Magnetic and transport properties, and the phase diagram of hole-doped La1−xMgxMnO3 (x ≤ 0.4)

Abstract

A summary of detailed measurements of the field- and temperature-dependent ac susceptibility, the field-cooled and zero-field cooled magnetization, coercive field and the resistivity in zero field and applied field of 1.5 T is presented for hole-doped La1−xMgxMnO3 (0.05 ≤ x ≤ 0.4). Measurements of the ac susceptibility enable estimates of the (effective) critical exponents γ, β and δ to be made, which, when combined with the magnetization data, enable a phase diagram to be proposed. The transport data highlight the suppression of a metal–insulator transition in these systems with small average A-site radius. Furthermore, the transport behaviour is shown to be consistent with the predictions for charge transport by conventional small polaron hopping in both the paramagnetic and ferromagnetic phases, but inconsistent with recent quantitative predictions for magnetic small polaron-mediated conduction in a phase-separated picture.