Low-Temperature Adiabatic Studies of Spin-Flop States in Antiferromagnets

The theoretical basis for adiabatic investigations of antiferromagnetic spin-flop states is given. Experimental details of such experiments are briefly described and results of such experiments on Co${\mathrm{Cl}}_2$·6${\mathrm{H}}_2$O and Mn${\mathrm{Cl}}_2$·4${\mathrm{H}}_2$O, which have known spin-flop states, are given. Results are also presented indicating that the two antiferromagnetic substances Co${\mathrm{Br}}_2$·6${\mathrm{H}}_2$O and Fe${\mathrm{Cl}}_2$·4${\mathrm{H}}_2$O exhibit spin flopping in accessible experimental regions. Co${\mathrm{Br}}_2$·6${\mathrm{H}}_2$O has a critical field of the order of 7500 G in the region 1.15°K to its triple point, 2.91°K. Fe${\mathrm{Cl}}_2$·4${\mathrm{H}}_2$O apparently exhibits spin flop below 0.68°K above a field equal to about 5500 G. The method also shows the lack of spin flopping in Mn${\mathrm{Br}}_2$·4${\mathrm{H}}_2$O below 10 000 G above 1°K.