Magnetic-Phase Diagram of MnF2from Ultrasonic and Differential Magnetization Measurements

The magnetic-phase diagram, in the $H-T$ plane, of Mn${\mathrm{F}}_2$ was measured using ultrasonic and differential magnetization techniques. The paramagnetic-antiferromagnetic boundary, for $\overrightarrow{\mathrm{H}}$ along the $c$ axis, is well represented by $T_{\mathrm{N}}-T=(1.65\mathrm{}\pm 0.15)\times {10}^{-10\mathrm{}}{H}^2$ °K/${\mathrm{G}}^2$. The triple point is at $T_3=65.1\mathrm{}\pm 0.2°$K and $H_3=120\mathrm{}\pm 4$ kG. The phase boundaries are discussed in light of existing theories.