Effect of iron-doping on spin-state transition and ferromagnetism in Pr$_{0.5}$Ca$_{0.5}$CoO$_{3-\delta}$ cobalt oxides

TL;DR

This study investigates how iron doping affects the spin-state transition and ferromagnetism in Pr$_{0.5}$Ca$_{0.5}$CoO$_{3-elta}$ cobalt oxides, revealing that Fe doping suppresses spin-state transitions and influences magnetic properties.

Contribution

It provides new insights into the effects of iron doping and annealing conditions on spin-state transitions and ferromagnetism in cobalt oxides, highlighting the role of cell volume and Fe-O bonds.

Findings

Iron doping suppresses spin-state transitions.

Annealing under high oxygen pressure enhances spin-state transition in iron-free samples.

Fe doping maintains ferromagnetic transition temperature regardless of annealing conditions.

Abstract

Resistivity and dc magnetization measurements were performed for the polycrystalline Pr$_{0.5}$Ca$_{0.5}$Co$_{1-x}$Fe$_{x}$O$_{3-\delta}$ ($x$ = 0, 0.05, 0.10 and 0.15) samples. The as-fabricated samples exhibit ferromagnetic (FM) transition and the transition temperature increases with increasing the iron doping level. Annealing under high oxygen pressure induces a spin-state transition of Co ions in the \emph{iron-free} sample and such transition is reinforced with increasing the annealing oxygen pressure, while the annealing under high oxygen pressure suppresses the ferromagnetic ordering. Contrary to the case of the \emph{iron-free} sample, no spin-state transition is induced by the annealing under high oxygen pressure for the \emph{iron-doped} samples, and the ferromagnetic transition temperature is nearly independent of the annealing procedures. The enhancement of the spin-state transition in the \emph{iron-free} sample after annealing under high oxygen pressure should be attributed to the reduction of the cell volume. The suppression of the spin-state transition by the Fe doping is related to the enlargement of the cell volume and the stronger Fe-O bonds than Co-O bonds. The enhancement of the ferromagnetism by the iron-doping might arise from the ferromagnetic exchange interaction between Fe$^{3+}$ and Co$^{4+}$ through oxygen (Fe$^{3+}$-O-Co$^{4+}$).