Magnetic structure

About: Magnetic structure is a research topic. Over the lifetime, 10787 publications have been published within this topic receiving 207143 citations.

Polarized neutron diffraction and Mössbauer-effect study of the magnetic ordering in Wüstite, FeyO

Abstract: Maintien de l'ordre antiferromagnetique au voisinage des amas de defauts, avec modifications de la direction de spin, d'apres les mesures de diffraction de neutrons a 45 K (structure de spin a peu pres colineaire au niveau local). Analyse des spectres Mossbauer tres complexes (a 4,2 et 78 K): un sextriplet hyperfin de Fe(III), deux sextriplets hyperfins de Fe(II), un doublet quadripolaire de Fe(III)

Magnetic excitations in non-collinear antiferromagnetic Weyl semimetal Mn 3 Sn

Abstract: Mn3Sn has recently attracted considerable attention as a magnetic Weyl semimetal exhibiting concomitant transport anomalies at room temperature. The topology of the electronic bands, their relation to the magnetic ground state and their nonzero Berry curvature lie at the heart of the problem. The examination of the full magnetic Hamiltonian reveals otherwise hidden aspects of these unusual physical properties. Here, we report the full spin wave spectra of Mn3Sn measured over a wide momentum—energy range by the inelastic neutron scattering technique. Using a linear spin wave theory, we determine a suitable magnetic Hamiltonian which not only explains the experimental results but also stabilizes the low-temperature helical phase, consistent with our DFT calculations. The effect of this helical ordering on topological band structures is further examined using a tight binding method, which confirms the elimination of Weyl points in the helical phase. Our work provides a rare example of the intimate coupling between the electronic and spin degrees of freedom for a magnetic Weyl semimetal system. The interplay between the electronic and spin degrees of freedom determines the removal of Weyl points in magnetic semimetal systems. A team led by Je-Geun Park at the Institute for Basic Science and Seoul National University used linear spin wave theory to obtain the full spin wave spectra of antiferromagnetic A-type Mn3Sn across a broad energy-momentum range. The magnetic Hamiltonian obtained via a local moment model was capable of explaining the experimental inelastic neutron scattering data. Additional density functional theory calculations indicated that the Mn3Sn low-temperature magnetic structure involves a helical ordering that eliminates the Weyl points, and consequently reduces Mn3Sn experimental anomalous Hall conductivity. These results indicate how topological Weyl points can be removed by introducing a minor change to the magnetic ground state.

Asphericity in the magnetization distribution of holmium

Abstract: In a spiral magnetic structure an aspherical magnetic moment distribution around the ions gives rise to a new set of diffraction lines indexed as third-order satellites. Neutron-diffraction measurements have been made on single crystals of holmium and a ${\mathrm{Ho}}_{0.9}$${\mathrm{Sc}}_{0.1}$ alloy to determine the magnetic structures as a function of temperature, and measure the intensities of the third-order satellites. From these intensities the experimental asphericity of the magnetization density is compared to that calculated with a single-ion model. The agreement between theory and experiment is qualitative; the experimental intensities being larger by a factor of \ensuremath{\sim} 1.5. The temperature dependence of the third-order satellite is in good agreement with a simple model proposing exchange splitting of the free-ion multiplet, with a negligible crystal-field interaction.

The static, paramagnetic, spin susceptibility of metals at finite temperatures

Abstract: The authors present a theory for the static, paramagnetic, spin susceptibility for metals at finite temperatures. It is based on a 'first principles' mean-field theory of itinerant magnetism and provides an expression which resembles that of a classical Heisenberg model added to an itinerant component. The quantities which occur in this expression all depend on the underlying electronic structure of the disordered local moment (DLM) paramagnetic state and thus demonstrate the subtle combination of the localised and itinerant aspects of this problem. The theory is applied to BCC iron and FCC nickel. A Curie temperature of 1280K and effective Curie constant moment of 1.97 mu B is obtained for iron in reasonable agreement with experiment. From the calculations of the wavevector dependent susceptibility, which are compared with quasi-elastic neutron scattering data, equal time spatial, magnetic correlation functions are inferred which are consistent with the magnetic structure of the initially imposed (DLM) paramagnetic state. The calculations for nickel provide a very different picture. At temperatures at which the DLM paramagnetic state differs from the conventional 'Stoner' state, it is shown that this state is unstable via the sensitivity of the moments to their orientational environment and that the theory for the paramagnetic state is equivalent to that of the Stoner-Wohlfarth picture. It is concluded that an improved theory for nickel must incorporate a mechanism for 'local' moment formation on several sites.