Magnetodielectric effects at quantum critical fields in cobalt-containing garnets

TL;DR

This study investigates magnetodielectric effects at quantum critical points in two cobalt garnets, revealing how magnetic transitions influence dielectric properties and are linked to local chemical environments.

Contribution

The paper provides a comparative analysis of two Co2+ garnets, identifying quantum critical points through magnetocapacitance and linking magnetic behavior to crystal chemistry and density functional theory.

Findings

Field-induced transitions correspond to quantum critical points.

Magnetocapacitance measurements reveal suppression of antiferromagnetic order.

Differences in magnetic structures are due to local Co-ion environments.

Abstract

Here we present a comparative study of the magnetic and crystal chemical properties of two Co2+ containing garnets, NaCa2Co2V3O12 and CaY2Co2Ge3O12. Both phases exhibit the onset of antiferromagnetic order at 8K and 6K respectively, as well as field-induced transitions in their magnetization at 1T and around 11 T. We find these field-dependent transitions correspond to quantum critical points that result in the suppression of antiferromagnetic order and that these transitions can be clearly seen using magnetocapacitance measurements. Finally, we perform detailed crystal chemistry analyses and complimentary density functional theory calculations to show that changes in the local environment of the Co-ions are responsible for differences in the two magnetic structures and their respective properties.