First-principles study of magnetic and spin-dependent transport properties of Mn2VZ (Z = Al, Ga) with negative spin polarization using a disordered local moment approach at finite temperatures

Abstract

First-principles studies were performed on two Mn-based ferrimagnetic Heusler compounds with L21 and B2 structures, that is, Mn2VZ (Z = Al or Ga). The aim was to investigate their magnetic properties, electronic structures, and spin-resolved longitudinal conductivity at finite temperatures. Density functional theory (DFT) and functional integral theory were used. This approach incorporates transverse spin fluctuations through a disordered local moment method and the coherent potential approximation. In all cases, the calculated theoretical Curie temperatures were lower than the experimental values. Alloys with a B2 structures exhibit higher Curie temperatures compared to compounds with an L21 structures. Calculations of the temperature dependence of the density of states (DOS) indicate that the half-metallic electronic structure collapses owing to the renormalization of transverse spin fluctuations at a finite temperatures. However, the spin-resolved longitudinal conductivities demonstrated an improved spin polarization, particularly for Mn2VGa with an L21 structure. This result contradicts predictions based on the temperature-dependent DOS. The competition between the metallic transitions, which are caused by a modification of the DOS, and scattering coming from spin-disorder explains this phenomenon. Both of these effects are induced by transverse spin fluctuations. Additionally, the results show that half-metallicity, as defined by the DOS or conductivity, is inconsistent at finite temperatures. Finally, the total energy landscape of the paramagnetic state was calculated using the fixed spin moment method to investigate the strength of the longitudinal spin fluctuations. These results suggest that the alloys may exhibit strong longitudinal spin fluctuations.

arXiv comment11 pages, 5 figures

References in corpus (22)

• Slater-Pauling Behavior of the Half-Ferromagnetic Full-Heusler Alloys
• Introduction to half-metallic Heusler alloys: Electronic Structure and Magnetic Properties
• Realization of spin gapless semiconductors: the Heusler compound Mn2CoAl
• First-principles calculation of the intersublattice exchange interactions and Curie temperatures of full Heusler alloys Ni2MnX (X=Ga, In, Sn, Sb)
• Half-Metallic Ferrimagnetism in Mn_2VAl
• Temperature dependent magnetic anisotropy in metallic magnets from an ab-initio electronic structure theory: L1_0-ordered FePt
• Search for half-metallic ferrimagnetism in V-based Heusler alloys Mn${}_2$VZ (Z$=$Al, Ga, In, Si, Ge, Sn)
• Guidelines for understanding cubic manganese-rich Heusler compounds
• Calculating linear response functions for finite temperatures on the basis of the alloy analogy model
• Thermal collapse of spin-polarization in half-metallic ferromagnets
• Non-quasiparticle states in Co${}_2$MnSi evidenced through magnetic tunnel junction spectroscopy measurements
• Completely compensated ferrimagnetism and sublattice spin crossing in the half-metallic Heusler compound Mn1.5FeV0.5Al
• Electron Correlations and the Minority-Spin Band Gap in Half-Metallic Heusler Alloys
• Prediction of the Curie temperature considering the dependence of the phonon free energy on magnetic states
• Electronic Structure and Magnetic Properties of Half-metallic Ferrimagnet Mn${}_2$VAl Probed by Soft X-ray Spectroscopies
• First principles studies of the Gilbert damping and exchange interactions for half-metallic Heuslers alloys
• Majority-spin non-quasiparticle states in half-metallic ferrimagnet Mn${}_2$VAl
• Half-metallicity of Mn2VAl ferrimagnet revealed by resonant inelastic soft x-ray scattering under magnetic field
• Exchange coupling constants at finite temperature
• Finite-temperature second-order perturbation analysis of magnetocrystalline anisotropy energy of L10-type ordered alloys
• Magnetization and exchange-stiffness constants of Fe-Al-Si alloys at finite-temperatures: A first-principles study
• First-principles study of exchange stiffness constant of half-metallic Heusler alloys Co2MnZ (Z= Si, Al) at finite temperatures: Spin fluctuation-induced effective half metallicity