Optical Measurement of the Magnetic Tricritical Behavior of FeCl2

Abstract

The magnetic tricritical behavior of Fe${\mathrm{Cl}}_2$ has been measured using an optical technique in which magnetic circular dichroism is used to determine the total magnetization as a function of temperature and magnetic field. We report tricritical point exponents ${\beta }_u$, ${\beta }_{+}$, and ${\beta }_{-}$ that are consistent with Landau theory, and a magnetization versus temperature phase diagram that exhibits a discontinuity in slope between the $M^{+}$ and $M_{\lambda }$ branches at the tricritical point.