Magnetic frustration in the spinel compounds Ge Co_2 O_4 and Ge Ni_2 O_4

TL;DR

This study investigates magnetic frustration in GeCo₂O₄ and GeNi₂O₄ spinel compounds, revealing similar magnetic ground states despite differing exchange interactions and frustration criteria, through neutron diffraction and high-field magnetization.

Contribution

It provides a detailed analysis of magnetic exchange interactions and frustration mechanisms in GeCo₂O₄ and GeNi₂O₄, highlighting their similar magnetic behavior despite different anisotropies.

Findings

Similar magnetic ground states at low temperature.

Different energy scales for magnetic behavior.

Frustration mechanisms explained by exchange interactions.

Abstract

In both spinel compounds GeCo$_2$O$_4$ and GeNi$_2$O$_4$ which order antiferromagnetically (at $T_N = 23.5 K$ and $T_{N_1} = 12.13 K$, $T_{N_2} = 11.46 K$) with different Curie Weiss temperatures ($T_{CW}$=80.5 K and -15 K), the usual magnetic frustration criterion $f=|T_{CW}|/T_N>>1$ is not fulfilled. Using neutron powder diffraction and magnetization measurements up to 55 T, both compounds are found with a close magnetic ground state at low temperature and a similar magnetic behavior (but with a different energy scale), even though spin anisotropy and first neighbor exchange interactions are quite different. This magnetic behavior can be understood when considering the main four magnetic exchange interactions. Frustration mechanisms are then enlightened.