Showing papers on "Antiferromagnetism published in 2003"
TL;DR: A simple extension of the Meiklejohn and Bean model is proposed to account quantitatively for the exchange bias fields in the three studied systems from the experimentally determined number of pinned moments and their sizes.
Abstract: Using x-ray magnetic circular dichroism, we have detected the very interfacial spins that are responsible for the horizontal loop shift in three different exchange bias sandwiches, chosen because of their potential for device applications. The "pinned" uncompensated interfacial spins constitute only a fraction of a monolayer and do not rotate in an external magnetic field since they are tightly locked to the antiferromagnetic lattice. A simple extension of the Meiklejohn and Bean model is proposed to account quantitatively for the exchange bias fields in the three studied systems from the experimentally determined number of pinned moments and their sizes.
509 citations
TL;DR: The temperature-dependent magnetic response of exchange-coupled FePt/FeRh thin films is described in this article, where the FeRh layer is antiferromagnetic at room temperature but becomes ferromagnetic with a large magnetic moment and low magnetocrystalline anisotropy, forming an exchange-spring system and significantly lowering the coercive field of the composite system.
Abstract: The temperature-dependent magnetic response of exchange-coupled FePt/FeRh thin films is described. The FePt forms a high magnetocrystalline anisotropy, high-coercivity ferromagnetic layer. The FeRh layer is antiferromagnetic at room temperature but, upon heating above a transition temperature, becomes ferromagnetic with a large magnetic moment and low magnetocrystalline anisotropy, forming an exchange–spring system and significantly lowering the coercive field of the composite system. This feature opens intriguing possibilities for media applications for thermally assisted magnetic recording where the ferromagnetic phase of FeRh is exploited to help write the media while the antiferromagnetic phase supports the long-time stability.
422 citations
TL;DR: It is suggested that at optimal doping chiral spin fluctuations enhanced by the dopant dynamics lead to a gapful d-wave superconducting state.
Abstract: Takada et al. have reported superconductivity in layered Na(x)CoO(2)yH(2)O (T(c) approximately equal to 5 K). We model a reference neutral CoO2 layer as an orbitally nondegenerate spin-1/2 antiferromagnetic Mott insulator on a triangular lattice and Na(x)CoO(2)yH(2)O as electron doped Mott insulators described by a t-J model. It is suggested that at optimal doping chiral spin fluctuations enhanced by the dopant dynamics lead to a gapful d-wave superconducting state. A chiral resonating valence bond (RVB) metal, a parity and time (PT) reversal violating state with condensed RVB gauge fields, with a possible weak ferromagnetism, and low temperature p-wave superconductivity are also suggested at higher dopings.
234 citations
TL;DR: The large magnetocapacitance near the transition temperature in the ferromagnet SeCuO3 suggests routes to enhancing the magnetodielectric response for practical applications.
Abstract: We report on the effects of spin fluctuations, magnetic ordering, and external magnetic field on the dielectric constant of the ferromagnet SeCuO3, and the antiferromagnet TeCuO3. A model based on the coupling between uniform polarization and the q-dependent spin-spin correlation function is presented to explain the different behaviors for these isostructural compounds. The large magnetocapacitance near the transition temperature in the ferromagnet SeCuO3 suggests routes to enhancing the magnetodielectric response for practical applications.
207 citations
TL;DR: In this article, the transformation of a spatially spin-modulated magnetic structure in BiO3 into an ordinary spatially uniform structure of the LaFeO3 orthoferrite in Bi1−xLaxFeO 3 solid solutions is studied.
Abstract: By analyzing the NMR line shape, the transformation of a spatially spin-modulated magnetic structure in BiFeO3 into an ordinary spatially uniform structure of the LaFeO3 orthoferrite in Bi1−x
LaxFeO3 solid solutions is studied. The measurements are made using a spin-echo technique at temperatures of 77 and 4.2 K on ceramics with compositions x=0, 0.1, 0.2, 0.61, 0.9, and 1.0 enriched by the 57Fe isotope. It is shown that the spin-modulated structure disappears near the concentration x=0.2, which corresponds, according to the published data, to the phase transition with a change in the unit-cell symmetry R3c → C222. A formula is obtained describing the NMR absorption line shape for the spin-modulated structure with account of local line-width. Theoretical spectra adequately describe the evolution of the experimental spectrum in the concentration range 0≤x≤0.2. Highly nonuniform local magnetic fields in the intermediate compositions make it impossible to detect NMR signals in a sample with x=0.61. A uniform magnetic structure characterized by a single narrow line arises in the range of existence of a phase with the symmetry Pnma typical of the pure orthoferrite LaFeO3.
201 citations
TL;DR: In this paper, the authors showed that a small antiferromagnetic moment, parallel to [010] (y -direction), is induced in the field-induced phase (H ∥ z ).
Abstract: Neutron diffraction experiments on the heavy-fermion superconductor PrOs 4 Sb 12 revealed that a small antiferromagnetic moment, parallel to [010] ( y -direction), is induced in the field-induced phase ( H ∥ z ). The analysis, based on the Γ 1 singlet ground state crystal field model, shows that antiferro-order of O y z -type quadrupole moments of Pr ions is formed in the field-induced phase. This strongly suggests that the crystal field ground-state of Pr ions in PrOs 4 Sb 12 is the Γ 1 singlet and the quadrupolar ordering is induced due to level crossing with an excited state under a magnetic field.
199 citations
Book•
21 Apr 2003
TL;DR: A review of basic magnetostatics can be found in this paper, with a focus on magnetization and magnetic data storage, as well as magneto-optics and magnetooptic recording.
Abstract: 1. Review of basic magnetostatics 2. Magnetization and magnetic materials 3. Atomic origins of magnetism 4. Diamagnetism 5. Paramagnetism 6. Interactions in ferromagnetic materials 7. Ferromagnetic domains 8. Antiferromagnetism 9. Ferrimagnetism 10. Anisotropy 11. Magnetic data storage 12. Magneto-optics and magneto-optic recording 13. Magnetic semiconductors Solutions to problems.
185 citations
TL;DR: The magnetocaloric effect of Mn3GaC has been investigated in this article, which shows an antiferromagnetic to ferromagnetic transition at 165 K. In this compound, the magnetoric effect obtained at the transition is opposite to that of ordinary magnetoric systems.
Abstract: The magnetocaloric effect of Mn3GaC, which shows an antiferromagnetic to ferromagnetic transition at 165 K has been investigated. In this compound, magnetocaloric effect obtained at the transition is opposite to that of ordinary ferromagnetic systems, namely, negative magnetocaloric effect. It was found that a large magnetic entropy change, ΔSmag, of 15 J/kg K is obtained under an applied field of 2 T. The adiabatic temperature change, ΔTad, reaches 5.4 K in a field change of 2 T. At higher magnetic fields, both ΔSmag and ΔTad retain a large value over wide temperature range, exhibiting characteristic temperature dependence of a trapezoidal shape. These features are attributed to a sharp first-order transition retained in high magnetic fields as well as small magnetocrystalline anisotropy.
185 citations
TL;DR: In this article, an accurate ab initio full-potential augmented plane wave (FLAPW) electronic calculations within density functional theory in both local density and generalized gradient approximations have been performed for ordered alloys, focusing on their electronic and magnetic properties.
Abstract: Accurate ab initio full-potential augmented plane wave (FLAPW) electronic calculations within density functional theory in both local density and generalized gradient approximations have been performed for ${\mathrm{Mn}}_{x}{\mathrm{Ge}}_{1\ensuremath{-}x}$ and ${\mathrm{Mn}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}$ ordered alloys, focusing on their electronic and magnetic properties as a function of the host semiconducting matrix (ie, Si vs Ge), the Mn concentration, and the spin magnetic alignment (ie, ferromagnetic vs antiferromagnetic) As expected, Mn is found to be a source of holes and localized magnetic moments of about $3{\ensuremath{\mu}}_{B}/\mathrm{Mn}$ The results show that irrespective of the Mn content, the Ge-based systems are very close to half-metallicity, whereas the Si-based structures just miss the half-metallic behavior due to the crossing of the Fermi level by the lowest conduction bands Moreover, the ferromagnetic alignment is favored compared to the antiferromagnetic one, with its stabilization generally increasing with Mn content; this is in agreement with recent experimental findings for MnGe systems and supports the view that this class of ferromagnetic semiconductors constitute basic spintronic materials
183 citations
TL;DR: In this article, the growth, structural and magnetic characterization of (Ga,Mn)N epitaxial layers grown directly on 4H-SiC(0001) by reactive molecular-beam epitaxy is reported.
Abstract: We report on the growth, structural as well as magnetic characterization of (Ga,Mn)N epitaxial layers grown directly on 4H–SiC(0001) by reactive molecular-beam epitaxy. We focus on two layers grown under identical conditions except for the Mn/Ga flux ratio. Structural characterization reveals that the sample with the lower Mn content is a uniform alloy, while in the layer with the higher Mn content, Mn-rich clusters are found to be embedded in the (Ga,Mn)N alloy matrix. Although the magnetic behavior of both the samples is similar at low temperatures, showing antiferromagnetic characteristics with a spin-glass transition, the sample with higher Mn content additionally exhibits ferromagnetic properties at and above room temperature. This ferromagnetism most likely originates from the Mn-rich clusters in this sample.
178 citations
TL;DR: Using first-principles density functional calculations, it is shown that hexagonal metallic silicon nanotubes can be stabilized by doping with 3d transition metal atoms, interesting for silicon-based spintronic devices and other nanoscale magnetic applications.
Abstract: Using first-principles density functional calculations, we show that hexagonal metallic silicon nanotubes can be stabilized by doping with $3d$ transition metal atoms. Finite nanotubes doped with Fe and Mn have high local magnetic moments, whereas Co-doped nanotubes have low values and Ni-doped nanotubes are mostly nonmagnetic. The infinite ${\mathrm{S}\mathrm{i}}_{24}{\mathrm{F}\mathrm{e}}_{4}$ nanotube is found to be ferromagnetic with nearly the same local magnetic moment on each Fe atom as in bulk iron. Mn-doped nanotubes are antiferromagnetic, but a ferrromagnetic state lies only 0.03 eV higher in energy with a gap in the majority spin bands near the Fermi energy. These materials are interesting for silicon-based spintronic devices and other nanoscale magnetic applications.
TL;DR: It is reported that one-unit-cell-thick antiferromagnetic La2CuO4 barrier layers remain highly insulating and completely block a supercurrent; the characteristic decay length is 1 Å, indicating that the two phases do not mix.
Abstract: There is still no universally accepted theory of high-temperature superconductivity. Most models assume that doping creates ‘holes’ in the valence band of an insulating, antiferromagnetic ‘parent’ compound, and that antiferromagnetism and high-temperature superconductivity are intimately related1,2,3,4,5,6,7,8. If their respective energies are nearly equal, strong antiferromagnetic fluctuations (temporally and spatially restricted antiferromagnetic domains) would be expected in the superconductive phase, and superconducting fluctuations would be expected in the antiferromagnetic phase7; the two states should ‘mix’ over an extended length scale8. Here we report that one-unit-cell-thick antiferromagnetic La2CuO4 barrier layers remain highly insulating and completely block a supercurrent; the characteristic decay length is 1 A, indicating that the two phases do not mix. We likewise found that isolated one-unit-cell-thick layers of La1.85Sr0.15CuO4 remain superconducting. The latter further implies that, on doping, new electronic states are created near the middle of the bandgap. These two findings are in conflict with most proposed models, with a few notable exceptions that include postulated spin–charge separation2.
TL;DR: The magnetic reversal and domain structure in antiferromagnetically coupled Co/Pt multilayers that are isomorphic to layeredAntiferromagnetic films with perpendicular magnetic anisotropy are reported on.
Abstract: Magnetic multilayer films provide convenient model systems for studying the physics of antiferromagnetic films and surfaces. Here we report on the magnetic reversal and domain structure in antiferromagnetically coupled Co/Pt multilayers that are isomorphic to layered antiferromagnetic films with perpendicular magnetic anisotropy. We observe two distinct remanent states and reversal modes of the system. In mode 1 the magnetization in each layer reverses independently, producing an antiferromagnetic remanent state that shows full lateral correlation and vertical anticorrelation across the interlayers. In mode 2 the reversal in adjacent layers is locally synchronized with a remanent state that is vertically correlated but laterally anticorrelated in ferromagnetic stripe domains. Theoretical energy calculations of the two ground states identify a new phase boundary that is in good agreement with our experimental results.
TL;DR: Hobbs et al. as discussed by the authors investigated the spin-density-functional properties of the complex structural and magnetic phase behaviors of Mn and found that the antiferromagnetic Mn I-Mn II coupling is strongest, leading to stabilization of a ferrimagnetic phase upon slight expansion.
Abstract: In the preceding paper [D. Hobbs, J. Hafner, and D. Spi\ifmmode \check{s}\else \v{s}\fi{}\'ak, Phys. Rev. B 68, 014407 (2003)], we have started an ab initio spin-density-functional study of the complex structural and magnetic phase behaviors of Mn by a detailed investigation of \ensuremath{\alpha}-Mn. It was shown that the complex crystalline and noncollinear antiferromagnetic structures are the results of the conflicting tendencies to maximize simultaneously bond strength and magnetic moment. The present work extends this study to the remaining four polymorphs of Mn. Frustration of antiferromagnetic exchange interaction (which is the driving force leading to noncollinearity in \ensuremath{\alpha}-Mn) is found to be even stronger in \ensuremath{\beta}-Mn. However, in contrast to the current assumption that the magnetic frustration is restricted to the sublattice of the Mn II atoms, with the Mn I atoms remaining nonmagnetic, we find that the antiferromagnetic Mn I-Mn II coupling is strongest, leading to the stabilization of a ferrimagnetic phase upon slight expansion. At equilibrium, a nonmagnetic and a weakly ferrimagnetic phase are energetically virtually degenerate. Antiferromagnetic ground states are found for \ensuremath{\gamma}- and \ensuremath{\delta}-Mn (face- and body-centered cubic, respectively), while hexagonal \ensuremath{\epsilon}-Mn is only marginally magnetic at equilibrium. Magnetism strongly influences the mechanical properties of all polymorphs. Due to the stabilization of the antiferromagnetic state on expansion, the \ensuremath{\gamma}- and \ensuremath{\delta}-phase are exceptionally soft, whereas \ensuremath{\beta}- and \ensuremath{\epsilon}-Mn where magnetism is nearly completely suppressed are mechanically hard. \ensuremath{\alpha}-Mn is found to be soft in the noncollinear antiferromagnetic state, but hard in the nonmagnetic phase. \ensuremath{\alpha}-Mn is found to have the lowest energy at ambient pressure, under compression a structural phase transition to \ensuremath{\epsilon}-Mn is predicted, in agreement with recent experiments. In summary, the structural and magnetic phase diagram of even the complex metallic element is well explained by the density-functional theory.
TL;DR: In this article, the electronic structure and magnetic properties of binary compounds consisting of $3d$ transition metals and group V elements, viz., P, Sb, and As in the zinc-blende structure, were investigated.
Abstract: New materials are currently sought for use in spintronics applications. Ferromagnetic materials with half metallic properties are valuable in this respect. Here we present the electronic structure and magnetic properties of binary compounds consisting of $3d$ transition metals and group V elements, viz., P, Sb, and As in the zinc-blende structure. We demonstrate that compounds of V, Cr, and Mn show half metallic behavior for appropriate lattice constants. By comparing the total energies in the ferromagnetic and antiferromagnetic structures, we have ascertained that the ferromagnetic phase is stable over the antiferromagnetic one. Of the different compounds studied, the Cr based systems exhibit the strongest interatomic exchange interactions, and are hence predicted to have the highest critical temperatures. Also, we predict that VAs under certain growth conditions should be a semiconducting ferromagnet. Moreover, critical temperatures of selected half metallic compounds have been estimated from mean field theory and Monte Carlo simulations using parameters obtained from a ab initio noncollinear, tight binding linearized muffin-tin orbital method. From a simple model, we calculate the reflectance from an ideal MnAs/InAs interface considering the band structures of MnAs and InAs. Finally, we present results on the relative stabilities of MnAs and CrSb compounds in the NiAs and zinc-blende structures, and suggest a parameter space in substrate lattice spacings for when the zinc-blende structure is expected to be stable.
TL;DR: It was found that the intermolecular interactions have a significant effect on the manifestation of slow relaxation of the magnetization, and thereby, these complexes represent a new family of "exchange-biased single-molecule magnets", where the exchange bias is controlled by chemical and structural modifications.
Abstract: A new family of tetranuclear Mn complexes [Mn4X4L4] (H2L = salicylidene-2-ethanolamine; X = Cl (1) or Br (2)) and [Mn4Cl4(L‘)4] (H2L‘ = 4-tert-butyl-salicylidene-2-ethanolamine, (3)) has been synthesized and studied. Complexes 1−3 possess a square-shaped core with ferromagnetic exchange interactions between the four MnIII centers resulting in an S = 8 spin ground state. Magnetochemical studies and high-frequency EPR spectroscopy reveal an axial magnetoanisotropy with D values in the range −0.10 to −0.20 cm-1 for complexes 2 and 3 and for differently solvated forms of 1. As a result, these species possess an anisotropy-induced energy barrier to magnetization reversal and display slow relaxation of the magnetization, which is observed as hysteresis for 1 and 3 and frequency-dependent peaks in out-of-phase AC susceptibility measurements for 3. The effective energy barrier was determined to be 7.7 and 7.9 K for 1 and 3, respectively, and evidence for quantum tunneling of the magnetization was observed. Detail...
TL;DR: In this paper, the properties of the perovskites NdBaCo 2 O 5+ δ have been studied as a function of temperature by neutron powder diffraction and long-range G-type antiferromagnetic order is realized for all samples apart from that with δ = 0.5.
TL;DR: The antiferromagnetic interlayer exchange coupling for the 11 A NiO layer shows an increase in coupling strength with increasing temperature, in agreement with the quantum interference model of Bruno for insulating spacer layers.
Abstract: Interlayer exchange coupling that oscillates between antiferromagnetic and ferromagnetic as a function of NiO thickness has been observed in [Pt(5 A)/Co(4 A)](3)/NiO(t(NiO) A)/[Co(4 A)/Pt(5 A)](3) multilayers with out-of-plane anisotropy. The period of oscillation corresponds to approximately 2 monolayers of NiO. This oscillatory behavior is possibly attributed to the antiferromagnetic ordering in NiO. The antiferromagnetic interlayer exchange coupling for the 11 A NiO layer shows an increase in coupling strength with increasing temperature, in agreement with the quantum interference model of Bruno for insulating spacer layers. A coexistence of exchange biasing and antiferromagnetic interlayer exchange coupling has been observed below T=250 K.
TL;DR: In this article, an ultrathin nonmagnetic Pt spacer is placed between the multilayer (ML) and the antiferromagnetic (AFM) layer to enhance the magnitude of exchange bias.
Abstract: In (Pt/Co)n/FeMn multilayers, the magnitude of exchange bias, HE, can be considerably enhanced by placing an ultrathin nonmagnetic Pt spacer between the multilayer (ML) and the antiferromagnetic (AFM) layer. The bias is maximum for a spacer layer thickness, t, of a few angstroms and it decreases progressively as t is further increased. This bias enhancement is accompanied by an increase of coercivity, HC. This behavior is due to the role of the Pt spacer in enhancing the perpendicular effective anisotropy of the last Co layer in the ML, which has the effect of increasing the net ferromagnetic (FM)/AFM spin projection, thus leading to the HE and HC enhancements. The decrease of HE and HC for thicker spacer layers is due to the limited range of the FM–AFM proximity effect.
TL;DR: In this article, the ordering process of a two-dimensional Ising triangular antiferromagnet is described, and the possibility of one-dimensional features at high T is discussed.
Abstract: Specific heat and magnetization measurements have been carried out under a range of magnetic fields on single crystals of ${\mathrm{Ca}}_{3}{\mathrm{Co}}_{2}{\mathrm{O}}_{6}.$ This compound is composed of Ising magnetic chains that are arranged on a triangular lattice. The intrachain and interchain couplings are ferromagnetic and antiferromagnetic, respectively. This situation gives rise to geometrical frustration, that bears some similarity to the classical problem of a two-dimensional Ising triangular antiferromagnet. This paper reports on the ordering process at low T and the possibility of one-dimensional features at high T.
TL;DR: Numerical investigation of the domain state model evidence is gained that this effect depends on the angle between the easy axis of the antiferromagnet and the applied magnetic field.
Abstract: Experimentally an asymmetry of the reversal modes has been found in certain exchange bias systems. From a numerical investigation of the domain state model evidence is gained that this effect depends on the angle between the easy axis of the antiferromagnet and the applied magnetic field. Depending on this angle the ferromagnet reverses either symmetrically, e.g., by a coherent rotation on both sides of the loop, or the reversal is asymmetric with a nonuniform reversal mode for the ascending branch, which may even yield a zero perpendicular magnetization.
TL;DR: Quantitative analysis of the MFM images revealed that 7% of the spins at the interface are uncompensated and contribute to the exchange biasing.
Abstract: Magnetic force microscopy (MFM) measurements were performed on an exchange-biased $\mathrm{C}\mathrm{o}\mathrm{O}/\phantom{\rule{0ex}{0ex}}(\mathrm{C}\mathrm{o}\mathrm{P}\mathrm{t})$ multilayer sample at 7.5 K. Applying an external magnetic field of up to 7 T saturates the ferromagnetic layer and the remaining uncompensated antiferromagnetic spins at the antiferromagnet-ferromagnet interfaces are imaged with high lateral resolution. The coupling between the uncompensated spins and the spins in the ferromagnet are found to be antiferromagnetic. Quantitative analysis of the MFM images revealed that 7% of the spins at the interface are uncompensated and contribute to the exchange biasing.
TL;DR: In this paper, it was found that the tunneling of spin-polarized electrons across the antiferromagnetic coupled grain boundaries dominates the transport properties of polycrystalline Fe3O4 films.
Abstract: Polycrystalline Fe3O4 films have been prepared by reactive sputtering at room temperature. Transmission electron microscopy images show that the films consist of quite uniform Fe3O4 grains well separated by grain boundaries. It was found that the tunneling of spin-polarized electrons across the antiferromagnetic coupled grain boundaries dominates the transport properties of the films. Magnetoresistance (MR) {=[ρ(H)−ρ(0)]/ρ(0)} shows linear and quadratic magnetic-field dependence in the low-field range when the field is applied parallel and perpendicular to film plane, which is similar to the behaviors observed in the epitaxial Fe3O4 films consisting of a large fraction of antiferromagnetic antiphase domain boundaries. At 300 K, the size of the MR reaches −7.4% under a 50-kOe magnetic field, which is a very large MR for polycrystalline Fe3O4 films.
TL;DR: In this article, a possibility of the realization of the p-wave spin-singlet superconductivity (p SS), whose gap function is odd both in momentum and in frequency, is investigated by solving the gap equation with the phenomenological interaction mediated by the antiferromagnetic spin fluctuation.
Abstract: A possibility of the realization of the p -wave spin–singlet superconductivity ( p SS), whose gap function is odd both in momentum and in frequency, is investigated by solving the gap equation with the phenomenological interaction mediated by the antiferromagnetic spin fluctuation. The p SS is realized prevailing over the d -wave singlet superconductivity ( d SS) in the vicinity of antiferromagnetic quantum critical point (QCP) both on the paramagnetic and on the antiferromagnetic sides. Off the QCP in the paramagnetic phase, however, the d SS with line-nodes is realized as conventional anisotropic superconductivity. For the present p SS state, there is no gap in the quasiparticle spectrum everywhere on the Fermi surface due to its odd frequency. These features can give a qualitative understanding of the anomalous behaviors of NQR relaxation rate on CeCu 2 Si 2 or CeRhIn 5 where the antiferromagnetism and superconductivity coexist on a microscopic level.
TL;DR: In this paper, the doping dependence of the electronic structure and magnetic properties in hexagonal hexagonal materials was investigated, and a weak itinerant ferromagnetic state was predicted for all doping levels in range $x = 0.3$ to $x=0.7$ with competing but weaker itinerant antiferromagnetic solutions.
Abstract: Density-functional calculations are used to investigate the doping dependence of the electronic structure and magnetic properties in hexagonal ${\mathrm{Na}}_{x}{\mathrm{CoO}}_{2}.$ The electronic structure is highly two dimensional, even without accounting for the structural changes associated with hydration. At the local spin-density approximation level, a weak itinerant ferromagnetic state is predicted for all doping levels in range $x=0.3$ to $x=0.7,$ with competing but weaker itinerant antiferromagnetic solutions. Comparison with experiment implies substantial magnetic quantum fluctuations. Based on the simple Fermi surface and the ferromagnetic tendency of this material, it is speculated that a triplet superconducting state analogous to that in ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ may exist here.
TL;DR: Two new transition-metal tellurium oxy-chlorides of the general formula Ni 5 (TeO 3 ) 4 X 2 (X = Cl, Br) have been isolated during the investigation of the ternary phase diagram NiO-NiCl 2 -TeO 2.
Abstract: Two new transition-metal tellurium oxy-chlorides of the general formula Ni 5 (TeO 3 ) 4 X 2 (X = Cl, Br) have been isolated during the investigation of the ternary phase diagram NiO-NiCl 2 -TeO 2 . They crystallize in the monoclinic system, space group C2/c, and for the case of Ni 5 (TeO 3 ) 4 Cl 2 the unit cell is a = 19.5674(2) , b = 5.2457(1) A, and c = 16.3084(1) A, with β = 125.289(1)°. The structure is layered and built up of corner-connected [Ni 5 O 17 X 2 ] entities, made of five nickel(II) octahedra associated by edge and face sharing. The tellurium-(IV) atoms are fixed upon the nickel layers. Their lone pairs E and the halogen atoms are packed in a double layer perpendicular to the [010] direction. From the magnetic point of view, this system provides a new 2D S = 1 quantum spin system with antiferromagnetic superexchange interaction. The magnetic susceptibility shows anomalies pointing to magnetic ordering phenomena. The observed transition temperatures vary with the interlayer separation.
TL;DR: The structure of antiferromagnetic (AFM) domain walls and their interaction with lattice strain are derived taking the multiple-order-parameter compound YMnO3 as a model example and leads to a piezomagnetic clamping of the electric and magnetic order parameters in good agreement with the available experimental data.
Abstract: The structure of antiferromagnetic (AFM) domain walls and their interaction with lattice strain are derived taking the multiple-order-parameter compound YMnO3 as a model example. Contrary to the conviction that AFM domain walls are energetically unfavorable, their interaction with lattice strain lowers the total energy of the system and leads to a piezomagnetic clamping of the electric and magnetic order parameters in good agreement with the available experimental data.
TL;DR: X-ray diffraction analysis reveals that these complexes are isostructural and have a novel chain structure and a spin frustration phenomenon was found in complex 4, which results from the ferro-ferro-antiferromagnetic exchanges in the trigonal Cu-Gd-Cr units.
Abstract: A series of cyano-bridged heterotrimetallic complexes [CuL](2)Ln(H(2)O)(2)M(CN)(6).7H(2)O have been synthesized by the reactions of CuL (L(2)(-) = dianion of 1,4,8,11-tetraazacyclotradecane-2,3-dione), Ln(3+) (Ln = Gd or La), and [M(CN)(6)](3)(-) (M = Co, Fe, or Cr). X-ray diffraction analysis reveals that these complexes are isostructural and have a novel chain structure. The Ln(3+) ion is eight-coordinated by six oxygen atoms of two CuL and two water molecules and two nitrogen atoms of the bridging cyano ligands of two [M(CN)(6)](3)(-), while the [M(CN)(6)](3)(-) anion connects two Ln(3+) using two trans-CN(-) ligands giving rise to a chainlike structure. In the chain, every CuL group tilts toward the CN(-) ligand of adjacent [M(CN)(6)](3)(-) with the Cu-N(cyano) contacts ranging from 2.864(6) to 2.930(6) A. Magnetic studies on the CuGdCo complex (1) indicate the presence of ferromagnetic coupling between Cu(II) and Gd(III). The CuLaCr (5) and CuLaFe (2) complexes exhibit ferromagnetic interaction between paramagnetic Cu(II) and Cr(III)/Fe(III) ions through the weak cyano bridges (Cu-N(cyano) = 2.930(6) A for 2). A global ferromagnetic interaction is operative in the CuGdFe complex (3) with the concurrence of dominant ferromagnetic Cu(II)-Gd(III) and minor antiferromagnetic Gd(III)-Fe(III) as well as the ferromagnetic Cu(II)-Fe(III) interaction. For the CuGdCr complex (4), an overall antiferromagnetic behavior was observed, which is attributed to the presence of dominant antiferromagnetic Cr(III)-Gd(III) coupling and the minor ferromagnetic Cu(II)-Gd(III) and Cu(II)-Cr(III) interaction. Moreover, a spin frustration phenomenon was found in complex 4, which results from the ferro-ferro-antiferromagnetic exchanges in the trigonal Cu-Gd-Cr units. The magnetic susceptibilities of these complexes were simulated using suitable models. The magneto-structural correlation was investigated. These complexes did not show a magnetic phase transition down to 1.8 K.
TL;DR: In this article, a first-principles band structure calculation is carried out for new room-temperature ferromagnets, zinc blende CrSb and CrAs.
Abstract: Theoretical study based on a first-principles band structure calculation is carried out for new room-temperature ferromagnets, zinc blende CrSb and CrAs. It is found from the total-energy calculation that the ferromagnetic state is energetically favorable for both materials. By using the value of the difference in total energy between ferromagnetic and the antiferromagnetic states, the Curie temperatures of these ferromagnets are estimated as 1600–1800 K within mean-field approximation of the Heisenberg model. The magnetic moment is evaluated to be 3 Bohr magnetons per formula unit for both materials, which agrees well with the saturation moments estimated experimentally. Furthermore, these ferromagnets are half metallic, and the spin polarization at the Fermi level is almost unaffected even if spin–orbit interaction is taken into account.
TL;DR: Systematic measurements of ac susceptibility, nuclear-quadrupole-resonance spectrum, and nuclear-spin-lattice-relaxation time (T1) on the pressure-induced heavy-fermion superconductor CeRhIn5 show that antiferromagnetism (AFM) and superconductivity (SC) coexist microscopically, and point to the unconventional characteristics of SC coexisting with AFM.
Abstract: We report systematic measurements of ac susceptibility, nuclear-quadrupole-resonance spectrum, and nuclear-spin-lattice-relaxation time (T1) on the pressure (P)-induced heavy-fermion superconductor CeRhIn5. The temperature (T) dependence of 1/T(1) at P=1.6 GPa has revealed that antiferromagnetism (AFM) and superconductivity (SC) coexist microscopically, exhibiting the respective transition at T(N)=2.8 K and T(MF)(c)=0.9 K. It is demonstrated that SC does not yield any trace of gap opening in low-lying excitations below T(onset)(c)=2 K, but T(MF)(c)=0.9 K, followed by a T(1)T=const law. These results point to the unconventional characteristics of SC coexisting with AFM. We highlight that both of the results deserve theoretical work on the gapless nature in the low-lying excitation spectrum due to the coexistence of AFM and SC and the lack of the mean-field regime below T(onset)(c)=2 K.