Investigation on Microscopic Dynamics of Metamagnetic Transition in COCl₂·2H₂O

Abstract

The microscopic dynamics of the metamagnetic transition of CoCl₂·2H₂O was investigated by the measurements of the magnetization process at a constant temperature as a function of time, and the field points of temperature spikes (ΔT) in the course of adiabatic magnetization. The time required for the AF–FI transition, τ_AF–FI, was measured by the field-step method. τ_AF–FI (T, H)=4.0×10⁻⁸·exp(9.0×10⁻³|H−H^*|⁄T) sec, where H^* was 39 kOe in H_inc and 24 kOe in H_dec. The series of delayed AF–FI transition points predicted by Tinkham were detected by measuring the ΔT spikes and magnetization steps at 1.4≤T≤4.2 K. ΔT spikes were found at some other points (<H_C2) which corresponded to the rearrangement of the mis-fitting spin-sites. From the various anomalies of hysteresis phenomena, which were newly found comparing the results in the field returned back before and after passing H_C2, the mechanism of the rearrangement could be discussed.