A Neutron Scattering Study of the H-T Phase Diagram of the Bond Frustrated ZnCr2S4

TL;DR

This neutron scattering study maps the complex magnetic phase diagram of ZnCr2S4, revealing field-dependent magnetic transitions and spin wave behaviors linked to structural instabilities and Jahn-Teller effects.

Contribution

It provides detailed experimental insights into the magnetic phases and excitations of ZnCr2S4, highlighting the interplay between magnetic order, structural changes, and external magnetic fields.

Findings

Identification of two antiferromagnetic transitions at 15.5 K and 8 K.

Observation of a spin wave gap opening below 8 K.

Magnetic field closes the spin wave gap.

Abstract

Detailed neutron scattering measurements on the bond frustrated magnet ZnCr2S4 reveal a rich H-T phase diagram. The field dependence of the two subsequent antiferromagnetic transitions follows closely that of recently reported structural instabilities, providing further evidence for spin driven Jahn-Teller physics. The incommensurate helical ordered phase below TN1 = 15.5 K exhibits gapless spin wave excitations, whereas a spin wave gap (about 2 meV) opens below TN2 = 8 K as the system undergoes a first-order transition to a commensurate collinear ordered phase. The spin wave gap is closed by a strong magnetic field.