Relaxation Phenomena of Metamagnetic Transition in CoCl2·2H2O

The relaxation phenomena associated with the metamagnetic phase transition in CoCl 2 ·2H 2 O, have been studied by applying the A. C. susceptibility measurement method under high external magnetic field up to 54 kOe parallel to the easy direction. (i) from the frequency dependence of height of peaks of A. C. susceptibility, χ' and χ'', at transition points, the relaxation time τ's is estimated. τ(at H c 1 =31.6 KOe)>2×10 -3 sec, and τ (at H c 2 =46.0 kOe)\( 2{×}10⁻⁵\) sec at 4.2 K. Both tend longer as temperature as temperature goes down from 4.2 to 1.6 K. (ii) there are two another susceptibility peaks at 36.8 ond 41.1 kOe besides those at H c 1 and H c 2 . (iii) height of these peaks showed hysteresis on the sweep direction. (iv) a step in magnetization curve is found 36.8 kOe in addition to the steps at H c 1 and H c 2 . A tentative explanation is given of these phenomena from the view point of metastable domain.