f moment amp; 956;UL, reflecting a gradual localization of the 5f electrons with Ru substitution. In addition, the parallel orientation of the U and Co moments has been established in both substituted compounds. The results are discussed and compared with related isostructural ferromagnetic UTX compounds T transition metals, X Si, Ge in the context of a varying degree of the 5f ligand hybridization

We have investigated the electronic structure of Cr- and Mn-doped GaN using photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS). Cr and Mn XAS at the L-edge have indicated that the Cr and Mn ions are in the tetrahedral crystal field and that their valences are trivalent and divalent, respectively. Upon Cr and Mn doping into GaN, new states were found to form in the band-gap region of GaN. Resonant photoemission spectroscopy (RPES) has revealed that the main structure of the Cr 3d partial density of states (PDOS) appears within the band gap of GaN while that of the Mn 3d PDOS appears within the valence band of GaN and as a shoulder above the valence-band maximum of GaN, indicating that the character of the doping-induced states is different between Ga 1-x Cr x N and Ga 1-x Mn x N.