Magnetic structure

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

Chemical and magnetic order in platinum-rich Pt + Fe alloys

Abstract: Neutron-diffraction and direct magnetic measurements have been used to determine the magnetic structures of platinum + iron alloys in the neighbourhood of the composition Pt 3 Fe It is found that the magnetic structure is sensitively dependent on the precise chemical order, in particular on the number of nearest-neighbour iron atoms Alloys of the stoichiometric composition, where the chemical order is perfect, have a simple antiferromagnetic structure, but addition of excess iron leads to the coexistence of two different structures, with different Neel temperatures but a single, undistorted, cubic unit cell An incipient ferromagnetic state which shows a cluster type of behaviour is associated with the presence of excess iron Increase of iron content beyond 34 % leads to the growth of bulk ferromagnetism Throughout the sequence of structural changes the iron atoms carry a magnetic moment of about 33 μ B and there appears to be very little alined moment on the platinum atoms

Current-induced rotational torques in the skyrmion lattice phase of chiral magnets

Abstract: In chiral magnets without inversion symmetry, the magnetic structure can form a lattice of magnetic whirl lines, a two-dimensional skyrmion lattice, stabilized by spin-orbit interactions in a small range of temperatures and magnetic fields. The twist of the magnetization within this phase gives rise to an efficient coupling of macroscopic magnetic domains to spin currents. We analyze the resulting spin-transfer effects, and, in particular, focus on the current-induced rotation of the magnetic texture by an angle. Such a rotation can arise from macroscopic temperature gradients in the system as has recently been shown experimentally and theoretically. Here we investigate an alternative mechanism, where small distortions of the skyrmion lattice and the transfer of angular momentum to the underlying atomic lattice play the key role. We employ the Landau-Lifshitz-Gilbert equation and adapt the Thiele method to derive an effective equation of motion for the rotational degree of freedom. We discuss the dependence of the rotation angle on the orientation of the applied magnetic field and the distance to the phase transition.

A twisted flux rope as the magnetic structure of a filament in active region 10953 observed by hinode

Abstract: The presence of twisted flux ropes (TFRs) in pre-eruptive/flaring magnetic configurations is of main interest for our understanding of the structure and dynamics of the solar corona. On the one hand, their presence is a key ingredient in several theoretical models for the magnetic support of material in filaments, or triggering of coronal mass ejections as well as the emergence of structures from the convection zone into the corona. On the other hand, several observations have shown the presence of twist and shear during eruptive and flaring phases of eruptive phenomena. In this paper, we consider the determination of the magnetic structure of active region (AR) 10953 observed by Hinode and reconstructed using our two nonlinear force-free models. We show that the reconstructed magnetic configurations exhibit a TFR along the southern part of the neutral line. Moreover, the location of the magnetic dips within the TFR agrees within a good level of accuracy with the Hα images taken by SMART and the vertically integrated current density recovers the main structure present in Hinode/XRT images. The free magnetic energy is also found to be large enough to power the two C-class flares of the following days. We finally compare our results with those of Su et al. who proposed an interesting model of the same AR in which a TFR is inserted at the same location using the flux rope insertion method.