Phase Diagram of a Quasi-One-Dimensional Antiferromagnet (CH₃)₄NMnCl₃(TMMC)

Abstract

The magnetic phase diagram of the most typical quasi-one-dimensional antiferromagnet (CH₃)₄NMnCl₃(T_N=0.835 K) has been established. An anisotropic axis has been found in the hexagonal plane perpendicular to c-axis. When the magnetic field H is applied along the easy axis in the plane, the Néel temperature T_N(H) shifts down to the bicritical point at (T_b=0.5 K, H_b=11.4 kG) on the (T-H) diagram, and for H>H_b, T_N(H) turns to increase monotonously. T_N(H) for the hard axis shows an anomalous increase as has been reported experimentally and theoretically for quasi-one-dimensional antiferromagnets.