Tetracritical points in antiferromagnetic systems

Abstract

It is pointed out that certain $\mathrm{XY}$-like antiferromagnets, including ${\mathrm{Cr}}_2$Te${\mathrm{O}}_6$ and KCu${\mathrm{F}}_3$, should exhibit a tetracritical point at ($T=T_N$, $\overrightarrow{H}=0\mathrm{}$) when the magnetic field $\overrightarrow{H}$ is applied along a symmetry axis. The zero-temperature critical field is estimated to be of order 1 kG. The predictions of scaling and renormalization-group theories for tetracritical points may be tested experimentally on these antiferromagnets.