Magnetic Phase Transition of Antiferromagnet with Weak Canting Interaction

Abstract

The magnetic critical phenomena of canted antiferromagnet in two dimensional lattice; Mn(HCOO)₂·2H₂O were studied by the measurement of the dependences of AC magnetic susceptibility on amplitude and frequency of measuring AC field. The induced uniform susceptibility χ_i^u in the immediate neighborhood of T_N could be successfully derived by analyzing the results. The critical divergence of χ_i^u at T_N found to be well expressed as |T−T_N|^−γ and γ=1.7±0.1. The value of γ is discussed in the view point of magnetic ordering in two dimensional lattice. The magnetic dispersion of χ_i^u was observed in very low frequency region. It is probably the first observation of critical dispersion of magnetic susceptibility near T_N. The result is discussed from the phenomenological point of view for canted antiferromagnet and it is suggested that it directly reflects the critical slowing down of antiferromagnetic staggered mode through weak canting interaction of this salt.