Microscopic examinations of Co valences and spin states in electron-doped LaCoO$_{3}$

TL;DR

This study investigates the valence and spin states of cobalt in electron-doped LaCoO$_{3}$ using spectroscopic techniques, revealing a low-spin Co$^{3+}$ and high-spin Co$^{2+}$ state with implications for spin blockade.

Contribution

It provides new insights into the spin states and valence configurations in electron-doped LaCoO$_{3}$, highlighting the role of covalent bonding and spin blockade phenomena.

Findings

Identification of low-spin Co$^{3+}$ and high-spin Co$^{2+}$ states at low temperatures

Confirmation of electron-hole asymmetry in electrical resistivity

Observation of a spin-blockade phenomenon in the system

Abstract

We studied the Co valences and spin states in electron-doped LaCo$_{1-y}$Te$_{y}$O$_3$ by measuring x-ray absorption spectra and electron spin resonance. The low-temperature insulating state involves the low-spin Co$^{3+}$ ($S=0$) and the high-spin Co$^{2+}$ state, which is described by $g=3.8$ and $j_{\rm eff}=1/2$. The results, in concurrence with the electron-hole asymmetry confirmed in electrical resistivity, coincide with a spin-blockade phenomenon in this system. Further, we discuss the $g$ factor in terms of the strong covalent-bonding nature and consider multiple origins of this phenomenon.