Experimental and density functional theory study of the physical properties of XZnSb compounds, X = Ti, V, Cr

Abstract

We present combined experimental and density functional theory (DFT) studies on compounds XZnSb (X = Ti,V,Cr) and Ti<inf>0.5</inf>V<inf>0.5</inf>ZnSb, V<inf>0.9</inf>X<inf>0.1</inf>ZnSb (X = Ti,Cr). Physical property measurements i.e. specific heat, magnetization, electrical resistivity, Seebeck coefficient, Vickers hardness and elastic moduli were carried out for polycrystalline single-phase materials. From X-ray single crystal data and Rietveld analyses all these phases were found to crystallize with the MnAlGe-type. For all three polycrystalline compounds XZnSb (X = Ti,V,Cr) the temperature dependent electrical resistivity combines metallic (at lower) and semiconducting-like features (at higher temperatures). Low temperature specific heat data of TiZnSb and earlier studied Cr<inf>0.86</inf>ZnSb conform with a low temperature metallic behaviour, yielding electronic Sommerfeld coefficients γ = 6.4(1) mJ.mol^-1K^-2 and 10.7(5) mJ.mol^-1K^-2, respectively. The specific heat of VZnSb, however, deviates towards lowest temperatures from a simple metallic behaviour and accordingly, allowing only a rough estimate of γ, to around 6 to 8 mJ.mol^-1K^-2. While Cr<inf>0.86</inf>ZnSb exhibits antiferromagnetic order below about 200 K, magnetic susceptibility data of TiZnSb and VZnSb infer a paramagnetic behaviour. DFT calculations were made to derive various physical properties, such as structural and magnetic stabilities, charge transfer and atomic size, electronic structure (density of states, band structure), electronic transport properties (Seebeck coefficient and resistivity) within Boltzmann's transport theory, as well as elastic properties. All the results are obtained for fully relaxed structural parameters. Spin polarized DFT calculations for VZnSb result in an antiferromagnetic ground state with local V-moments of about 1 µ<inf>B</inf>, which is only slightly more stable than ferromagnetic ordering.