An inelastic neutron scattering study of the magnetic field dependence of the quantum dipolar garnet: Yb$_3$Ga$_5$O$_{12}$

TL;DR

This study uses inelastic neutron scattering to explore how magnetic field influences soft mode excitations in the quantum dipolar garnet Yb₃Ga₅O₁₂, revealing quantum nature and potential for low-temperature refrigeration.

Contribution

It provides new insights into magnetic soft modes and quantum excitations in Yb₃Ga₅O₁₂, a hyperkagome garnet with potential refrigeration applications.

Findings

Identification of robust soft modes under magnetic field

Coexistence of nanoscale magnetic structures and fluctuations

Yb₃Ga₅O₁₂ described as a quantum dipolar magnet

Abstract

The garnet compound Yb$_3$Ga$_5$O$_{12}$ is a fascinating material that is considered highly suitable for low-temperature refrigeration, via the magnetocaloric effect, in addition to enabling the exploration of quantum states with long-range dipolar interactions. It has previously been theorized that the magnetocaloric effect can be enhanced, in Yb$_3$Ga$_5$O$_{12}$ , via magnetic soft mode excitations which in the hyperkagome structure would be derived from an emergent magnetic structure formed from nanosized 10-spin loops. We study the magnetic field dependence of bands of magnetic soft mode excitations in the effective spin $S = 1/2$ hyperkagome compound Yb$_3$Ga$_5$O$_{12}$ using single crystal inelastic neutron scattering. We probe the magnetically short ranged ordered state, in which we determine magnetic nanoscale structures coexisting with a fluctuating state, and the magnetically saturated state. We determine that Yb$_3$Ga$_5$O$_{12}$ can be described as a quantum dipolar magnet with perturbative weak near-neighbor and inter-hyperkagome exchange interaction. The magnetic excitations, under the application of a magnetic field, reveal highly robust soft modes with distinctive signatures of the quantum nature of the Yb3+ spins. Our results enhance our understanding of soft modes in topological frustrated magnets that drive both the unusual physics of quantum dipolar systems and future refrigerant material design.