Birefringence Study of the Criticality of the Magnetic Phase Transition in RbNiCl_3

概要

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Short-range spin ordering of RbNiCl. in the critical region of the magnetic phasetransition is observed by the birefringence technique. The temperature derivative ofthe *c-plane birefringence, corresponding to specific heat, shows an almost divergentanomaly at 11.3 K, which is resulted from coalescing two singularities at the successive phase transitions inherent to an Ising-like Heisenberg triangular lattice antifer-romagnet. The critical exponent fi is determined as 0.76:0.03 from the data on thetemperature dependence of the symmetry-breaking birefringence ,l n". The almostdivergent anomaly of specific heat and the value of p mean that the criticality does notbelong to the 3d-,X' Y universality class, in which a cusp-like anomaly in specific heatand p of 0.85, are theoretically predicted for both of the successive phase transitionsof Ising-like Heisenberg triangular lattice antiferromagnets. This can be explained bythe crossover effect from the universality class of 3d-SO(3) or 3d-S. X S. to the 3d-X Y,as concluded in a recent neutron scattering study.Imagnetic phase transition, critical phenomena, triangular lattice antifer- ll romagnet, RbNiCl3, birefringencel
社団法人日本物理学会の論文
1991-12-15