LONG-TIME DECAY OF THERMOREMANENT MAGNETIZATION THROUGH STEPWISE CHANGES OF THE REENTRANT SPIN-GLASS-LIKE STATE IN THE NI2IN-TYPE MN7SN4

The zero-field-cooled magnetization at the magnetic field H = 300 Oe s hows anomolous kinks at T-A and T-B(> TA) far below the reentrant spin -glass-like transition temperature T-f (above which a long-range ferri magnetic ordering is set up). The irreversibility between the zero-fie ld-cooled and the field-cooled magnetizations, and the time decay of t he thermoremanent magnetization (sigma(TRM)) are observed below the fe rrimagnetic Curie temperature Tc. The decay feature can be described b y Ogielski's power law sigma(TRM) = At-a whose a exhibits peaks at T-A T-B, T-f, and T-C The peak of a at Te can be fitted by the combinatio n of Ising type and Ginzburg-Landau type expressions. Three stepwise c hanges of the spin-glass-like state below T-f and the feature of the c oexistence of short-range spin-glass and long-range magnetic ordering components above T-f are discussed.