Emergence of spin-orbit order in the spinel CuCr$_2$O$_4$

TL;DR

This paper uncovers a new magnetic phase in CuCr$_2$O$_4$, revealing spin-orbit ordering and structural deformation through neutron diffraction and analysis, advancing understanding of complex magnetic phenomena.

Contribution

It reports the discovery of spin-orbit order in CuCr$_2$O$_4$ and elucidates its magnetic structure and phase transitions using neutron diffraction and symmetry analysis.

Findings

Identified a nearly collinear magnetic phase between 155 K and 125 K.

Observed development of ferrimagnetic component below 125 K.

Linked magnetic structure to spin-orbit coupling and orbital deformation.

Abstract

We determined the magnetic structure of CuCr$_2$O$_4$ using neutron diffraction and irreducible representation analysis. The measurements identified a new phase between 155 K and 125 K as nearly collinear magnetic ordering in the Cr pyrochlore lattice. Below 125 K, a Cu-Cr ferrimagnetic component develops the noncollinear order. Along with the simultaneously obtained O positions and the quantum effect of spin-orbit coupling, the magnetic structure is understood to involve spin-orbit ordering, accompanied by an appreciably deformed orbital of presumably spin-only Cu and Cr.