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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: In this article, the results of an LDA and LDA+U band structure study of the monoclinic and the corundum phases of V2O3 were presented.
Abstract: We present the results of an LDA and LDA+U band structure study of the monoclinic and the corundum phases of V2O3 and argue that the most prominent (spin 1/2) models used to describe the semiconductor metal transition are not valid. Contrary to the generally accepted assumptions we find that the large on site Coulomb and exchange interactions result in a total local spin of 1 rather than 1/2 and especially an orbital occupation which removes the orbital degeneracies and the freedom for orbital ordering. The calculated exchange interaction parameters lead to a magnetic structure consistent with experiment again without the need of orbital ordering. While the low-temperature monoclinic distortion of the corundum crystal structure produces a very small effect on electronic structure of v2o3, the change of magnetic order leads to drastic differences in band widths and band gaps. The low temperature monoclinic phase clearly favors the experimentally observed magnetic structure, but calculations for corundum crystal structure gave two consistent sets of exchange interaction parameters with nearly degenerate total energies suggesting a kind of frustration in the paramagnetic phase. These results strongly suggest that the phase transitions in V2O3 which is so often quoted as the example of a S=1/2 Mott Hubbard system have a different origin. So back to the drawing board!
101 citations
TL;DR: The magnetic and crystallographic structures of the alloys Pd2MnIn, Pd 2MnSn and Pd 1MnSb are described in this paper.
Abstract: The magnetic and crystallographic structures of the alloys Pd2MnIn, Pd2MnSn and Pd2MnSb are described. The three alloys are shown to have the Heusler (L21) structure, and to exhibit magnetic order. Pd2MnIn can be obtained in ordered and partially disordered forms by suitable heat treatment. The ordered alloy is anti-ferromagnetic with a Neel temperature of 142°K. The magnetic structure has been determined from neutron diffraction measurements. The magnetic moments of 4·3 μB are confined to the Mn atoms, which are aligned in ferromagnetic (111) planes, with neighbouring planes oriented antiparallel as in NiO. In the partially disordered alloy most of the former anti-ferromagnetic order is destroyed along with the chemical order, but is replaced by anti-ferromagnetic order on a magnetic unit cell half the original size. The structures of Pd2MnSn and Pd2MnSb are insensitive to heat treatment. Both alloys are ordered, and ferromagnetic, with the magnetic moments residing on the Mn atoms. The Pd2MnSn ...
101 citations
TL;DR: In this article, the spin liquid Tb$_2$Sn$_ 2$O$_7$ by neutron diffraction and specific heat measurements was studied and a new magnetic structure was observed, not predicted by current models, with both ferromagnetic and antiferromagnetic character.
Abstract: We have studied the spin liquid Tb$_2$Sn$_2$O$_7$ by neutron diffraction and specific heat measurements. Below about 2 K, the magnetic correlations change from antiferromagnetic to ferromagnetic. Magnetic order settles in two steps, with a smeared transition at 1.3(1) K then an abrupt transition at 0.87(2) K. A new magnetic structure is observed, not predicted by current models, with both ferromagnetic and antiferromagnetic character. It suggests that the spin liquid degeneracy is lifted by dipolar interactions combined with a finite anisotropy along $ $ axes. In the ground state, the Tb$^{3+}$ ordered moment is reduced with respect to the free ion moment (9 $\mu_{\rm B}$). The moment value of 3.3(3) $\mu_{\rm B}$ deduced from the specific heat is much smaller than derived from neutron diffraction of 5.9(1) $\mu_{\rm B}$. This difference is interpreted by the persistence of slow collective magnetic fluctuations down to the lowest temperatures.
100 citations
TL;DR: In this paper, the static structure factor in the two-dimensional spinS = 1/2 square-lattice Heisenberg antiferromagnet Sr2CuO2Cl2 was investigated.
Abstract: We have carried out a neutron scattering investigation of the static structure factorS(q
2D
) (q
2D
is the in-plane wave vector) in the two-dimensional spinS=1/2 square-lattice Heisenberg antiferromagnet Sr2CuO2Cl2. For the spin correlation length ξ we find quantitative agreement with Monte Carlo results over a wide range of temperature. The combined Sr2CuO2Cl2-Monte Carlo data, which cover the length scale from ≈1 to 200 lattice constants, are predicted without adjustable parameteres by renormalized classical theory for the quantum nonlinear sigma model. For the structure factor peakS(0), on the other hand, we findS(0)∼ξ
2 for the reduced temperature range 0.16
100 citations
TL;DR: In this article, the element and size-dependent electron stability of Aun M+ clusters (M=Sc, Ti, V, Cr, Mn, Fe, Au; n ≥ 9) was investigated by means of first-principles density functional calculations.
Abstract: We investigate the element- and size-dependent electron stability of Aun M+ clusters (M=Sc, Ti, V, Cr, Mn, Fe, Au; n≤9) by means of first-principles density functional calculations. The interplay between the cluster atomic arrangements and their electronic and magnetic structure is studied for the few lowest energy isomeric states and their dependence on the dopant atom and its environment in the host cluster. Our total energy calculations provide a clear explanation of the abundance peaks observed recently in photofragmentation experiments. The magnetic and geometrical configurations are strongly correlated. The local magnetic moment of the dopant atom shows a pronounced odd-even oscillation with the number of Au atoms, and decreases when the cluster size increases. © 2005 The American Physical Society.
100 citations