Magnetic structure

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

Magnetic Structure of MnAs and MnAs0·92P0·08

Abstract: The similarity of the ordered magnetic structures of orthorhombic MnAs (stable at high pressure) and orthorhombic MnAs0.92P0.08 has been confirmed using neutron diffraction. Below the magnetic ordering temperature, Tc, a canted spin structure is found for both materials. Neutron diffraction measurements from magnetically ordered and disordered temperature regions show that in these materials the Mn magnetic moment varies with the volume of the Mn atom. The variation of the magnitude of the Mn magnetic moment is explained using the relation between Pauling valence and magnetic moment introduced by Mori and Mitsui. The results are in disagreement with the currently accepted interpretation of the susceptibility data.

NEUTRON DIFFRACTION STUDY OF THE MAGNETIC PROPERTIES OF MnBr$sub 2$

Abstract: The antiferromagnetic structure of MnBr/sub 2/ (T/sub N/ = 2.16 deg K) has been determined by single-crystal neutron diffraction measurements nt temperatures down to 1.35 deg K and with magnetic fields (0-- 13 kilo-oersteds) applied to the sample. The antiferromsgnetic structure appeared to have hexagonal symmetry in the absence of a magnetic field but this was found to be associated with a structure domain-growth property. The true magnetic structure was found to be associated with one or another of three hexsgonal axes, the particular growth direction being determined by the direction of an applied magnetic field. Information relating to indirect magnetic exchange via the bromine ions in this crystal was obtained from a study of the domain growth properties. The antiferromagnetic ordering transition in this compound was found to be nearly first order rather than of the usual second order type. A small lowering (~2%) of T/sub N/ was observed for an applied field of 13.1 kolooersteds. Short-range order data were obtained from powder patterns. (auth)

Structural phase transitions and magnetic order in SrTcO3

Abstract: The structure of the perovskite SrTcO(3) has been investigated using both synchrotron X-ray and neutron powder diffraction. At room temperature SrTcO(3) is orthorhombic as a consequence of cooperative tilting of the corner sharing TcO(6) octahedra. The tilts are sequentially removed as the sample is heated with the oxide displaying the sequence of structres Pnma→Imma→I4/mcm→Pm 3m. Neutron powder diffraction data collected in the temperature range 4-1023 K indicate that SrTcO(3) has G-type antiferromagnetic structure, in which each Tc moment is antiparallel to its six nearest neighbours, below ∼1000 K. The magnetic structure is collinear antiferromagnetic with the technetium moments parallel to c-axis and can be described by the propagation vector k = [0,0,0] and the basis vector (0,0,A(z)). The same magnetic structure is observed in each of the four crystal structures.

Origin of a magnetic easy axis in pipeline steel

Abstract: Oil and gas pipelines are generally magnetically anisotropic, with a magnetic easy axis in the pipe axial direction. This is of interest because magnetic flux leakage tools are commonly used for the detection and sizing of defects. In the present study we investigate the origin of this magnetic easy axis, using an angular magnetic Barkhausen noise technique to characterize the magnetic anisotropy. The texture, microstructure, and residual stress are examined as possible causes of the easy axis, using x-ray pole figure analysis and microstructural examination along with high and low temperature annealing treatments. Our results indicate that plastic deformation and residual stress are responsible for the magnetic easy axis, since an elimination of the residual stresses through low temperature “stress relief” heat treatment produces a magnetically isotropic structure without altering the texture or microstructure. X-ray pole figure analysis supports the conclusion that magnetic anisotropy is not related to texture in these materials. We conclude that the axial magnetic easy axis is due to a compressive residual hoop stress resulting from the cold bending and cold expansion of the pipe during processing.