Metallic and semi-conducting resistivity behaviour of La0.7Ca0.3−xKxMnO3 (x = 0.05, 0.1) manganites

محورهای موضوعی : Journal of Theoretical and Applied Physics

Dinesh Varshney ¹ , Neha Dodiya ²

1 - Materials Science Laboratory, School of Physics, Vigyan Bhawan, Devi Ahilya University
2 - Materials Science Laboratory, School of Physics, Vigyan Bhawan, Devi Ahilya University

تاریخ انتشار : 1393/12/10

کلید واژه: Magnetic materials, Ab initio calculations, Electrical properties, Phonons,

چکیده مقاله :

AbstractThe temperature dependence of electrical resistivity, ρ, of ceramic La0.7Ca0.3−xKxMnO3 (x = 0.05, 0.1) is investigated in metallic and semi-conducting phase. The metallic resistivity is attributed to be caused by electron–phonon, electron–electron and electron–magnon scattering. Substitutions affect average mass and ionic radii of A–site resulting in an increase in Debye temperature θD attributed to hardening of lattice with K doping. The optical phonon modes shift gradually to lower mode frequencies leading to phonon softening. Estimated resistivity compared with reported metallic resistivity, accordingly ρdiff. = [ρexp. − {ρ0 + ρe−ph (=ρac + ρop)}], infers electron–electron and electron–magnon dependence over most of the temperature range. Semi-conducting nature is discussed with variable range hopping and small polaron conduction model. The decrease in activation energies and increase in density of states at the Fermi level with enhanced Ca doping is consistently explained by cationic disorder and Mn valence.