Abstract
The phase diagram of Mn0.957Zn0.043F2 was measured in magnetic fields H↘ up to 175 kOe, directed along the easy axis. The para‐antiferro transition, at TC(H), shows an increased roundling at finite H. At low H, the slope −dTCd(H2) is considerably larger than predicted by mean field theory. The paraspinflop boundary exhibits a much larger ’’bulge’’ than in pure MnF2. All these features are attributed to random fields. Several discrepancies from early predictions for the effects of random fields are noted, and are attributed to the absence of a genuine order‐disorder transition on the line TC (except at H = 0).