The structural phase transition in SrTiO3 under uniaxial stress in the [110] direction: A calorimetric study

The excess specific heat of the structural phase transition of SrTiO3 has been measured on single crystals under uniaxial stress along the crystallographic [110] direction and for extremely slow cooling rates. The corresponding excess entropy scales as the square of the thermodynamic order parameter. The order parameter exponent is beta = 0.35 +/- 0.02 for stress-free samples and increases systematically with increasing stress. At a stress of 5 bar the exponent is beta = 0.5 and the phase transition follows mean-field behaviour.