Xray diffraction, magnetic, and transport study of lattice instabilities and metalinsulator transition in CaV_{1x} Ti_{x} O_{3} ( 0⩽x⩽0.4 )
Abstract
CaVO_{3} is metastable in air at room temperature. Measurements below room temperature on fresh, polycrystalline CaV_{1x} Ti_{x} O_{3} , 0⩽x⩽0.4 samples that were coldpressed into dense pellets showed a resistivity ρ(T)= ρ_{0} +a T^{3/2} for x=0 and 0.05, but a ρ(T)= ρ_{0} +b T^{2} for x=0.1 and a transitional temperature dependence in x=0.2 and 0.3 to a ρ (T) ∝exp ( T_{0} /T )^{1/4} for x=0.4 . The thermoelectric power shows no phonondrag component in any sample and a systematic transition above 200 K from a small, temperatureindependent behavior in CaVO_{3} to an unusual increase with temperature in the x=0.3 and 0.4 samples. A nearly temperatureindependent paramagnetism above 150 K is enhanced relative to a conventional Pauli paramagnetism by two orders of magnitude, and the lowtemperature paramagnetism is dominated by localized spins that exhibit a sharp increase in concentration in the range 0.2<x⩽0.4 . A small step increase of the linear variation of volume with x occurs at x≈0.1 . The solidsolution range does not extend significantly beyond x=0.4 . These data are interpreted in terms of a firstorder Mott Hubbard transition manifesting itself as strongcorrelation fluctuations in a narrow π^{*} band of the VO_{3} array in CaVO_{3} and an inability to obtain complete solid solution of the CaVO_{3} CaTiO_{3} system. Substitution of Ti ( IV ) introduces Andersonlocalized states below a mobility edge μ_{c} that increases with x , crossing ∊_{F} in the range 0.2<x<0.4 . A trapping out of the strongcorrelation fluctuations as localized V(IV): t^{1} e^{0} configurations is postulated to occur for x⩾0.1 .
 Publication:

Physical Review B
 Pub Date:
 June 2004
 DOI:
 10.1103/PhysRevB.69.245118
 Bibcode:
 2004PhRvB..69x5118Z
 Keywords:

 72.80.Ga;
 71.30.+h;
 72.20.Pa;
 75.30.Cr;
 Transitionmetal compounds;
 Metalinsulator transitions and other electronic transitions;
 Thermoelectric and thermomagnetic effects;
 Saturation moments and magnetic susceptibilities