Unconventional magnets in external magnetic fields

TL;DR

This review discusses how external magnetic fields influence frustrated magnetic systems in two or more dimensions, highlighting phenomena like magnetocaloric effects, magnetisation plateaux, and lattice geometry tuning.

Contribution

It provides a comprehensive overview of phenomena in frustrated magnets under magnetic fields, emphasizing the interplay of field, entropy, and lattice geometry, with insights into unusual excitations and dimensional reduction.

Findings

Magnetocaloric properties show field-tuned degeneracies.

Magnetisation plateaux reveal fluctuation physics and excitations.

Lattice geometry can be tuned by magnetic fields, enabling dimensional control.

Abstract

This short review surveys phenomena observed when a magnetic field is applied to a system of localised spins on a lattice. Its focus is on frustrated magnets in dimension $d \geq 2$. The interplay of field and entropy is illustrated in the context of their unusual magnetocaloric properties, where field-tuned degeneracies assert themselves. Magnetisation plateaux can reveal the physics of fluctuations, with unusual excitations (such as local modes, extended string defects or monopoles) involved in plateau termination. Field-tuning lattice geometry is the final topic, where mechanisms for dimensional reduction and conversion between different lattice types are discussed.