EG-14 Theoretical and experimental investigation of half-metallic properties in V2CoAl

We present results of a combined experimental and computational investigation of electronic, magnetic, and structural properties of V2CoAl, a Heusler compound exhibiting nearly half-metallic electronic structure at equilibrium. Our calculations indicate that this alloy crystallizes in inverted Heusler cubic structure. The magnetic alignment of this material is ferrimagnetic, due to the anti-aligned magnetic moment of two vanadium sub-lattices. V2CoAl retains its nearly perfect spin polarization under compression of the unit cell volume. At the same time, the spin polarization is strongly reduced under expansion of the unit cell volume. The reduction of the spin polarization at larger lattice constants is due to the rigid shift of the spin-up states, which results in modified exchange splitting. Although the perfectly ordered cubic structure is assumed in the theoretical calculations, the bulk sample prepared using arc melting and annealing crystallizes in the disordered cubic structure. With proper annealing conditions (700 °C for 1 week), samples with B2 type disorder have been obtained. The disordered sample shows ferrimagnetic order with a Curie temperature of about 80 K (see Fig. 1), and high-field (H = 9 T) magnetization at 2K of 0.6 emu/g. In this presentation, we will also discuss the computational results on the effect of disorder and the electrical transport properties measured on the disordered samples. This research is supported by the National Science Foundation (NSF) under Grant Numbers 2003828 and 2003856 via DMR and EPSCoR. Mohd Anas is supported by DOE EPSCoR (DE-SC0024284) grant.