Magnetic field induced quantum phase transition of the $S = 1/2$ antiferromagnet $K_2NaCrO_8$

TL;DR

This study investigates the magnetic field-induced quantum phase transition in the $S=1/2$ antiferromagnet K$_2$NaCrO$_8$, revealing critical behavior and magnetic interactions through extensive experimental techniques.

Contribution

It provides new experimental insights into the quantum phase transition and magnetic interactions in K$_2$NaCrO$_8$ under high magnetic fields.

Findings

Critical field $H_c$ = 7.270 T identified.

Quantum phase transition characterized by a critical exponent $eta$ = 0.481.

Magnetic interactions extend over intra- and inter-planar spins.

Abstract

The magnetic properties of alkali-metal peroxychromate K$_2$NaCrO$_8$ are governed by the $S = 1/2$ pentavalent chromium cation, Cr$^{5+}$. Specific heat, magnetocalorimetry, ac magnetic susceptibility, torque magnetometry, and inelastic neutron scattering data have been acquired over a wide range of temperature, down to 60 mK, and magnetic field, up to 18 T. The magnetic interactions are quasi-two-dimensional prior to long-range ordering, where $T_N = 1.66$ K in $H = 0$. In the $T \to 0$ limit, the magnetic field tuned antiferromagnetic-ferromagnetic phase transition suggests a critical field $H_c = 7.270$ T and a critical exponent $\alpha = 0.481 \pm 0.004$. The neutron data indicate the magnetic interactions may extend over intra-planar nearest-neighbors and inter-planar next-nearest-neighbor spins.