Spin and Orbital Magnetic Moments of Fe_{3}O_{4}

Huang, Di‐Jing; Chang, C. F.; Jeng, Horng‐Tay; Guo, Guang‐Yu; Lin, Hong Ji; Wu, Wen Bin; Ku, H. C.; Fujimori, A.; Takahashi, Yoshinori; Chen, C. T.

doi:10.1103/physrevlett.93.077204

Cited by 169 publications

(102 citation statements)

References 40 publications

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“…Figure 3 shows XAS and XMCD data for (a,d)  = 0, (b,e)  = 0.2 and (c,f)  = 0.2 at the Fe and Co L2,3 edges respectively. Three peaks are present in the XMCD spectra, similar to that found for Fe3O4 [19]. These peaks correspond to contributions from Fe 3+ in octahedral, Fe 3+ in tetrahedral and Fe 2+ in octahedral sites.…”

Section: Resultsmentioning

confidence: 49%

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Beevers

Love

Lazarov

et al. 2018

Applied Physics Letters

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Article:Beevers, J. E., Love, C. J., Lazarov, V. K. orcid.org/0000-0002-4314-6865 et al. The magnetoelectric effect in M-type Ti-Co doped strontium hexaferrite has been studied using a combination of magnetometry and element specific soft X-ray spectroscopies. A large increase (> x30) in the magnetoelectric coefficient is found when Co 2+ enters the trigonal bi-pyramidal site. The 5-fold trigonal bi-pyramidal site has been shown to provide an unusual mechanism for electric polarization based on the displacement of magnetic transition metal (TM) ions. For Co entering this site, an offcentre displacement of the cation may induce a large local electric dipole as well as providing an increased magnetostriction enhancing the magnetoelectric effect. INTRODUCTIONThe control of magnetism using applied electric fields offer the possibility of a new generation of ultralow power, high density storage. In this respect, magnetoelectric (ME) multiferroic materials are intensely studied in order to understand how different symmetry breaking orders exist in the same material and how these orders can be coupled. Among the few room temperature single-phase ME multiferroics reported, hexaferrites show potential for device applications as they exhibit a low field ME effect at room temperature [1]. M-type hexaferrites are arranged in different repeating sequences of basic building blocks; the R and S layers [2]. Fe 3+ cations occupy both octahedral (Oh) and tetrahedral (Td) co-ordinated sites in the S block (Wyckoff positions 2a and 4f1) and octahedral sites (12k and 4f2) in the R block, see online supplementary materials. The Ba ion located at positions 2d strongly distorts the octahedral site located at the 2b positions giving rise to a bi-pyramidal 5 fold co-ordination which induces a large uniaxial magnetic anisotropy parallel to the c-axis [3]. However, Co 2+ and Ti 4+ substitutions for Fe 3+ dramatically alters the magnetic properties [4]. Ti substitutions at the 12k sites decrease the exchange coupling between spins in the R and S blocks whilst Co substitutions change the magnetic anisotropy from uniaxial to an easy cone of magnetization tilted away from the c-axis. The result is to stabilize a non-collinear conical magnetic structure [2,5] which is of high interest in the field of multiferroics [6]. The ME effect at room temperature in SrFe8Ti2Co2O19 was first reported in bulk [7] and, thereafter, in thin films [8]. Co 2+ substitutions in ferrite structures are a well-known source of magnetoelastic coupling due to the large orbital moment of Co 2+ [9]. The linear ME coupling, , which is the change in magnetization with an applied electric field is directly proportional to the magnetoelastic coupling, or magnetostriction, , implying that an increase in  increases  [10]. However, a mechanism such as the piezoelectric effect or electrostriction for coupling the applied electric field into strain is also required. Several mechanisms for magnetically induced ferroelectricity have been proposed in recent years [11] with the sp...

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Section: Resultsmentioning

confidence: 49%

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Beevers

Love

Lazarov

et al. 2018

Applied Physics Letters

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“…It must be noted, however, that the energies depend on the termination, and that the Fe tet termination of (001) considered does not appear to form on the basis of experimental work. Yang et al [197], on the other hand, find that the (111) surface is less favourable than the (110) and (100) in their DFT+U calculations, and should be kinetically hindered. α-Fe 2 O 3 particles grown in hydrothermal conditions are found to be either rhombohedral, plate-like or rounded [199; 200].…”

Section: Photoelectrochemical Water Splittingmentioning

confidence: 99%

Iron oxide surfaces

Parkinson

2016

Surface Science Reports

482

463

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The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), hematite (α-Fe 2 O 3 ), and wüstite (Fe 1-x O) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe 3 O 4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment, and because it is an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed.The best understood iron oxide surface at present is probably Fe 3 O 4 (100); the structure is known with a high degree of precision and the major defects and properties are well characterised. A major factor in this is that a termination at the Fe oct -O plane can be reproducibly prepared by a variety of methods, as long as the surface is annealed in 10 Such straightforward preparation of a monophase termination is generally not the case for other iron oxide surfaces. All available evidence suggests the oft-studied (√2×√2)R45° reconstruction results from a rearrangement of the cation lattice in the outermost unit cell in which two octahedral cations are replaced by one tetrahedral interstitial, a motif conceptually similar to well-known Koch-Cohen defects in Fe (0001) is the most studied hematite surface, but 2 difficulties preparing stoichiometric surfaces under UHV conditions have hampered a definitive determination of the structure. There is evidence for at least three terminations: a bulk-like termination at the oxygen plane, a termination with half of the cation layer, and a termination with ferryl groups. When the surface is reduced the so-called "bi-phase" structure is formed, which eventually transforms to a Fe 3 O 4 (111)-like termination. The structure of the bi-phase surface is controversial; a largely accepted model of coexisting Fe 1-x O and α-Fe 2 O 3 (0001) islands was recently challenged and a new structure based on a thin film of Fe 3 O 4 (111) on α-Fe 2 O 3 (0001) was proposed. The merits of the compet...

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“…The XAS spectra were obtained by total electron yield (TEY) detection. The XMCD was taken as the difference of the XAS spectra, i.e., σ --σ + , obtained by flipping the X-ray helicity at a fixed magnetic field of 30 …”

Section: Xmcd Measurementmentioning

confidence: 99%

“…30 In order to rule out non-magnetic parts of the XAS spectra an arctangent based step function is used to fit the threshold. 26 As can be seen from up and data analysis of XMCD of magnetite were discussed in detail by Goering et al.…”

Section: Xmcd Measurementmentioning

confidence: 99%

“…The presence of integer m spin and vanishing orbital moment (m orb ) of magnetite are expected as an indication for a B-site minority electron conduction mechanism, and its accompanied full spin polarization at the E F . However, concerning with that, controversial results have been reported utilizing techniques such superconducting quantum interference device (SQUID) magnetometer, 11,38 XMCD, 12,27,30,39,38 and magnetic Compton scattering (MCS) 33,34 and calculations with local density approximation (LDA), 30 LDA+U, 30 local spin density approximation (LSDA)+U, 2 and moment analysis etc.. 12 The fundamental magnetic properties of Fe 3 O 4 show strong dependence on the sample preparation methodology. By simultaneous oxidation, Babu et al 32 34 and all the way down to −0.001μ B /f.u.…”

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confidence: 99%

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X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100)

Liu

Song

Maltby

et al. 2015

Journal of Applied Physics

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Abstract:The spin and orbital magnetic moments of the Fe 3 O 4 epitaxial ultrathin film synthesized by plasma assisted simultaneous oxidization on MgO(100) have been studied with X-ray magnetic circular dichroism (XMCD). The ultrathin film retains a rather large total magnetic moment, i.e. (2.73±0.15)μ B /f.u., which is ~ 70% of that for the bulk-like Fe 3 O 4 . A significant unquenched orbital moment up to (0.54±0.05) μ B /f.u. was observed, which could come from the symmetry breaking at the Fe 3 O 4 /MgO interface. Such sizable orbital moment will add capacities to the Fe 3 O 4 -based spintronics devices in the magnetization reversal by the electric field.

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Spin and Orbital Magnetic Moments of Fe_{3}O_{4}

Cited by 169 publications

References 40 publications

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Iron oxide surfaces

X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100)

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