Magnetic structure

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

Low temperature magnetic properties of geometrically frustrated Gd2Sn2O7 and Gd2Ti2O7

Abstract: We have examined the low temperature magnetic properties of the geometrically frustrated antiferromagnetic pyrochlores Gd2Sn2O7 and Gd2Ti2O7 using specific heat, 155Gd M?ssbauer, magnetic susceptibility and magnetization measurements. For Gd2Sn2O7, the specific heat evidences a single, strongly first order magnetic transition near 1.0?K; in Gd2Ti2O7, we confirm the presence of both the transition near 1.0?K and the second transition near 0.75?K. Below 1?K, magnetic irreversibilities are present in both compounds, but their signature (the difference between the FC and ZFC branches) is more marked in Gd2Sn2O7. At 0.03?K in each compound, the M?ssbauer data show that the four Gd3+ of a tetrahedron carry moments of equal sizes and on a frequency scale of 120 ? 106?s?1 each is oriented perpendicular to the local direction. In Gd2Ti2O7, the M?ssbauer data also indicates that the transition at 0.75?K involves a small change in the magnetic structure.

Various magnetic domain structures in a Ni–Mn–Ga martensite exhibiting magnetic shape memory effect

Abstract: Magnetic domain structures of the Ni–Mn–Ga martensite were observed by means of type I and type II magnetic contrast in scanning electron microscope. The different configuration of magnetic domain patterns coupled together with the twin structures were studied in multivariant, two-variant, and single-variant martensite. The martensitic band contains broad stripelike magnetic domains following the easy axis of magnetization, i.e., the crystallographic c axis. These stripe domains are connected by 90° domain walls creating a staircaselike structure in the adjoining bands. It is found that the internal twins, substructures of the martensite twin domains, are distorted into a zig–zag shape in order to accommodate the main band magnetization. Furthermore, the dagger-shaped stripe domains occur only when the internal twins are present. When the sample exhibits the single-variant state, the internal twins disappear totally and the stripe magnetic domains spread over the whole specimen. The configuration observed here for the magnetic microstructure together with the crystallographic microstructure can help in understanding the magnetic shape memory effect.

Electronic and magnetic structure of infinite-layer NdNiO2: trace of antiferromagnetic metal

Abstract: The recent discovery of Sr-doped infinite-layer nickelate NdNiO2 offers a new platform for investigating unconventional superconductivity in nickelate-based compounds. Most intriguingly, the resistivity minimum and Hall coefficient drop were identified simultaneously in the experiment, reflecting a novel electronic structure and transport property of NdNiO2. Driven by this pioneering work, we present a first-principles calculation for the electronic and magnetic structure of undoped parent NdNiO2. By taking into account experimentally relevant interaction strength, we found that (π, π, π) antiferromagnetic NdNiO2 is a compensated bad metal with small Fermi pockets. However, due to the small exchange coupling between 3d-electrons of Ni and strong hybridization with 5d-electrons of Nd, the discovered antiferromagnetic ordering is very weak. Crucially, with the decreasing of temperature, there exists a phase transition between good paramagnetic metal and bad AFM metal. The estimated transition temperature is ~70–90 K, which is consistent with that for observing the resistivity minimum and Hall coefficient drop. In this regarding, our results provide a plausible physical interpretation for these significant experimental observations.

Magnetic field structure around low-mass class 0 protostars: b335, l1527, and ic348-smm2

Abstract: We report new 350 μm polarization observations of the thermal dust emission from the cores surrounding the low-mass, Class 0 young stellar objects L1527, IC348-SMM2, and B335. We have inferred magnetic field directions from these observations and have used them together with results in the literature to determine whether magnetically regulated core-collapse and star formation models are consistent with the observations. These models predict a pseudo-disk with its symmetry axis aligned with the core magnetic field. The models also predict a magnetic field pinch structure on a scale less than or comparable to the infall radii for these sources. In addition, if the core magnetic field aligns (or nearly aligns) the core rotation axis with the magnetic field before core collapse, then the models predict the alignment (or near alignment) of the overall pinch field structure with the bipolar outflows in these sources. We show that if one includes the distorting effects of bipolar outflows on magnetic fields, then in general the observational results for L1527 and IC348-SMM2 are consistent with these magnetically regulated models. We can say the same for B335 only if we assume that the distorting effects of the bipolar outflow on the magnetic fields within the B335 core are much greater than for L1527 and IC348-SMM2. We show that the energy densities of the outflows in all three sources are large enough to distort the magnetic fields predicted by magnetically regulated models.