STUDY OF MAGNETIZATION IN MANGANITE SYSTEM IN THE PRESENCE OF LATTICE DISTORTION

Abstract

The manganites of the type Re1-xAxMnO3( Re = La , Nd , A = Ca , Sr , Ba ) are believed to be half metallic magnets exhibiting colossal magnetoresistance (CMR). The manganite system is described by a simple model Hamiltonian consisting of the hopping of the itinerant d-electrons in the doubly degenerate egband of Mn ions which is split by a static J-T lattice distortion due to band Jahn-Teller (J-T) effect. An external magnetic field results in further Zeeman splitting of the same egband. The ferromagnetism is assumed to originate from the exchange interaction between the spins of the localized core t2gelectrons. The J-T split itinerant (eg) bands are assumed to hybridize rather strongly with the on-site localized (t2g) levels. In the model under consideration the magnetization (m) as well as the lattice strain (e) are expected to depend on the model parameters of the system: i.e. the position of the localized level (d) with respect to the Fermi level, the strength of hybridization (v), the magnetic exchange coupling constant (g1), J-T coupling constant (g), external magnetic field (b) and the impurity concentration (x). The equations for the magnetization and the lattice distortion are solved self-consistently. The effect of different interactions on the quasiparticle bands and the density of states (DOS) are analyzed in detail to understand the evolution of the physical properties of the system on switching the interactions. The temperature dependence of the magnetization due to the localized electrons and that induced in the conduction band are studied.