Spin state transitions associated with magnetic phase separation in EuBaCo2O5+δ (δ = 0.47) cobaltite

Abstract

The EuBaCo2O5+δ (δ = 0.47) cobaltite belongs to the orthorhombic structure with the space group of Pmmm, undergoes a metal insulator transition (MIT) at 355 K and shows three different magnetic phases: one ferromagnetic phase and two antiferromagnetic phases below 300 K. The MIT is associated with a transition of the Co3+ spin state in CoO6 octahedra from the high-spin (HS) state to the intermediate spin (IS) state, and the IS state contains various magnetic phases. The Jahn teller active orbital ordered IS state is gradually transformed to low spin (LS) state, in which the magnetization progressively decreases and the resistivity increases by several orders of magnitude. The detailed analysis of magnetization, resistivity and magnetoresistance show strong correlations between the multiple magnetic phases and the spin state transitions in EuBaCo2O5+δ (δ = 0.47) cobaltite.