Magnetic phase diagram of the helimagnetic spinel compound ZnCr2Se4 revisited by small-angle neutron scattering

TL;DR

This study uses small-angle neutron scattering to explore the magnetic phases of ZnCr2Se4, revealing a continuous evolution of magnetic structure, a weak jump in spiral pitch, and the absence of long-range order in the high-field phase.

Contribution

It provides detailed SANS measurements that clarify the magnetic phase diagram and the nature of phase transitions in ZnCr2Se4, especially the spin-nematic phase.

Findings

No long-range magnetic order in the high-field phase

Continuous change in magnetic structure with field and temperature

Isotropic phase transitions regardless of field direction

Abstract

We performed small-angle neutron scattering (SANS) measurements on the helimagnetic spinel compound ZnCr2Se4. The ground state of this material is a multi-domain spin-spiral phase, which undergoes domain selection in a magnetic field and reportedly exhibits a transition to a proposed spin-nematic phase at higher fields. We observed a continuous change in the magnetic structure as a function of field and temperature, as well as a weak discontinuous jump in the spiral pitch across the domain-selection transition upon increasing field. From our SANS results we have established the absence of any long-range magnetic order in the high-field (spin-nematic) phase. We also found that all the observed phase transitions are surprisingly isotropic with respect to the field direction.