arXiv subjects

W. Schranz

Publications and source records attributed to W. Schranz.

21 records · Page 2Linked to original sources

arXiv2010

Critical behaviour of the thermal properties of KMnF3

An ac photopyroelectric calorimeter has been used to simultaneously measure the specific heat, thermal conductivity, and thermal diffusivity around the antiferromagnetic to paramagnetic phase transition in KMnF3. It has been found that the critical exponent and the amplitude ratio of the thermal diffusivity are the same as those of the specific heat. Both values agree with the predictions of the three-dimensional Heisenberg model for isotropic magnets, although this transition is not only magnetic but also structural as well. The thermal conductivity shows a broad peak at the Neel temperature that could be related to a reduction of the phonon scattering by the spin fluctuation as the transition temperature is approached.

cond-mat.mtrl-sci↗

arXiv2010

Finite strain Landau theory of high pressure phase transformations

The properties of materials near structural phase transitions are often successfully described in the framework of Landau theory. While the focus is usually on phase transitions, which are induced by temperature changes approaching a critical temperature T-c, here we will discuss structural phase transformations driven by high hydrostatic pressure, as they are of major importance for understanding processes in the interior of the earth. Since at very high pressures the deformations of a material are generally very large, one needs to apply a fully nonlinear description taking physical as well as geometrical nonlinearities (finite strains) into account. In particular it is necessary to retune conventional Landau theory to describe such phase transitions. In Troster et al (2002 Phys. Rev. Lett. 88 55503) we constructed a Landau-type free energy based on an order parameter part, an order parameter-(finite) strain coupling and a nonlinear elastic term. This model provides an excellent and efficient framework for the systematic study of phase transformations for a wide range of materials up to ultrahigh pressures.

cond-mat.mtrl-sci↗

arXiv2005

On Static Dielectric Response of Microcomposites of the Type: Ferroelastics - Dielectrics

We describe the static dielectric response of ferroelastic-dielectric microcomposites. Its dependence on temperature, pressure and concentration is considered for smaller concentrations and for temperatures above the critical temperature. We have found a qualitative agreement with existing experimental data for $Al_{2}(WO_{4})_{3}$.

cond-mat.mtrl-sci↗