Field driven magnetostructural transitions in GeCo$_2$O$_4$

TL;DR

This study reveals how magnetic field application induces complex magnetostructural transitions in GeCo$_2$O$_4$, involving spin-flop and spin reorientation phenomena linked to structural symmetry changes.

Contribution

It uncovers the detailed field-driven magnetostructural transitions and the associated spin reorientations in GeCo$_2$O$_4$ using neutron and X-ray diffraction.

Findings

Magnetic field induces a spin-flop transition in GeCo$_2$O$_4$.

Structural symmetry lowers during magnetic ordering.

High magnetic fields cause a spin reorientation linked to structural changes.

Abstract

In the spinel compound GeCo$_2$O$_4$, the Co$^{2+}$ pyrochlore sublattice presents remarkable magnetic field-induced behaviors that we unveil through neutron and X-ray single-crystal diffraction. The N\'eel ordered magnetic phase is entered through a structural lowering of the cubic symmetry. In this phase, when a magnetic field is applied along a 2-fold cubic direction, a spin-flop transition of one fourth of the magnetic moments releases the magnetic frustration and triggers magnetostructural effects. At high field, these ultimately lead to an unusual spin reorientation associated to structural changes.