Showing papers on "Magnetic structure published in 2012"
TL;DR: It is demonstrated how interfacial interactions can induce a complex magnetic structure in a non-magnetic material and specifically show that exchange bias can unexpectedly emerge in heterostructures consisting of paramagnetic LaNiO3 (LNO) and ferromagnetic LaMnO 3 (LMO).
Abstract: Interfaces between insulating oxides have revealed exotic electronic and magnetic properties. It is now shown that a complex magnetic structure can emerge in an oxide superlattice, and that specific interfaces can unexpectedly exhibit exchange bias. The observations reveal the induction of antiferromagnetism in a material that is usually paramagnetic.
379 citations
TL;DR: The skyrmion phase was stable over a wide range of temperatures and magnetic fields in the thin samples, and the lattice constant was estimated to be 18 nm, almost identical to the helical period.
Abstract: Observing and characterizing the spin distributions on a nanometer scale are of vital importance for understanding nanomagnetism and its application to spintronics. The magnetic structure in MnSi thin samples prepared from a bulk, which undergoes a transition from a helix to a skyrmion lattice, was investigated by in situ observation using Lorentz microscopy. Stripe domains were observed at zero applied field below 22.5 K. A skyrmion lattice with 6-fold symmetry in real space appeared when a field of 0.18 T was applied normal to the film plane. The lattice constant was estimated to be 18 nm, almost identical to the helical period. In comparison with the marginally stable skyrmion phase in a bulk sample, the skyrmion phase was stable over a wide range of temperatures and magnetic fields in the thin samples.
281 citations
TL;DR: In this article, the magnetic structure and magnetization dynamics of systems of plane frustrated Ising chain lattices are reviewed for three groups of compounds:,,, and. The available experimental data are analyzed and compared in detail.
Abstract: The magnetic structure and magnetization dynamics of systems of plane frustrated Ising chain lattices are reviewed for three groups of compounds: , , and . The available experimental data are analyzed and compared in detail. It is shown that a high-temperature magnetic phase on a triangle lattice is normally and universally a partially disordered antiferromagnetic (PDA) structure. The diversity of low-temperature phases results from weak interactions that lift the degeneracy of a 2D antiferromagnetic Ising model on the triangle lattice. Mean-field models, Monte Carlo simulation results on the static magnetization curve, and results on slow magnetization dynamics obtained with Glauber's theory are discussed in detail.
193 citations
TL;DR: Kapellasite, Cu3Zn(OH)6Cl2, a geometrically frustrated spin-1/2 kagome antiferromagnet polymorphic with herbertsmithite, is a gapless spin liquid showing unusual dynamic short-range correlations of noncoplanar cuboc2 type which persist down to 20 mK.
Abstract: Magnetic susceptibility, NMR, muon spin relaxation, and inelastic neutron scattering measurements show that kapellasite, Cu3Zn(OH)6Cl2, a geometrically frustrated spin-1/2 kagome antiferromagnet polymorphic with herbertsmithite, is a gapless spin liquid showing unusual dynamic short-range correlations of noncoplanar cuboc2 type which persist down to 20 mK. The Hamiltonian is determined from a fit of a high-temperature series expansion to bulk susceptibility data and possesses competing exchange interactions. The magnetic specific heat calculated from these exchange couplings is in good agreement with experiment. The temperature dependence of the magnetic structure factor and the muon relaxation rate are calculated in a Schwinger-boson approach and compared to experimental results.
176 citations
TL;DR: In this article, the density functional theory DFT+U calculations are used to investigate α-MnO2, a structure containing a framework of corner and edge sharing MnO6 octahedra with tunnels in between.
133 citations
TL;DR: A combination of powder and single crystal neutron diffraction measurements below the magnetic order transition has been used to determine unequivocally the magnetic structure of this Néel N-Type ferrimagnet, proving that the ferrimagnetic behavior is due to a noncompensation of the different Fe(II) and Fe(III) magnetic moments.
Abstract: Neutron diffraction studies have been carried out to shed light on the unprecedented order-disorder phase transition (ca. 155 K) observed in the mixed-valence iron(II)-iron(III) formate framework compound [NH2(CH3)2]n[FeIIIFeII(HCOO)6]n. The crystal structure at 220 K was first determined from Laue diffraction data, then a second refinement at 175 K and the crystal structure determination in the low temperature phase at 45 K were done with data from the monochromatic high resolution single crystal diffractometer D19. The 45 K nuclear structure reveals that the phase transition is associated with the order-disorder of the dimethylammonium counterion that is weakly anchored in the cavities of the [FeIIIFeII(HCOO)6]n framework. In the low-temperature phase, a change in space group from P31c to R3c occurs, involving a tripling of the c-axis due to the ordering of the dimethylammonium counterion. The occurrence of this nuclear phase transition is associated with an electric transition, from paraelectric to antiferroelectric. A combination of powder and single crystal neutron diffraction measurements below the magnetic order transition (ca. 37 K) has been used to determine unequivocally the magnetic structure of this Neel N-Type ferrimagnet, proving that the ferrimagnetic behavior is due to a noncompensation of the different FeII and FeIII magnetic moments.
127 citations
TL;DR: In this article, the authors investigated the magnetic structure in a polycrystalline sample of the B20-type MnGe by means of small-angle neutron scattering and found that a Debye-ring-like pattern appeared due to the random orientation of the spin helix q vectors (∥ ).
Abstract: We have investigated the magnetic structure in a polycrystalline sample of the B20-type MnGe by means of small-angle neutron scattering. On the projected diffraction plane normal to the incoming neutron beam, a Debye-ring-like pattern appears due to the random orientation of the spin helix q vectors (∥ ). When an external magnetic field is applied normal to the incoming neutron beam, an intense peak with wave vector (q) perpendicular to the applied magnetic field is observed as the hallmark of the formation of a skyrmion lattice with a multiple-q helix in a wide temperature-magnetic-field region. This scattering intensity remains even after removing the magnetic field, which indicates that a skyrmion lattice is stabilized as the ground state. A different form of skyrmion lattice, either square or cubic, is proposed, which is also shown to be in good agreement with previous high-angle neutron diffraction results. Calculations based on such structures also describe the magnetic-field profile of the topological Hall resistivity.
115 citations
TL;DR: In this article, powder neutron diffraction and inelastic scattering measurements of frustrated pyrochlore Nd 2 Ir 2 O 7, which exhibits a metal-insulator transition at a temperature T MI of 33 K.
Abstract: In this study, we performed powder neutron diffraction and inelastic scattering measurements of frustrated pyrochlore Nd 2 Ir 2 O 7 , which exhibits a metal–insulator transition at a temperature T MI of 33 K. The diffraction measurements revealed that the pyrochlore has an antiferromagnetic long-range structure with propagation vector q 0 of (0,0,0) and that it grows with decreasing temperature below 15 K. This structure was analyzed to be of the all-in all-out type, consisting of highly anisotropic Nd 3+ magnetic moments of magnitude 2.3±0.4µ B , where µ B is the Bohr magneton. The inelastic scattering measurements revealed that the Kramers ground doublet of Nd 3+ splits below T MI . This suggests the appearance of a static internal magnetic field at the Nd sites, which probably originates from a magnetic order consisting of Ir 4+ magnetic moments. Here, we discuss a magnetic structure model for the Ir order and the relation of the order to the metal–insulator transition in terms of frustration.
105 citations
TL;DR: It is suggested that the peculiar metal-insulator transition is not caused by the Slater mechanism as believed earlier but by an alternative mechanism related to the formation of the specific tetrahedral magnetic order on the pyrochlore lattice in the presence of strong spin-orbit interactions.
Abstract: ${\mathrm{Cd}}_{2}{\mathrm{Os}}_{2}{\mathrm{O}}_{7}$ shows a peculiar metal-insulator transition at 227 K with magnetic ordering in a frustrated pyrochlore lattice, but its magnetic structure in the ordered state and the transition origin are yet uncovered. We observed a commensurate magnetic peak by resonant x-ray scattering in a high-quality single crystal. X-ray diffraction and Raman scattering experiments confirmed that the transition is not accompanied with any spatial symmetry breaking. We propose a noncollinear all-in--all-out spin arrangement on the tetrahedral network made of Os atoms. Based on this we suggest that the transition is not caused by the Slater mechanism as believed earlier but by an alternative mechanism related to the formation of the specific tetrahedral magnetic order on the pyrochlore lattice in the presence of strong spin-orbit interactions.
101 citations
TL;DR: This work demonstrates spin-valve-like magnetoresistance at room temperature in a bulk ferrimagnetic material that exhibits a magnetic shape memory effect in Mn(2)NiGa bulk lattice.
Abstract: Spin valves have revolutionized the field of magnetic recording and memory devices. Spin valves are generally realized in thin film heterostructures, where two ferromagnetic (FM) layers are separated by a nonmagnetic conducting layer. Here, we demonstrate spin-valve-like magnetoresistance at room temperature in a bulk ferrimagnetic material that exhibits a magnetic shape memory effect. The origin of this unexpected behavior in Mn2NiGa has been investigated by neutron diffraction, magnetization, and ab initio theoretical calculations. The refinement of the neutron diffraction pattern shows the presence of antisite disorder where about 13% of the Ga sites are occupied by Mn atoms. On the basis of the magnetic structure obtained from neutron diffraction and theoretical calculations, we establish that these antisite defects cause the formation of FM nanoclusters with parallel alignment of Mn spin moments in a Mn2NiGa bulk lattice that has antiparallel Mn spin moments. The direction of the Mn moments in the soft FM cluster reverses with the external magnetic field. This causes a rotation or tilt in the antiparallel Mn moments at the cluster-lattice interface resulting in the observed asymmetry in magnetoresistance.
75 citations
TL;DR: In this paper, the instantaneous free magnetic energy and relative magnetic helicity of an unknown three-dimensional nonlinear force-free (NLFF) magnetic structure extending above a single known lower-boundary magnetic field vector are derived.
Abstract: Expanding on an earlier work that relied on linear force-free (LFF) magnetic fields, we self-consistently derive the instantaneous free magnetic energy and relative magnetic helicity budgets of an unknown three-dimensional nonlinear force-free (NLFF) magnetic structure extending above a single known lower-boundary magnetic field vector. The proposed method does not rely on the detailed knowledge of the three-dimensional field configuration but is general enough to employ only a magnetic connectivity matrix on the lower boundary. The calculation yields a minimum free magnetic energy and a relative magnetic helicity consistent with this free magnetic energy. The method is directly applicable to photospheric or chromospheric vector magnetograms of solar active regions. Upon validation, it basically reproduces magnetic energies and helicities obtained by well known, but computationally more intensive and non-unique, methods relying on the extrapolated three-dimensional magnetic field vector. We apply the method to three active regions, calculating the photospheric connectivity matrices by means of simulated annealing, rather than a model-dependent NLFF extrapolation. For two of these regions we correct for the inherent LFF overestimation in free energy and relative helicity that is larger for larger, more eruptive, active regions. In the third region studied, our calculation can lead to a physical interpretation of observed eruptive manifestations. We conclude that the proposed method, including the proposed inference of the magnetic connectivity matrix, is practical enough to contribute to a physical interpretation of the dynamical evolution of solar active regions.
TL;DR: In this paper, the magnetization distributions in individual soft magnetic permalloy caps on non-magnetic spherical particles with sizes ranging from 50 to 800 nm were investigated and the phase diagram of equilibrium magnetic states was calculated theoretically.
Abstract: The magnetization distributions in individual soft magnetic permalloy caps on non-magnetic spherical particles with sizes ranging from 50 to 800 nm are investigated. We experimentally visualize the magnetic structures at the resolution limit of the x-ray magnetic circular dichroism photoelectron emission microscopy (XMCD-PEEM). By analyzing the so-called tail contrast in XMCD-PEEM, the spatial resolution is significantly enhanced, which allowed us to explore magnetic vortices and their displacement on curved surfaces. Furthermore, cap nanostructures are modeled as extruded hemispheres to determine theoretically the phase diagram of equilibrium magnetic states. The calculated phase diagram agrees well with the experimental observations.
TL;DR: An unprecedented magneto-orbital texture in multiferroic CaMn(7)O(12), found to give rise to the largest magnetically induced ferroelectric polarization measured to date, opens up the possibility of discovering newMultiferroics with even larger polarization and higher transition temperatures.
Abstract: Orbital physics drives a rich phenomenology in transition-metal oxides, providing the microscopic underpinning for effects such as Colossal Magnetoresistance. In particular, magnetic and lattice degrees of freedom are coupled through orbital ordering, and it has long been hoped that this coupling could be exploited to create high-temperature multiferroics with large values of the electrical polarization. Here we report an unprecedented magneto-orbital texture in multiferroic CaMn7O12, found to give rise to the largest magnetically induced ferroelectric polarization measured to date. X-ray diffraction characterization of the structural modulation in these ‘magneto-orbital helices’, and analysis of magnetic exchange shows that orbital order is crucial in stabilising a chiral magnetic structure, thus allowing for electric polarization. Additionally, the presence of a global structural rotation enables the coupling between this polarization and magnetic helicity required for multiferroicity. These novel principles open up the possibility of discovering new multiferroics with even larger polarization and higher transition temperatures. The coupling of magnetism and ferroelectricity is of relevance for applications such as sensing, but occurs only rarely in bulk materials. The large magnetically induced ferroelectric polarization observed here in CaMn7O12establishes a new approach to achieve a strong magnetoelectric coupling.
TL;DR: MAGNEXT as discussed by the authors is a computer program available from the Bilbao Crystallographic Server that provides symmetry-forced systematic absences or extinction rules of magnetic nonpolarized neutron diffraction.
Abstract: MAGNEXT is a new computer program available from the Bilbao Crystallographic Server (http://www.cryst.ehu.es) that provides symmetry-forced systematic absences or extinction rules of magnetic nonpolarized neutron diffraction. For any chosen Shubnikov magnetic space group, the program lists all systematic absences, and it can also be used to obtain the list of the magnetic space groups compatible with a particular set of observed systematic absences. Absences corresponding to specific ordering modes can be derived by introducing effective symmetry operations associated with them. Although systematic extinctions in neutron diffraction do not possess the strong symmetry-resolving power of those in nonmagnetic crystallography, they can be important for the determination of some magnetic structures. In addition, MAGNEXT provides the symmetry-adapted form of the magnetic structure factor for different types of diffraction vectors, which can then be used to predict additional extinctions caused by some prevailing orientation of the atomic magnetic moments. This program, together with a database containing comprehensive general information on the symmetry operations and the Wyckoff positions of the 1651 magnetic space groups, is the starting point of a new section in the Bilbao Crystallographic Server devoted to magnetic symmetry and its applications.
TL;DR: Results demonstrate that the ground state is composed of coexisting E-type and cycloidal states, and clarify the origin of the large polarization to be caused by the E- type antiferromagnetic states in the orthorhombic YMnO(3) thin film.
Abstract: We investigated the magnetic structure of an orthorhombic YMnO(3) thin film by resonant soft x-ray and hard x-ray diffraction. We observed a temperature-dependent incommensurate magnetic reflection below 45 K and a commensurate lattice-distortion reflection below 35 K. These results demonstrate that the ground state is composed of coexisting E-type and cycloidal states. Their different ordering temperatures clarify the origin of the large polarization to be caused by the E-type antiferromagnetic states in the orthorhombic YMnO(3) thin film.
TL;DR: In this article, the magnetic properties and electronic structures of NdFeO3 have been studied by performing accurate first principle calculation based on density functional theory, where the 4f-electrons of the compound were explicitly treated as valence electrons.
Abstract: Magnetic properties and electronic structures of NdFeO3 have been studied by performing accurate first principle calculation based on density functional theory The 4f-electrons of Nd are explicitly treated as valence electrons The simulation results of crystal structure and magnetic structure of this compound agree well with the experimental observations Importantly, our study indicates that the spin reorientation transition of Fe3+ spin sublattice can be ascribed to the exchange interaction between Nd-4f and Fe-3d electrons, which are mediated by O2-2p state in Fe-O plane As the temperature decreases, the Fe-O and Nd-O bonds become more covalent, and the exchange interactions become stronger
TL;DR: The results show that the unusual appearance and disappearance of the C2 phase is accompanied by magnetic ordering, which implies that phase separation occurs in Mn(3)ZnN.
Abstract: The antiperovskite Mn(3)ZnN is studied by neutron diffraction at temperatures between 50 and 295 K. Mn(3)ZnN crystallizes to form a cubic structure at room temperature (C1 phase). Upon cooling, another cubic structure (C2 phase) appears at around 177 K. Interestingly, the C2 phase disappears below 140 K. The maximum mass concentration of the C2 phase is approximately 85% (at 160 K). The coexistence of C1 and C2 phase in the temperature interval of 140-177 K implies that phase separation occurs. Although the C1 and C2 phases share their composition and lattice symmetry, the C2 phase has a slightly larger lattice parameter (Δa ≈ 0.53%) and a different magnetic structure. The C2 phase is further investigated by neutron diffraction under high-pressure conditions (up to 270 MPa). The results show that the unusual appearance and disappearance of the C2 phase is accompanied by magnetic ordering. Mn(3)ZnN is thus a valuable subject for study of the magneto-lattice effect and phase separation behavior because this is rarely observed in nonoxide materials.
TL;DR: In this paper, an experimental and theoretical study of CuMn-V compounds was carried out, and the results were based on X-ray diffraction, magnetization, transport and differential thermal analysis measurements, and on density-functional theory calculations of the magnetic structure of the compounds.
TL;DR: The studies suggest that investigation of MCE is an effective technique to acquire fundamental understanding about the basic magnetic structure of a system with complex competing interactions.
Abstract: We report a detailed investigation of the magnetocaloric properties of self-doped polycrystalline LaMnO3+δ with δ = 0.04. Due to the self-doping effect, the system exhibits a magnetic transition from a paramagnetic to ferromagnetic-like canted magnetic state (CMS) at ∼120 K, which is associated with an appreciably large magnetocaloric effect (MCE). The CMS is an inhomogeneous magnetic phase developing due to a steady growth of antiferromagnetic correlation in its predominant ferromagnetic state below ∼120 K. The stabilization of CMS in this material is concluded from a comprehensive analysis of magnetocaloric data using Landau theory, which is in excellent agreement with our neutron diffraction study. The magnetic entropy change versus temperature curves for different applied fields collapse into a single curve, revealing a universal behavior of MCE. Our studies suggest that investigation of MCE is an effective technique to acquire fundamental understanding about the basic magnetic structure of a system with complex competing interactions.
TL;DR: In this article, the magnetic properties of La0.8Sr0.2Fe1−xCuxO3−w compounds were analyzed at room temperature with the neutron powder diffraction technique and the Rietveld method of profile fitting.
TL;DR: In this article, first principles density functional theory DFT+U calculations and experimental neutron diffraction structure analyses were used to determine the low-temperature crystallographic and magnetic structure of bixbyite Mn2O3.
Abstract: First principles density functional theory DFT+U calculations and experimental neutron diffraction structure analyses were used to determine the low-temperature crystallographic and magnetic structure of bixbyite Mn2O3. The energies of various magnetic arrangements, calculated from first principles, were fit to a cluster-expansion model using a Bayesian method that overcomes a problem of underfitting caused by the limited number of input magnetic configurations. The model was used to predict the lowest-energy magnetic states. Experimental determination of magnetic structure benefited from optimized sample synthesis, which produced crystallite sizes large enough to yield a clear splitting of peaks in the neutron powder diffraction patterns, thereby enabling magnetic-structure refinements under the correct orthorhombic symmetry. The refinements employed group theory to constrain magnetic models. Computational and experimental analyses independently converged to similar ground states, with identical antiferromagnetic ordering along a principal magnetic axis and secondary ordering along a single orthogonal axis, differing only by a phase factor in the modulation patterns. The lowest-energy magnetic states are compromise solutions to frustrated antiferromagnetic interactions between certain corner-sharing MnO6 octahedra.
TL;DR: The effect of strontium substitution on structural, magnetic, and dielectric properties of a multiferroic Y-type hexaferrite (chemical formula Ba2−xSrxMg2Fe12O22 with 0.
Abstract: The effect of strontium substitution on structural, magnetic, and dielectric properties of a multiferroic Y-type hexaferrite (chemical formula Ba2−xSrxMg2Fe12O22 with 0 ≤ x ≤ 2) was investigated. Y-type hexaferrite phase formation was not affected by strontium substitution for barium, in the range 0 ≤ x ≤ 1.5, confirmed by x-ray diffraction and Raman spectroscopy measured at room temperature. Two intermediate magnetic spin phase transitions (at tempertures TI and TII) and a ferrimagnetic-paramagnetic transition (at Curie temperature TC) were identified from the temperature dependence of the magnetic susceptibility. Magnetic transition temperatures (TI, TII, and TC) increased with increasing strontium content. Magnetic hysteresis measurements indicated that by increasing strontium concentration, the coercivity increases, while the saturation magnetization decreases. The 57Fe NMR spectrum of the Y-type hexaferrite measured at 5 K and in zero magnetic field showed remarkable differences compared to that of o...
TL;DR: In this article, a growth rate of La(FexSi1−x)13 phase against homogenization is governed by reaction diffusion, and the volume dependence of the Curie temperature after hydrogenation elucidates the role of the magnetovolume effect.
TL;DR: In this paper, the spin-flop transition in the magnetoelectric quasi-2D Heisenberg system LiMnPO${}_{4}$ is studied in fields applied along the $a$ axis.
Abstract: The nature of the spin-flop (SF) transition in the magnetoelectric quasi-2D Heisenberg system LiMnPO${}_{4}$ is studied in fields applied along the $a$ axis. A refinement of the magnetic structure using neutron diffraction data in the SF phase reveals that the spins reorient from being parallel to the $a$ axis to be nearly along the $c$ axis at magnetic fields between 4 and 4.7 T, depending on temperature. The low-field antiferromagnetic phase boundary is shown to join the spin-flop line tangentially at the so-called bicritical point, where there is a suppression of the ordering temperature. At the bicritical field, we observe an increased intensity of the Lorentz broadened elastic scattering at magnetic Bragg peaks above ${T}_{N}$ as compared to zero field and 10 T, without an increase in peak width. This suggests an increased density of fluctuations at the bicritical field as compared to zero field.
TL;DR: Using density functional theory (DFT), Hartree-Fock, exact diagonalization, and numerical-renormalization-group methods, the electronic structure of diluted hydrogen atoms chemisorbed on graphene was studied in this article.
Abstract: Using density-functional-theory (DFT), Hartree-Fock, exact-diagonalization, and numerical-renormalization-group methods, we study the electronic structure of diluted hydrogen atoms chemisorbed on graphene. A comparison between DFT and Hartree-Fock calculations allows us to identify the main characteristics of the magnetic structure of the defect. We use this information to formulate an Anderson-Hubbard model that captures the main physical ingredients of the system while still allowing a rigorous treatment of the electronic correlations. We find that the large hydrogen-carbon hybridization puts the structure of the defect halfway between the one corresponding to an adatom weakly coupled to pristine graphene and that of a carbon vacancy. The impurity's magnetic moment leaks into the graphene layer where the electronic correlations on the C atoms play an important role in stabilizing the magnetic solution. Finally, we discuss the implications for the Kondo effect.
TL;DR: This study demonstrates how multicomponent magnetic structures found in magnetically frustrated materials like Mn(2)GeO(4) provide a new route towards functional materials that exhibit coupled ferromagnetism and ferroelectricity.
Abstract: The olivine compound Mn2GeO4 is shown to feature both a ferroelectric polarization and a ferromagnetic magnetization that are directly coupled and point along the same direction. We show that a spin spiral generates ferroelectricity, and a canted commensurate order leads to weak ferromagnetism. Symmetry suggests that the direct coupling between the ferromagnetism and ferroelectricity is mediated by Dzyaloshinskii-Moriya interactions that exist only in the ferroelectric phase, controlling both the sense of the spiral rotation and the canting of the commensurate structure. Our study demonstrates how multicomponent magnetic structures found in magnetically frustrated materials like Mn2GeO4 provide a new route towards functional materials that exhibit coupled ferromagnetism and ferroelectricity.
TL;DR: A structural symmetric breaking from the rhombohedral R3c to orthorhombic Pnma at around x=0.10 was identified across a ferroelectric-paraelectric phase as discussed by the authors.
TL;DR: In this article, the magnetic motif of the Eu ions in magnetoelectric EuTiO${}_{3}$ was examined using neutron powder diffraction and x-ray single-crystal magnetic diffraction.
Abstract: We combine neutron powder diffraction and x-ray single-crystal magnetic diffraction at the Eu $L$${}_{2}$ edge to scrutinize the magnetic motif of the Eu ions in magnetoelectric EuTiO${}_{3}$. Our measurements are consistent with an antiferromagnetic $G$-type pattern with the Eu magnetic moments ordering along the $a,b\phantom{\rule{0.16em}{0ex}}$-plane diagonal. Recent reports of a novel transition at 2.75 K with a flop of magnetic moments upon poling the sample in an electric field cannot be confirmed for a nonpoled sample. Our neutron diffraction data do not show any significant change of the structure below the N\'eel temperature. Magnetoelastic coupling, if present, is therefore expected to be negligible.
TL;DR: The azimuthal and polarization dependence of the magnetic reflections, relating to both magnetic wavevectors, show that the Ir magnetic moments in the bilayer compound are oriented along the c axis, which contrasts with single layer Sr(2)IrO(4) where the moments are confined to the ab plane.
Abstract: This report presents azimuthal dependent and polarization dependent x-ray resonant magnetic scattering at the Ir L3 edge for the bilayered iridate compound Sr3Ir2O7. The two magnetic wave vectors, and , result in domains of two symmetry-related G-type antiferromagnetic structures, denoted A and B, respectively. These domains are approximately 0.02 mm2 and are independent of the thermal history. An understanding of this key aspect of the magnetism is necessary for an overall picture of the magnetic behaviour in this compound. The azimuthal and polarization dependence of the magnetic reflections, relating to both magnetic wavevectors, show that the Ir magnetic moments in the bilayer compound are oriented along the c axis. This contrasts with single layer Sr2IrO4 where the moments are confined to the ab plane.
TL;DR: In this paper, the magnetic properties of monoclinic CoVs were investigated by powder neutron diffraction measurements and ab initio calculations and they were successfully related to a theoretical model.
Abstract: In this work, we investigate the magnetic properties of the monoclinic $\ensuremath{\alpha}$-CoV${}_{2}$O${}_{6}$ by powder neutron diffraction measurements and ab initio calculations. An emphasis has been pointed towards the magnetic structure and the interaction between the Co ions leading to magnetic frustrations in this compound. Neutron diffraction experiments were carried out both in the ground state (zero magnetic field) and under applied external field of 2.5 and 5 T corresponding to the ferrimagnetic and ferromagnetic states, respectively. The antiferromagnetic ground state below 14 K corresponds to $k=(1,0,\frac{1}{2})$ magnetic propagation vector in $C1$ space group. The magnetic structure can be described by ferromagnetic interactions along the chains ($b$ axis) and antiferromagnetic coupling between the chains (along $a$ and $c$ axes). The ferrimagnetic structure implies a ninefold unit cell (3a, b, 3c) in which ferromagnetic chains follow an ``up-up-down'' sequence along the $a$ and $c$ axes. In the ferromagnetic state, the spin orientations remain unchanged while every chain lies ferromagnetically ordered. In all cases, the magnetic moments lie in the $ac$ plane, along the CoO${}_{6}$ octahedra axis, at an angle of 9.3${}^{\ensuremath{\circ}}$ with respect to the $c$ axis. The magnetic structure of $\ensuremath{\alpha}$-CoV${}_{2}$O${}_{6}$ resolved for all the ordered states is successfully related to a theoretical model. Ab initio calculations allowed us to (i) confirm the ground-state magnetic structure, (ii) calculate the interactions between the Co ions, (iii) explain the frustration leading to the stepped variation of the magnetization curves, (iv) calculate the orbital magnetic moment (1.5 ${\ensuremath{\mu}}_{B}$) on Co atoms, and (v) confirm the direction of the magnetic moments near the $c$ direction.