Magnetic Transition on Cooling Course for Some Ferromagnetic, Ferrimagnetic and Antiferromagnetic Materials

Abstract

Differential thermal analyses (DTA) by heating and cooling are carried out for some ferromagnetic (Fe-5 at%Cr), ferrimagnetic (Fe₃O₄, NiFe₂O₄, Li_0.5Fe_2.5O₄, BaO·6Fe₂O₃, SrO·5.6Fe₂O₃) and antiferromagnetic (NiO) materials respectively. Though each specimen has a sharp λ-type peak at the magnetic transition point T_C or T_N on the heating DTA curve, a λ-type peak with a rounded top is observed for each specimen at temperatures a little below the transition point on cooling. It can be interpreted that the nucleation and growth of the magnetic domain in a non-magnetic matrix starts from T_C or T_N on cooling.