Showing papers on "Magnetic structure published in 2006"
IBM1
TL;DR: This work used a scanning tunneling microscope to probe the interactions between spins in individual atomic-scale magnetic structures and observed excitations of the coupled atomic spins that can change both the total spin and its orientation.
Abstract: We used a scanning tunneling microscope to probe the interactions between spins in individual atomic-scale magnetic structures. Linear chains of 1 to 10 manganese atoms were assembled one atom at a time on a thin insulating layer, and the spin excitation spectra of these structures were measured with inelastic electron tunneling spectroscopy. We observed excitations of the coupled atomic spins that can change both the total spin and its orientation. Comparison with a model spin-interaction Hamiltonian yielded the collective spin configuration and the strength of the coupling between the atomic spins.
609 citations
TL;DR: In this article, it was shown that in the phase with an incommensurate magnetic structure of the manganese spins, the magneto-dielectric coupling can be suppressed and the electromagnons wiped out, thereby inducing considerable changes in the index of refraction from d.c.to terahertz frequencies.
Abstract: Magnetodielectric materials are characterized by a strong coupling of the magnetic and dielectric properties and, in rare cases, simultaneously show both magnetic and polar order. Among other multiferroics, TbMnO3 and GdMnO3 reveal a strong magneto–dielectric coupling and as a consequence fundamentally different spin excitations exist: electro-active magnons (or electromagnons), spin waves that can be excited by a.c. electric fields. Here we provide evidence that these excitations appear in the phase with an incommensurate magnetic structure of the manganese spins. In external magnetic fields this incommensurate structure can be suppressed and the electromagnons wiped out, thereby inducing considerable changes in the index of refraction from d.c. up to terahertz frequencies. Hence, besides adding a creature to the zoo of fundamental excitations, the refractive index can be tuned by moderate magnetic fields, which enables the design of the next generation of optical switches and optoelectronic devices.
398 citations
TL;DR: In this article, the authors reported the discovery of a medium-strength magnetic field on the young, massive star tauSco (B0.2V), which becomes the third-hottest magnetic star known.
Abstract: We report the discovery of a medium-strength (~0.5kG) magnetic field on the young, massive star tauSco (B0.2V), which becomes the third-hottest magnetic star known. Circularly polarized Zeeman signatures are clearly detected in observations collected mostly with the ESPaDOnS spectropolarimeter, recently installed on the 3.6-m Canada-France-Hawaii Telescope; temporal variability is also clearly established in the polarimetry, and can be unambiguously attributed to rotational modulation with a period close to 41d. Archival UV spectra confirm that this modulation repeats over timescales of decades.
By reconstructing the large-scale structure of its magnetic topology, we find that the magnetic structure is unusually complex for a hot star. The surface topology is dominated by a potential field, although a moderate toroidal component is probably present. We fail to detect intrinsic temporal variability of the magnetic structure over the 1.5-yr period of our spectropolarimetric observations (in agreement with the stable temporal variations of the UV spectra), and infer that any differential surface rotation must be very small.
The topology of the extended magnetic field that we derive from the photospheric magnetic maps is also more complex than a global dipole, and features in particular a significantly warped torus of closed magnetic loops encircling the star (tilted at about 90deg to the rotation axis), with additional, smaller, networks of closed field lines. This topology appears to be consistent with the exceptional Xray properties of tauSco and also provides a natural explanation of the variability observed in wind-formed UV lines. We conclude that its magnetic field is most probably a fossil remnant from the star-formation stage.
397 citations
TL;DR: This result demonstrates that an electric polarization flop can be induced by a magnetic field in a simple system without rare-earth 4f moments.
Abstract: The relationship between magnetic order and ferroelectric properties has been investigated for MnWO4 with a long-wavelength magnetic structure. Spontaneous electric polarization is observed in an elliptical spiral spin phase. The magnetic-field dependence of electric polarization indicates that the noncollinear spin configuration plays a key role for the appearance of the ferroelectric phase. An electric polarization flop from the b direction to the a direction has been observed when a magnetic field above 10 T is applied along the b axis. This result demonstrates that an electric polarization flop can be induced by a magnetic field in a simple system without rare-earth 4f moments.
320 citations
TL;DR: In this article, the authors studied the electron-boson interaction energies at the nanometre scale in high-Tc superconductor Bi2Sr2CaCu2O8+δ and found that the mode energies are always spatially anticorrelated with the superconducting pairing-gap energies, suggesting that the bosonic modes are unrelated to electronic or magnetic structure.
Abstract: Formation of electron pairs is essential to superconductivity. For conventional superconductors, tunnelling spectroscopy has established that pairing is mediated by bosonic modes (phonons); a peak in the second derivative of tunnel current d2I/dV2 corresponds to each phonon mode1,2,3. For high-transition-temperature (high-Tc) superconductivity, however, no boson mediating electron pairing has been identified. One explanation could be that electron pair formation4 and related electron–boson interactions are heterogeneous at the atomic scale and therefore challenging to characterize. However, with the latest advances in d2I/dV2 spectroscopy using scanning tunnelling microscopy, it has become possible to study bosonic modes directly at the atomic scale5. Here we report d2I/dV2 imaging6,7,8 studies of the high-Tc superconductor Bi2Sr2CaCu2O8+δ. We find intense disorder of electron–boson interaction energies at the nanometre scale, along with the expected modulations in d2I/dV2 (refs 9, 10). Changing the density of holes has minimal effects on both the average mode energies and the modulations, indicating that the bosonic modes are unrelated to electronic or magnetic structure. Instead, the modes appear to be local lattice vibrations, as substitution of 18O for 16O throughout the material reduces the average mode energy by approximately 6 per cent—the expected effect of this isotope substitution on lattice vibration frequencies5. Significantly, the mode energies are always spatially anticorrelated with the superconducting pairing-gap energies, suggesting an interplay between these lattice vibration modes and the superconductivity.
311 citations
TL;DR: In this article, the bulk properties of the quaternary Heusler alloy Co2Mn1�xFexSi with the Fe concentration x = 0,1/2,1 were investigated by means of x-ray diffraction, high-temperature magnetometry, Mossbauer spectroscopy, and differential scanning calorimetry.
Abstract: This paper reports on the bulk properties of the quaternary Heusler alloy Co2Mn1�xFexSi with the Fe concentration x =0,1/2,1. All samples, which were prepared by arc melting, exhibit L21 long-range order over the complete range of Fe concentration. The structural and magnetic properties of the Co2Mn1�xFexSi Heusler alloys were investigated by means of x-ray diffraction, high- and low-temperature magnetometry, Mossbauer spectroscopy, and differential scanning calorimetry. The electronic structure was explored by means of highenergy photoemission spectroscopy at about 8 keV photon energy. This ensures true bulk sensitivity of the measurements. The magnetization of the Fe-doped Heusler alloys is in agreement with the values of the magnetic moments expected for a Slater-Pauling-like behavior of half-metallic ferromagnets. The experimental findings are discussed on the basis of self-consistent calculations of the electronic and magnetic structure. To achieve good agreement with experiment, the calculations indicate that on-site electron-electron correlation must be taken into account, even at low Fe concentration. The present investigation focuses on searching for the quaternary compound where the half-metallic behavior is stable against outside influences. Overall, the results suggest that the best candidate may be found at an iron concentration of about 50%.
261 citations
TL;DR: In this article, a review of the field of magnetically doped oxides and nitrides is presented from a materials science perspective, focusing on films prepared not only by conventional vacuum deposition methods, but also by spin coating colloidal nanoparticles in air.
228 citations
TL;DR: The magnetic moment of Co2FeSi was measured to be about 6μB at 5 K and the Curie temperature was measured with different methods to be (1100±20)K.
Abstract: Co2FeSi crystallizes in the ordered L21 structure as proven by x-ray diffraction and Moβbauer spectroscopy. The magnetic moment of Co2FeSi was measured to be about 6μB at 5 K. Magnetic circular dichroism spectra excited by soft x-rays were taken to determine the element-specific magnetic moments of Co and Fe. The Curie temperature was measured with different methods to be (1100±20)K. Co2FeSi was found to be the Heusler compound as well as the half-metallic ferromagnet with the highest magnetic moment and Curie temperature.
168 citations
TL;DR: A model is proposed, based on a simple magnetoelastic coupling to the lattice, which enables the polarization based entirely on the observed magnetic structure to be predicted, and accurately reproduce the temperature dependence of the spontaneous polarization.
Abstract: The commensurate and incommensurate magnetic structures of the magnetoelectric system YMn2O5, as determined from neutron diffraction, were found to be spin-density waves lacking a global center of symmetry. We propose a model, based on a simple magnetoelastic coupling to the lattice, which enables us to predict the polarization based entirely on the observed magnetic structure. Our data accurately reproduce the temperature dependence of the spontaneous polarization, particularly its sign reversal at the commensurate-incommensurate transition.
150 citations
TL;DR: In this paper, the electronic and magnetic properties of Mn2V-based full Heusler alloys were studied and it was shown that a small expansion of the calculated theoretical equilibrium lattice constants restores the half-metallic ferrimagnetism in these compounds.
Abstract: Using a state-of-the-art full-potential electronic structure method within the local spin density approximation, we study the electronic and magnetic structure of Mn2V-based full Heusler alloys: Mn2VZ (Z = Al, Ga, In, Si, Ge and Sn). We show that small expansion of the calculated theoretical equilibrium lattice constants restores the half-metallic ferrimagnetism in these compounds. Moreover, a small degree of disorder between the V and Z atoms, although it induces some states within the gap, preserves the Slater–Pauling behaviour of the spin magnetic moments and the alloys keep a high degree of spin polarization at the Fermi level, opening the way for a half-metallic compensated ferrimagnet.
145 citations
TL;DR: In this paper, the Kohn-Sham equations were solved by applying the full-potential linearized augmented plane wave method, and the generalized gradient approximation in the Perdew-Wang formalism was used to the exchange and correlation energy functional.
Abstract: First principle calculations have been performed to study the crystalline, electronic, and magnetic structures of three iron-carbide systems: θ-Fe3C, χ-Fe5C2, and η-Fe2C. The Kohn-Sham equations were solved by applying the full-potential linearized augmented plane wave method. The generalized gradient approximation in the Perdew-Wang formalism was used to the exchange and correlation energy functional. The internal positions of atoms within the unit cell were optimized and the ground state properties such as lattice parameter and bulk modulus were calculated. The results are compared with experimental data when available. Comparison of the two metastable systems χ-Fe5C2 and η-Fe2C shows that the last one has lower formation energy; this is corroborated by the formation sequence observed during tempering. The electronic structures of the three carbides were then studied and the magnetic moments calculated by means of electronic spin-resolved density of state calculations at their equilibrium lattice consta...
TL;DR: In this article, the multiferroic behavior of MnWO4, a magnetic oxide with monoclinic crystal structure and spiral long-range magnetic order, was investigated.
Abstract: We report the multiferroic behaviour of MnWO4, a magnetic oxide with monoclinic crystal structure and spiral long-range magnetic order. Based upon recent theoretical predictions, MnWO4 should exhibit ferroelectric polarization coexisting with the spiral magnetic structure. We have confirmed the multiferroic state below 13 K by observing a finite electrical polarization in the magnetically ordered state via pyroelectric current measurements.
TL;DR: In this article, the structural, the composition and chemical state of the surface and magnetic properties of different nanosized CuFe 2 O 4 powders exhibiting collective Jahn-Teller effect were compared.
TL;DR: In this paper, the multiferroic behavior of MnWO$_4$, a magnetic oxide with monoclinic crystal structure and spiral long-range magnetic order, was investigated.
Abstract: We report the multiferroic behaviour of MnWO$_4$, a magnetic oxide with monoclinic crystal structure and spiral long-range magnetic order. Based upon recent theoretical predictions MnWO$_4$ should exhibit ferroelectric polarization coexisting with the proper magnetic structure. We have confirmed the multiferroic state below 13 K by observing a finite electrical polarization in the magnetically ordered state via pyroelectric current measurements.
TL;DR: YBaCo{sub 4}O{sub 7} belongs to a new class of geometrically frustrated magnets like the pyrochlores, in which Co spins occupy corners of tetrahedra as mentioned in this paper.
Abstract: YBaCo{sub 4}O{sub 7} belongs to a new class of geometrically frustrated magnets like the pyrochlores, in which Co spins occupy corners of tetrahedra. The structure can be viewed as an alternating stacking of Kagome and triangular layers. Exactly half of the triangular units of the Kagome plane are capped by Co ions to form columns running perpendicular to the Kagome sheets. Neutron powder diffraction reveals a broad temperature range of diffuse magnetic scattering, followed by long-range magnetic ordering below 110 K. A unique low-temperature magnetic structure simultaneously satisfies an S=0 arrangement in the uncapped triangular units and antiferromagnetic coupling along the columns. A spin reorientation above 30 K tracks the relative strengths of the in-plane and out-of-plane interactions.
TL;DR: In this paper, the electronic and magnetic structure of the low-temperature phase of ScMnO3 was studied theoretically from first principles, and the solid phase was modeled with periodic supercells using three different methods: unrestricted Hartree-Fock, B3LYP and BLYP.
Abstract: The electronic and magnetic structure of the low-temperature phase of ScMnO3 was studied theoretically from first principles The solid phase was modeled with periodic supercells using three different methods: unrestricted Hartree–Fock, B3LYP and BLYP The magnetic coupling constants obtained with these methods were compared with experimental values The effect of lattice relaxation on the coupling constant was investigated (© 2006 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim)
TL;DR: It is demonstrated that the complex magnetic structure observed is induced by the strong Fe-Ir hybridization, which is lower in energy than all solutions of the classical Heisenberg model.
Abstract: We have observed a novel magnetic structure in the pseudomorphic Fe monolayer on Ir(111). Using spin-polarized scanning tunneling microscopy we find a nanometer-sized two-dimensional magnetic unit cell. A collinear magnetic structure is proposed consisting of 15 Fe atoms per unit cell with 7 magnetic moments pointing in one and 8 moments in the opposite direction. First-principles calculations verify that such an unusual magnetic state is indeed lower in energy than all solutions of the classical Heisenberg model. We demonstrate that the complex magnetic structure is induced by the strong Fe-Ir hybridization.
TL;DR: This work has synthesized, for the first time, highly spin polarized complex magnetic oxide nanostructures embedded in a paramagnetic matrix by electron beam lithography and ion implantation.
Abstract: The realization of spin-based devices requires high density, ordered arrays of magnetic materials with a high degree of spin polarization at surfaces. We have synthesized, for the first time, highly spin polarized complex magnetic oxide nanostructures embedded in a paramagnetic matrix by electron beam lithography and ion implantation. Imaging the magnetic domains with X-ray photoemission electron microscopy and magnetic force microscopy reveals a delicate balance between magnetocrystalline, magnetoelastic, and magnetostatic energies that can be tuned by the choice of SrTiO3 substrate orientation, film thickness, island size, and island shape.
TL;DR: In this paper, a review of the presently available knowledge about epitaxial growth of MnAs films in a variety of orientations on differently oriented GaAs substrates, their interface formation, and the interrelated structural and magnetic properties is presented.
Abstract: Studies on MnAs, and in particular of its magnetostructural phase transition, have a long history. As a promising material for ferromagnet/semiconductor hybrid structures with new challenges for solid state physics and electronic engineering, MnAs thin films recently came again into the focus of interest. This review summarizes the presently available knowledge about epitaxial growth of MnAs films in a variety of epitaxial orientations on differently oriented GaAs substrates, their interface formation, and the interrelated structural and magnetic properties. In situ growth studies using reflection-high energy electron diffraction and high-resolution x-ray diffraction as well as imaging of the growth morphology by scanning tunnelling microscopy provided a detailed understanding of the growth kinetics. The mismatch accommodation mechanisms elucidated by high-resolution transmission electron microscopy investigations explain how films of high quality can be grown despite a large and anisotropic misfit. Most extensively considered are structural and magnetic properties that are related to the strain evolution in the films during cooling after growth. In clear contrast to bulk MnAs, the structural phase transition in MnAs films exhibits a coexistence of the ferromagnetic ?-phase and the paramagnetic ?-phase over a wide range of temperatures and a thickness dependent thermal hysteresis. This strain-mediated phase coexistence has been studied in detail by x-ray diffraction and by imaging the magnetic structure using magnetic force microscopy and magnetic circular dichroism photoemission electron microscopy, and also theoretically. It depends in a characteristic manner on the epitaxial orientation. Using high-resolution x-ray diffraction data, it is shown that a unified mechanism explains the shift of the ferromagnetic transition temperature to higher values in as-grown MnAs films of appropriate epitaxial orientation, in MnAs films under external biaxial strain, and in MnAs clusters within a GaAs matrix. The improvement of the structural and magnetic properties of the films by a post-growth thermal annealing process is demonstrated.
TL;DR: In this article, the substitution effect of Sr2+ for Ba2+ on the crystal structures and the effective sizes and directions of magnetic moments and their temperature dependences with high-temperature neutron diffraction technique.
Abstract: We have prepared nonoriented and magnetically oriented specimens of Co2Z-type Ba ferrite Ba3Co2Fe24O41 (Ba3Z) and those with Sr2+ substitution for Ba2+, i.e., Ba1.5Sr1.5Co2Fe24O41 (Ba1.5Sr1.5Z) and Sr3Co2Fe24O41 (Sr3Z) with the conventional solid-state reaction method. Permeability measurements of nonoriented specimens have shown that this substitution improves the frequency characteristic of permeability, though the permeability in Sr3Z significantly decreases. X-ray diffraction (XRD) and magnetization measurements of magnetically oriented specimens have shown that the magnetic moments of iron and cobalt ions in Ba3Z and Ba1.5Sr1.5Z lie in the c plane, but that those in Sr3Z deviate from the c plane. We have studied the substitution effect of Sr2+ for Ba2+ on the crystal structures and the effective sizes and directions of magnetic moments and their temperature dependences with high-temperature neutron diffraction technique. This substitution induces the change in the distribution of cobalt ions and mome...
TL;DR: In this paper, a new study of the magnetic and crystalline structures of YMnO3 and HoNO3 using neutron diffraction combined with neutron polarimetry was conducted.
Abstract: We have undertaken a new study of the magnetic and crystalline structures of YMnO3 and HoMnO3 using neutron diffraction combined with neutron polarimetry It is shown how the long-standing problem of distinguishing between magnetic structure models which give nearly identical diffraction intensities may be resolved The experiments show that the magnetic structure of YMnO3 has space group P63' (or P63) rather than P63'cm' (or P63cm) with Mn moments of 314(3) μB inclined at 11(1)° to [100] (or [120] for P63) in the (001) plane For HoMnO3 the experiments confirm the P63'c'm symmetry at 50 K and the spin-rotation transition leading to a low-temperature structure with magnetic space group P63'cm' In this structure both the Ho1 and Ho2 moments can order with spins parallel to [001] in ferromagnetic layers, anti-ferromagnetically coupled The Ho1 and Ho2 moments in neighbouring layers are found to be oppositely oriented The ordered moments at 2 K are 332(8), 417(13) and 131(11) μB on the Mn, Ho1 and Ho2 atoms respectively No evidence was found, in this zero-field study, for the magnetic transition at ≈5 K reported in the literature (Lottermoser et al 2004 Nature 30 541; Vajk et al 2005 Phys Rev Lett 94 87601) Nuclear structure refinements show that in YMnO3 at 10 K and in HoMnO3 at all temperatures below 50 K any deviation of the manganese x parameter from 1/3 is less than 00008
TL;DR: In this article, the effect of a high axial magnetic field on the microstructure in a directionally solidified Al-Al2Cu eutectic alloy has been investigated experimentally.
TL;DR: Total neutron scattering data from a powdered sample of MnO collected at 10 K have been analyzed using the reverse Monte Carlo method to refine the nuclear and magnetic structure and give the first unambiguous assignment of the average magnetic structure.
Abstract: Total neutron scattering data from a powdered sample of MnO collected at 10 K have been analyzed using the reverse Monte Carlo method to refine the nuclear and magnetic structure. The results give the first unambiguous assignment of the average magnetic structure. The magnetic moments are aligned ferromagnetically within (111) sheets with the magnetization vectors of alternate sheets along axes parallel and antiparallel to the directions, albeit with a small modulated out-of-plane component. Small displacements of Mn and O (modulated with the same periodicity) accompany the magnetic ordering and both atomic and magnetic structures may be described in the monoclinic space group C2.
TL;DR: In this article, the properties of polycrystalline samples of Gd 3 Co and gd 3 Ni have been studied and it was found that Gd3 Ni possesses larger magnetic anisotropy compared to Gd 2 Co.
TL;DR: The perovskite polymorph of YbMnO3 has been revisited in this article, where the orthorhombic phase is obtained through a high pressure reconstructive transformation from the hexagonal sol−gel-synthesized YbNO3 by means of HP annealing.
Abstract: The perovskite polymorph of YbMnO3 has been revisited. The orthorhombic phase is obtained through a high-pressure (HP) reconstructive transformation from the hexagonal sol−gel-synthesized YbMnO3 by means of HP annealing at 5 GPa and 1100 °C. Neutron powder diffraction shows that the HP form crystallizes in the orthorhombic space group Pbnm. At 298 K, the refined values for lattice parameters a, b, and c are respectively 5.2208(3), 5.8033(3), and 7.3053(4) A. The average Mn−O−Mn angle is 141.9°, indicative of a strong tilting of the MnO6 octahedra. Magnetic susceptibility measurements indicate antiferromagnetic order of Mn3+ spins at TN = 43 K and of Yb3+ spins at 4 K. The magnetic structure is commensurate Ay with an ordered moment 3.45(5) μB at 9 K. The magnetic susceptibility obeys the Curie−Weiss law, χ = C/(T − θ), in two temperature regions, that is, above 240 K and 6−30 K. The obtained effective paramagnetic moments μeff are 6.37 μB and 4.83 μB for the two temperature ranges, respectively. The forme...
TL;DR: In this paper, the Stokes profiles of magnetic dipole (M1) emission lines produced in current-carrying magnetic structures were analyzed. But the results were limited to the case of Fe xiii (1074.7 nm) and Si x (1430.1 nm).
Abstract: We present the first theoretical, forward calculations of the Stokes profiles of several magnetic dipole (‘‘M1’’) coronal emission lines produced in current-carrying magnetic structures. An idealized coronal model of Low, Fong, and Fan is used, which describes a spherically symmetric, hydrostatic background atmosphere, isothermal at a coronal temperature of 1:6 ;10 6 K. Embedded is a global, axisymmetric magnetic field that is everywhere potential except at a quiescent prominence, consisting of an infinitesimally thin, equatorial current sheet whose weight is supported by the outward discrete Lorentz force in the sheet. This model contains a physically nontrivial, localized magnetic structure, although the atmospheric plasma is thermally of the simplest stratification possible. The calculated M1 coronal lines show clear and distinct signatures of the presence and magnitude of this localized magnetic structure, in both linear and circular polarizations, eventhough the thermal structure isalmost homogeneous. Themorphologyof mapsoflinearpolarizationisparticularlysensitive to the existenceand strengthofthe current sheets, asfield lines wrap around them according to the Biot-Savart law, and the linear polarization responds to different projections offield line directions onto local radius vectors. Of the M1 lines studied, those of Fe xiii (1074.7 nm) and Si x (1430.1 nm) are especiallypromisingbecauseoftheirrelativelystronglinearpolarization.Theseforwardcalculationsprovideabasisfor optimismthatemission-linemeasurementsmayrevealthepresenceandnatureofcurrentsystemsinthecorona,and provide motivation for developing instruments capable ofroutinely measuring polarized light in forbidden coronal lines.
TL;DR: In this article, it was suggested that the crystallographic structure of akaganeite is not tetragonal but monoclinic, thus another interpretation for the Mossbauer spectra is required.
Abstract: The Mossbauer spectra of akaganeite have always been interpreted considering both the tetragonal structure and the chlorine content. However, very recently it has been suggested that the crystallographic structure is not tetragonal but monoclinic, thus another interpretation for the Mossbauer spectra is required. For this purpose, we have prepared and characterized by several techniques synthetic akaganeite. Our results suggest that the two crystallographic sites required by the monoclinic symmetry are not distinguishable in the paramagnetic state as previously assumed, but they are only discernible in the low temperature magnetic region. At room temperature the spectrum is fitted with two doublets whose origin is related to the chlorine content, i.e. one Fe site assigned to Fe3+ ions located close to chloride ions and the other Fe site to those located close to chloride vacancy sites. The low temperature spectra can be adequately fitted with four sextets, whose hyperfine parameters must be subjected to some constraints. The origin of these components is related to the two different crystallographic sites and to the chlorine content. In-field Mossbauer spectrometry at low temperature suggests that the magnetic structure behaves as a system which consists of two asperimagnetic-like structures antiferromagnetically coupled, and not as a collinear antiferromagnet as usually assumed.
TL;DR: In this article, the effects of tetragonal strain on the electronic and magnetic properties of strontium-doped lanthanum manganite, La2/3Sr1/3MnO3 (LSMO), are investigated by means of density-functional methods.
Abstract: The effects of tetragonal strain on the electronic and magnetic properties of strontium-doped lanthanum manganite, La2/3Sr1/3MnO3 (LSMO), are investigated by means of density-functional methods. As far as the structural properties are concerned, the comparison between theory and experiments for LSMO strained on the most commonly used substrates shows an overall good agreement: the slight overestimate (at most of 1?1.5%) for the equilibrium out-of-plane lattice constants points to possible defects in real samples. The inclusion of a Hubbard-like contribution on the Mn d states, according to the so-called 'LSDA+U' approach, is rather ineffective from the structural point of view, but much more important from the electronic and magnetic point of view. In particular, full half-metallicity, which is missed within a bare density-functional approach, is recovered within LSDA+U, in agreement with experiments. Moreover, the half-metallic behaviour, particularly relevant for spin-injection purposes, is independent of the chosen substrate and is achieved for all the considered in-plane lattice constants. More generally, strain effects are not seen to crucially affect the electronic structure: within the considered tetragonalization range, the minority gap is only slightly (i.e.?by about 0.1?0.2?eV) affected by a tensile or compressive strain. Nevertheless, we show that the growth on a smaller in-plane lattice constant can stabilize the out-of-plane versus in-plane eg orbital and significantly change their relative occupancy. Since eg orbitals are key quantities for the double-exchange mechanism, strain effects are confirmed to be crucial for the resulting magnetic coupling.
TL;DR: In this paper, the magnetic properties and electronic structure of copper ferrites in both normal and inverse spinel structures were studied using a principle spin-polarized band structure calculation method with a modified Becke's three-parameter exchange correlation.
Abstract: Magnetic properties and electronic structure of copper ferrites in both normal and inverse spinel structures are studied using a principle spin-polarized band structure calculation method with a modified Becke’s three-parameter exchange correlation. The calculated exchange constants show that the Neel configuration may be unstable for both normal and inverse structures. The local magnetic moments are calculated using Mulliken population analysis and show that the normal structure may achieve very high magnetization. The calculated density of states show that copper ferrite in both normal and inverse spinel structure may be half metallic.
TL;DR: In this paper, the crystal and magnetic structures of SrRuO 3 were obtained by neutron diffraction and the ferromagnetically ordered Ru moment amounts to μ Ru = 1.63± 0.06 µ B at T = 10 K.