The Magnetic Aftereffect in the Triangular XY-Like Antiferromagnet RbFeCl3

The triangular XY-like antiferromagnet RbFeCl 3 shows successive incommensurate-incommensurate-commensurate phase transitions with decreasing temperature in zero field. The T - H phase diagram in the easy plane is determined by the susceptibility measurement. Two new ordered states are found in the magnetic field region between 5 and 22 kOe. Magnetic aftereffects are observed in the commensurate phase at the lowest temperatures in zero field. The susceptibility just after the demagnetization is larger than that before the field application and decreases with a logarithmic time decay.