Linear dichroism study of the structural phase transition of BaMnF4.

Abstract

Linear dichroism (LD) has been investigated on ferroelectric antiferromagnet BaMn${\mathrm{F}}_{4}$ in a temperature range of 15-300 K. The LD is clearly observed to reflect the order parameter of the structural phase transition (transition temperature: ${T}_{I}=252$ K) and antiferromagnetic shortrange order (N\'eel temperature: ${T}_{N}=26$ K) as in the case of linear birefringence. It is confirmed, from a jump of LD at ${T}_{I}$ and a value of critical exponent $\ensuremath{\beta}=0.23$, that a slight firstorder character is involved in the structural phase transition. No additional structural phase transition was observed below ${T}_{I}$.