Non-quasiparticle states in Co2_2MnSi evidenced through magnetic tunnel junction spectroscopy measurements

We investigate the effects of electronic correlations in the full-Heusler Co$_2$MnSi, by combining a theoretical analysis of the spin-resolved density of states with tunneling-conductance spectroscopy measurements using Co$_2$MnSi as electrode. Both experimental and theoretical results confirm the existence of so-called non-quasiparticle states and their crucial contribution to the finite-temperature spin polarisation in this material.Comment: Repalced Fig. 1. of PRL, 100, 086402 (2008), better k-space resolution for DOS around Fermi energ

Theory of current-driven motion of Skyrmions and spirals in helical magnets

We study theoretically the dynamics of the spin textures, i.e., Skyrmion crystal (SkX) and spiral structure (SS), in two-dimensional helical magnets under external current. By numerically solving the Landau-Lifshitz-Gilbert equation, it is found that (i) the critical current density of the motion is much lower for SkX compared with SS in agreement with the recent experiment, (ii) there is no intrinsic pinning effect for SkX and the deformation of the internal structure of Skyrmion reduces the pinning effect dramatically, (iii) the Bragg intensity of SkX shows strong time-dependence as can be observed by neutron scattering experiment.Comment: 4 pages, 3 figure

Interfacial structure and half-metallic ferromagnetism in Co2MnSi-based magnetic tunnel junctions

Copyright © 2006 The American Physical SocietyX-ray absorption (XAS) and x-ray magnetic circular dichroism (XMCD) techniques are utilized to explore the ferromagnetic/barrier interface in Co2MnSi full Heusler alloy magnetic tunnel junctions. Structural and magnetic properties of the interface region are studied as a function of the degree of site disorder in the alloy and for different degrees of barrier oxidation. Photoelectron scattering features that depend upon the degree of L2(1) ordering are observed in the XAS spectra. Additionally, the moments per 3d hole for Co and Mn atoms are found to be a sensitive function of both the degree of L2(1) ordering and the barrier oxidation state. Significantly, a multiplet structure is observed in the XMCD spectra that indicates a degree of localization of the moments and may result from the half-metallic ferromagnetism (HMF) in the alloy. The magnitude of this multiplet structure appears to vary with preparation conditions and could be utilized to ascertain the role of the constituent atoms in producing the HMF, and to examine methods for preserving the half-metallic state after barrier preparation. The changes in the magnetic structure caused by barrier oxidation could be reversed by inserting a thin Mg interface layer in order to suppress the oxidation of Mn in the Co2MnSi layer

Temperature dependence of the interface moments in Co2MnSi thin films

Copyright © 2008 American Institute of PhysicsX-ray magnetic circular dichroism (XMCD) is utilized to explore the temperature dependence of the interface moments in Co2MnSi (CMS) thin films capped with aluminum. By increasing the thickness of the capping layer, we demonstrate enhanced interface sensitivity of the measurements. L2(1)-ordered CMS films show no significant temperature dependence of either the Co or Mn interface moments. However, disordered CMS films show a decreased moment at low temperature possibly caused by increased Mn-Mn antiferromagnetic coupling. It is suggested that for ordered L2(1) CMS films the temperature dependence of the tunneling magnetoresistance is not related to changes in the interface moments