Structure, Magnetization and Resistivity of La$_{1-x}$M$_x$CoO$_3$ (M = Ca, Sr, and Ba)

TL;DR

This study explores how substituting La with different alkaline earth metals in La$_{1-x}$M$_x$CoO$_3$ affects its structure, magnetization, and resistivity, revealing non-monotonous changes influenced by ionic size and local disorder.

Contribution

It demonstrates that magnetic and transport properties depend on ionic size and local disorder, not just chemical pressure, in La$_{1-x}$M$_x$CoO$_3$ with M = Ca, Sr, Ba.

Findings

Sr doping yields higher transition temperatures and lower resistivity.

Magnetic and resistivity changes are non-monotonous with ionic size.

Local disorder significantly influences properties.

Abstract

We present an investigation of the influence of structural distortions in charge-carrier doped \lmco by substituting La$^{3+}$ with alkaline earth metals of strongly different ionic sizes, that is M = Ca$^{2+}$, Sr$^{2+}$, and Ba$^{2+}$, respectively. We find that both, the magnetic properties and the resistivity change non-monotonously as a function of the ionic size of M. Doping \lmco with M = Sr$^{2+}$ yields higher transition temperatures to the ferromagnetically ordered states and lower resistivities than doping with either Ca$^{2+}$ or Ba$^{2+}$ having a smaller or larger ionic size than Sr$^{2+}$, respectively. From this observation we conclude that the different transition temperatures and resistivities of \lmco for different M (of the same concentration $x$) do not only depend on the varying chemical pressures. The local disorder due to the different ionic sizes of La$^{3+}$ and M$^{2+}$ play an important role, too.