Effect of Ga and Ge substitution in the Mn site of rare earth manganates on charge ordering and related properties

Abstract

The effect of substitution of Ga and Ge in the Mn site on the magnetic and electrical transport properties of three charge-ordered rare-earth manganates, Nd 0.5Ca 0.5MnO 3, Nd 0.5Sr 0.5MnO 3 and Ca 0.64Pr 0.36MnO 3 has been investigated. Substitution by Ga and Ge affects the properties of these charge-ordered manganates differently though they both have the d 10 electron configuration. Thus, Ga doping in Nd 0.5Ca 0.5MnO 3 is more effective in destroying the charge ordering than Ge doping, the latter requiring higher concentrations. Substitution of Ga in Nd 0.5Sr 0.5MnO 3 destroys ferromagnetism whereas Ge substitution does not. The charge-ordered antiferromagnetic transition is destroyed by both Ga and Ge substitution and the Ge substituted compositions show itinerant electron behavior while the Ga substituted compositions become insulators. Both Ga and Ge substitution have negligible effect on the charge-ordered state of Ca 0.64Pr 0.36MnO 3.