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Magnetic structure
About: Magnetic structure is a research topic. Over the lifetime, 10787 publications have been published within this topic receiving 207143 citations.
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TL;DR: The compounds Ba2LnMoO6, Sm, Eu, Gd, Dy, Y, Er, and Yb have been synthesized by solid-state techniques under reducing conditions at temperatures up to 1300 °C.
Abstract: The compounds Ba2LnMoO6 (Ln ) Nd, Sm, Eu, Gd, Dy, Y, Er, and Yb) have been synthesized by solid-state techniques under reducing conditions at temperatures up to 1300 °C. Rietveld analyses of X-ray and neutron powder diffraction data show that these compounds adopt cation-ordered perovskite phases. At room temperature Ba2NdMoO6 and Ba2SmMoO6 adopt tetragonally distorted structures in the space groups I4/m and I4/mmm, respectively, while the data collected from all other compounds could be fitted in the cubic space group Fm3hm. Bond valence sums show that the observed tetragonal distortions are driven by the bonding requirements of Ba2+. Neutron powder diffraction data collected below TN ) 15(1) K show that Ba2NdMoO6 is triclinically distorted (I1h: a ) 5.9790(2) A, b ) 5.9840(2) A, c ) 8.6024(2) A, R ) 89.854(2)°, â ) 90.056(5)°, c ) 90.003(5)°) and that Nd3+ and Mo5+ are antiferromagnetically ordered. Magnetic susceptibility data show that this compound behaves as a Curie- Weiss paramagnet above this temperature, and no other compounds in the series show evidence of magnetic order down to 2 K. Ba2YMoO6 and Ba2YbMoO6 both remain entirely paramagnetic to 2 K due to perfect geometric frustration of the cubic lattice, indicating that next-nearest-neighbor interactions between like cations dominate over nearest-neighbor Mo-O-Ln exchange. The magnetic structure of Ba2NdMoO6 is rationalized with reference to the splitting of the t2g manifold of Mo5+ by the Jahn-Teller distortion and the associated introduction of anisotropic magnetic superexchange.
52 citations
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.
52 citations
TL;DR: The perovskite lattices contain an almost completely ordered array of CoO6 and TeO6 octahedra, which is associated with the tilting angles as mentioned in this paper.
Abstract: Ca2CoTeO6 and Sr2CoTeO6 double perovskites have been prepared as polycrystalline powders by solid state reaction, in air. These materials have been studied by X-ray, neutron powder diffraction (NPD) and magnetic measurements. At room temperature, the crystal structure is monoclinic, space group P21/n for both compounds with a
= 5.4569(2)
A, b
= 5.5904(2)
A, c
= 7.7399(2)
A, β
= 90.239(2)° and a
= 5.6417(2)
A, b
= 5.6063(2)
A, c= 7.9234(2)
A, β
= 90.117(4)° for Ca2CoTeO6 and Sr2CoTeO6 respectively. The perovskite lattices contain an almost completely ordered array of CoO6 and TeO6 octahedra. The monoclinic distortion is larger in Ca2CoTeO6 than in Sr2CoTeO6, which is associated with the tilting of the CoO6 and TeO6 octahedra, displaying tilting angles φ
= 4.8° for Sr2CoTeO6 and φ
= 15.1° for Ca2CoTeO6. The low temperature magnetic structures were determined by NPD, selected among the possible magnetic solutions compatible with the P21/n space group, according with the group theory representation. The propagation vectors for the Ca and Sr compounds are k
= 0 and k
=
(½, ½, 0), respectively. A canted antiferromagnetic structure is observed for Ca2CoTeO6 below TN
= 10 K, which remains stable down to 2.2 K, with an ordered magnetic moment of 2.37(3)
μB for Co2+ cations. For Sr2CoTeO6, an antiferromagnetic ordering is displayed below TN
= 15 K, that remains stable down to 2.9 K, with an ordered magnetic moment for Co2+ of 2.15(4)
μB.
52 citations
TL;DR: In this paper, the authors performed x-ray diffraction experiments at the L absorption edges for the post-perovskite-type compound CaIrO(3) with a (t(2g))^{5} electronic configuration and showed that the magnetic structure was a striped ordering with an antiferromagnetic moment along the c axis.
Abstract: We performed resonant x-ray diffraction experiments at the L absorption edges for the post-perovskite-type compound CaIrO(3) with a (t(2g))^{5} electronic configuration. By observing the magnetic signals, we could clearly see that the magnetic structure was a striped ordering with an antiferromagnetic moment along the c axis and that the wave function of a t(2g) hole is strongly spin-orbit entangled, the J(eff)=1/2 state. The observed spin arrangement is consistent with theoretical work predicting a unique superexchange interaction in the J(eff)=1/2 state and points to the universal importance of the spin-orbit coupling in Ir oxides, independent of the octahedral connectivity and lattice topology. We also propose that nonmagnetic resonant scattering is a powerful tool for unraveling an orbital state even in a metallic iridate.
52 citations
TL;DR: In this paper, the magnetic susceptibility of NiI2 and CoI2 was measured with X-ray and neutron diffraction and the nuclear and magnetic structures were examined with Xray and Neutron diffraction with an anisotropic behavior and a magnetic ordering temperature of 75 K.
Abstract: Measurements of the magnetic susceptibility of NiI2 show an anisotropic behaviour and a magnetic ordering temperature of 75 K The nuclear and magnetic structures are examined with X-ray and neutron diffraction The nuclear symmetry changes at 60 K from trigonal to monoclinic The magnetic structure of NiI2 is an incommensurate helix of type 1, with propagation vector Q x =01384 a ∗ ; Q y =0; Q z =1457 c ∗ The anisotropy of the magnetic susceptibility of CoI 2 is due to single-ion anisotropy The magnetic structure is a commensurate helix of type 1, with Q x = 1 8 a ∗ ; Q y =0; Q z 1 2 c ∗ 129I-Mossbauer data of NiI2 and CoI2 are in good agreement with the paoposed magnetic structures The stability of magnetic structures in trigonal layer compounds is discussed It is found that the structures of CoI2 and NiI2 are close to the phase boundary between helix-1 type structures and structures with ferromagnetic layers
52 citations