| Abstract: | Temperature and pressure derivatives of the elastic constants, indices of refraction, dielectric constants, Faraday effect and thermal expansion of RbMnCl3 near Tc = 278 K confirm the existence of a second-order phase transition. A strongly anomalous behaviour is observed with the elastic shear stiffness c44 which possesses a positive temperature derivative and a negative pressure derivative. These properties and also the pressure derivative of the transition temperature, dTc/dp = 6.2 K kbar−1 closely resemble the anomalous behaviour of two other ferroelectric species, betaine borate and betaine hydrogen maleinate. |
