Dimer breaking and high-temperature ferromagnetism inLaCo2(Ge1−xPx)2

Abstract

We report the destabilization of the lattice collapsed phase of ${\text{LaCo}}_2{\text{Ge}}_2$ due to $X\text{−}X$ $\left(X={\text{Ge}}_{1-x}{\text{P}}_x\right)$ dimer breaking in the ${\text{LaCo}}_2{\left({\text{Ge}}_{1-x}{\text{P}}_x\right)}_2$ solid solution. The magnetic properties of the system are strongly affected. P substitution for Ge can first be understood as a simple band-filling effect that drives the system from a Pauli paramagnet to a ferromagnet for $0\le x\le 0.7$. The ferromagnetic Curie temperature $\left(T_{\text{C}}\right)$ reaches 230 K for $x=0.7$. For $0.7\le x\le 1$, however, the extra electron donated by the P substitution is consumed in breaking the $X\text{−}X$ dimers present, decreasing the layer-to-layer magnetic coupling and correspondingly suppressing $T_{\text{C}}$.