Mn 2p X-ray Absorption Spectroscopy Research Articles

XMCD and PES study of a compensated-ferrimagnetic half-metal Mn3Ga

By employing soft X-ray magnetic circular dichroism (XMCD), soft X-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES), we have investigated the electronic structure of the candidate zero-moment half-metallic Mn3Ga. We have studied the ball-milled and annealed Mn3Ga powder samples that exhibit nearly zero magnetization. Mn 2p XAS revealed that Mn ions in Mn3Ga are nearly divalent for both of the Mn ions having the locally octahedral symmetry and those having the locally tetrahedral symmetry. The measured Mn 2p XMCD spectrum of Mn3Ga is very similar to that of ferrimagnetic MnFe2O4 having divalent Mn ions. The sum-rule analysis of the Mn 2p XMCD spectrum shows that both the spin and orbital magnetic moments of Mn ions in Mn3Ga are negligibly small, in agreement with the nearly compensated-ferrimagnetic ground state of Mn3Ga. The valence-band PES spectrum of Mn3Ga agrees well with the calculated density of states, supporting the half-metallic electronic structure of Mn3Ga.

반쪽 금속 호이슬러 화합물 Mn3Ga의 연 X선 방사광 분광 연구

이 연구에서는 방사광을 이용한 연 X-선 흡수 분광법(soft X-ray absorption spectroscopy: XAS)과 광전자 분광법(photoemission spectroscopy: PES) 을 이용하여 반쪽금속 반강자성체 후보 물질인 <TEX>$Mn_3Ga$</TEX> 호이슬러 화합물의 전자구조를 연구하였다. 이 연구에 사용된 시료는 full-Heusler <TEX>$Mn_3Ga$</TEX>로 ball milling 후 열처리하지 않은 시료와 ball milling 후 <TEX>$400^{\circ}C$</TEX>에서 열처리한 두 시료를 사용하였다. XAS 분석에 의하면 <TEX>$Mn_3Ga$</TEX>에서 Mn 이온들의 원자가는 <TEX>$Mn^{2+}$</TEX> 상태임을 알 수 있었으며, 국소적으로 팔면체 대칭성을 가진 Mn 이온들과 사면체 대칭성을 가진 Mn 이온들이 섞여 있음을 알 수 있었다. 그리고 <TEX>$Mn_3Ga$</TEX>의 가전자띠 PES 스펙트럼은 전자구조 계산에 의한 반쪽 금속성 상태밀도와 대체로 유사함을 발견하였다. By employing photoemission spectroscopy (PES) and soft X-ray absorption spectroscopy (XAS), the electronic structure of the candidate half-metallic antiferromagnet of <TEX>$Mn_3Ga$</TEX> Heusler compound has been investigated. We have studied two ball-milled <TEX>$Mn_3Ga$</TEX> powder samples, one after annealing and the other without annealing, respectively. Based on the Mn 2p XAS study, we have found that Mn ions are nearly divalent in <TEX>$Mn_3Ga$</TEX> and that the Mn ions having the locally octahedral symmetry and those having the locally tetrahedral symmetry are both present in <TEX>$Mn_3Ga$</TEX>. We have found relatively good agreement between the measured valence-band PES spectrum of <TEX>$Mn_3Ga$</TEX> and the calculated density of states, which is in agreement with the half-metallic electronic structure of <TEX>$Mn_3Ga$</TEX>.

Soft x-ray synchrotron radiation spectroscopy study of SrMn1−xRuxO3 perovskites (≤x≤1)

The electronic structures of SrMn1−xRuxO3 (0≤x≤1) have been investigated by employing soft x-ray absorption spectroscopy (XAS). The measured Mn 2p XAS spectra for SrMn1−xRuxO3 show that the valence states of Mn ions change monotonically from Mn4+ for x=0 to ∼Mn3+ for x=0.8, suggesting that the valence states of the substituted Ru ions are higher than 4+. The Ru 3p XAS spectra of SrMn1−xRuxO3 show the existence of pentavalent Ru5+ ions for the low x value. The measured O 1s XAS spectra also support these findings.

Formation and Characterization of Manganese Silicide on Si(111) and Si(100) Substrates

The electronic structure of the interface formation at Mn/Si at room temperature (RT) and the growth of manganese silicide were studied by using photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS) with synchrotron radiation. The Mn coverage dependence of the Si 2p and the Mn 3p core-level spectra revealed that the growth of Mn on Si(111)-7 × 7 at RT started in a layer-by-layer growth at a coverage of less than 0.5 ML (monolayer). Mn 2p XAS spectra also showed no reaction between Mn and Si at RT. Three thin manganese silicide samples were prepared by using solid phase epitaxy at 610 ◦C (MSS), reactive deposition epitaxy at 290 ◦C for Si(111) and at 350 ◦C for Si(100) (MSR) and post annealing the MSR sample at 610 ◦C (MSP) on the Si(111) and the Si(100) substrates. The LOW ENERGY ELECTRON DIFFRACTION (LEED) pattern and the fine structure in the Mn 2p XAS spectra showed that the phases of the MSS, the MSR, and the MSP samples were the same. Emissions at the Fermi energy in the valence-band (VB) PES spectra and the line shape of Si 2p core-level photoemission spectra also showed the formation of metallic MnSi.

Synthesis and magnetic properties of MnSb nanoparticles on Si-based substrates

MnSb nanoparticles with average lateral diameters ⟨d⟩ from 5to30nm are synthesized on ultra thin silicon nitride covered Si(111) by codeposition of Mn and Sb. These MnSb particles possess sharp interfaces and a NiAs-type lattice. The Mn 2p x-ray absorption spectroscopy analysis shows broad line shapes due to the itinerant Mn 3d states. The particles with ⟨d⟩=5 and 8.5nm are superparamagnetic at room temperature, while those of ⟨d⟩=15 and 30nm exhibit ferromagnetic behavior.

Spatial Chemical Inhomogeneity and Local Electronic Structure of Mn-Doped Ge Ferromagnetic Semiconductors

We have investigated the chemical distributions and the local electronic structure of potential diluted magnetic semiconductor Ge0.94Mn0.06 single crystals using scanning photoelectron microscopy (SPEM), x-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES). The SPEM image shows the stripe-shaped microstructures, which arise from the chemical phase separation between the Mn-rich and Mn-depleted phases. The Mn 2p XAS shows that the Mn ions in the Mn-rich region are in the divalent high-spin Mn2+ states but that they do not form metallic Mn clusters. The Mn 3d PES spectrum exhibits a peak centered at approximately 4 eV below E(F) and the negligible spectral weight near E(F). This study suggests that the observed ferromagnetism in Ge1-xMnx arises from the phase-separated Mn-rich phase.

Electronic structure of La0.7Ce0.3MnO3 thin film

AbstractThe electronic structure of epitaxial thin films of La0.7Ce0.3MnO3 (LCeMO) has been investigated using photoemission spectroscopy (PES) and X‐ray absorption spectroscopy (XAS). The measured valence‐band PES, Ce 3d PES, and Ce 3d XAS spectra for LCeMO consistently indicate that the localized Ce 4f orbitals are almost unoccupied so that the Ce valence is nearly tetravalent. The Mn 2p XAS spectrum suggests Mn2+ and Mn3+ mixed‐valent states of Mn ions in LCeMO. The LSDA + U calculation agrees better with the measured PES/XAS spectra than the LSDA calculation (U: the on‐site Coulomb interaction). (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Photoemission and x-ray absorption spectroscopy study of electron-doped colossal magnetoresistive manganiteLa0.7Ce0.3MnO3films

The electronic structure of La0.7Ce0.3MnO3 (LCeMO) thin film has been investigated using photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). The Ce 3d core-level PES and XAS spectra of LCeMO are very similar to those of CeO2, indicating that Ce ions are far from being trivalent. A very weak 4f resonance is observed around the Ce 4d $\to$ 4f absorption edge, suggesting that the localized Ce 4f states are almost empty in the ground state. The Mn 2p XAS spectrum reveals the existence of the Mn(2+) multiplet feature, confirming the Mn(2+)-Mn(3+) mixed-valent states of Mn ions in LCeMO. The measured Mn 3d PES/XAS spectra for LCeMO agrees reasonably well with the calculated Mn 3d PDOS using the LSDA+U method. The LSDA+U calculation predicts a half-metallic ground state for LCeMO.

PES and XAS studies of Mn12-Ac molecular magnet

Abstract The electronic structure of Mn12-Ac has been investigated using photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The PES spectrum indicates that Mn 3d states are located near the top of the valence band, and the Mn 2p XAS spectrum provides clear evidence for the Mn3+–Mn4+ mixed-valent states.

Magnetic Properties of Mn Ultrathin Film on Ni(110)

Mn 3d electronic states of Mn ultrathin film grown on the surface of a Ni(110) single crystal at room temperature are studied by Mn 2p X-ray absorption spectroscopy (Mn 2p XAS) and magnetic circular dichroism (XMCD). From the Mn 2p XAS spectrum, it is found that Mn is in a high-spin state. The XMCD signal shows long-range magnetic ordering in the Mn submonolayer and its magnetic moment is parallel to that of the Ni substrate.

High-resolution photoemission spectroscopy for the layered antiferromagnetic (La(1-z)Nd(z))(0.46)Sr(0.54)MnO(3).

High-resolution HeI photoemission spectroscopy (UPS), Mn 2p-3d resonant photoemission spectroscopy (RPES) and Mn 2p X-ray absorption spectroscopy (XAS) have been performed to investigate the electronic structure and its effect on the electrical resistivity in (La(1-z)Nd(z))(0.46)Sr(0.54)MnO(3) (z = 0, 0, 2, 0.6 and 1.0). It was found that in the UPS and RPES spectra the Fermi edge persisted over the temperature range 15 < or = T < or = 340 K regardless of the magnetic structure or the composition of the samples. The density of states at the Fermi level [N(E(F))] in the samples where 0 < or = z < or = 0.6 was increased drastically at the Curie temperature (T(C)) with decreasing temperature, but essentially kept unchanged across the Néel temperature (T(N)). A fairly large reduction at T(C) and a small increase at T(N) in the electrical resistivity with decreasing temperature are found to be well accounted for in terms of the temperature dependence of N(E(F)). The presence of a finite N(E(F)) in the insulating Nd(0.46)Sr(0.54)MnO(3) was also found. Thus the origin of the insulating behavior in this sample can be regarded as the Anderson localization associated with the small density of states and the chemical disorder between Nd and Sr.