Spin-flop bicritical point in MnF2

Abstract

From measurements of the susceptibility and rf absorption, we have determined the phase diagram of MnF2 near its bicritical point which is located at TB=64.792±0.001 K and HB=118.353±0.01 kOe. Alignment of easy axis and applied field was achieved within 2×10-6 rad. We find, quite accurately, an anisotropy crossover exponent φ=1.279±0.031, in good agreement with renormalization-group predictions for an n=3 component system. However, the less exactly determined amplitude ratio Q=1.56±0.35 of the two phase boundaries to the paramagnetic state, lies between that predicted for n=3 and that for n=2. The nonuniversal slope q of the t=0 scaling axis is q=(1.19±0.15)×10-6 (kOe-2) and the amplitude w+ for the spin-flop to paramagnetic phase boundary is w+=(2.67±0.3)×106 (kOe2). © 1979 The American Physical Society.