On the Mechanism of the Spin State Transition of (Pr1-ySmy)1-xCaxCoO3

TL;DR

This study investigates the spin state transition in (Pr1-ySmy)1-xCaxCoO3, revealing a structural phase change from intermediate to low spin states with temperature, and constructing phase diagrams to understand the effects of composition.

Contribution

It provides new phase diagrams and insights into the spin state transitions influenced by chemical composition and temperature in (Pr1-ySmy)1-xCaxCoO3.

Findings

Structural phase transition from IS to LS state with decreasing temperature.

Decreasing nIS with increasing y or decreasing x.

Transition becomes a gradual crossover with composition changes.

Abstract

Transport, thermal and magnetic measurements have been carried out on (Pr1-ySmy)1-xCaxCoO3. The system exhibits a structural phase transition accompanied by the spin state change from the intermediate spin (IS) state to the low spin (LS) state with decreasing temperature T. We have constructed a T-y phase diagram for x=0.3 and T-x ones for y=0.2 and 0.3. By analyzing their magnetic susceptibilities, the number of Co ions excited to IS state (or the electron number in the eg orbitals), nIS, are roughly estimated. With increasing y or with decreasing x, nIS decreases, and the phase transition changes gradually to the (IS-LS) crossover-like one. We discuss on the possible role of the Pr atoms in realizing the transition.