First-principles study of spin-dependent thermoelectric properties of half-metallic Heusler thin films between platinum leads

Abstract

The electronic and magnetic bulk properties of half-metallic Heusler alloys such as Co 2 FeSi, Co 2 FeAl, Co 2 MnSi, and Co 2 MnAl are investigated by means of ab initio calculations in combination with Monte Carlo simulations. The electronic structure is analyzed using the plane-wave code QUANTUM ESPRESSO and the magnetic exchange interactions are determined using the Korringa-Kohn-Rostoker (KKR) method. From the magnetic exchange interactions, the Curie temperature is obtained via Monte Carlo simulations. In addition, electronic transport properties of trilayer systems consisting of two semi-infinite platinum leads and a Heusler layer in-between are obtained from the fully relativistic screened KKR method by employing the Kubo-Greenwood formalism. The focus is on thermoelectric properties, namely, the Seebeck effect and its spin dependence. It turns out that already thin Heusler layers provide highly spin-polarized currents. This is attributed to the recovery of half-metallicity with increasing layer thickness. The absence of electronic states of spin-down electrons around the Fermi level suppresses the contribution of this spin channel to the total conductance, which strongly influences the thermoelectric properties and results in a spin polarization of thermoelectric currents.

Half-metallicity and magnetism in the Co2MnAl/CoMnVAl heterostructure

“…In bulk Co 2 MnAl, the J ij 's decay quite fast with the interatomic distance and therefore the dominant coupling is the nearest-neighbour ferromagnetic interaction between Co and Mn atoms. The present feature is in good agreement with prior DFT studies [68] and is in- dependent of the method used for treating correlation effects. Consistently with the PDOS (Fig.…”

First-principles studies of the Gilbert damping and exchange interactions for half-metallic Heuslers alloys

“…Using the ASA, the T c of both the Co 2 MnZ and Co 2 FeZ systems is consistently underestimated with respect to experimental results, as shown in Table IV. The same underestimation has been observed in previous theoretical studies 78 , for systems such as Co 2 Fe(Al,Si) and Co 2 Mn(Al,Si). However, using a full potential scheme instead leads to Curie temperatures in better agreement with the experimental values, specially when the exchange correlation potential is considered to be given by the GGA (see Table IV).…”

Improvement of the Half-Metallic Stability of Co₂FeAl Heusler Alloys by GeTe-Doping

“…Content may change prior to final publication. [15], [18]. The nearly integer spin magnetic moment of Co2FeAl is compatible with the Slater-Pauling rule (m = (Nv − 24)µB , where Nv is the number of valence electrons in the primitive cell containing four atoms [19]).…”