4th internal biannual science meeting of the MLZ

Temperature dependence of the crystal structure and magnetic properties of MnFe4Si3 at high pressures

27 Jun 2019, 09:40

20m

Library

Short talk Science group meetings 2

Speaker

Mr Andreas Eich ((1) Institute of Crystallography, RWTH Aachen University; (2) Jülich Centre for Neutron Science-2/Peter Grünberg Insitute-4, Forschungszentrum Jülich GmbH)

Description

Refrigeration based on the magnetocaloric effect is a potential alternative to conventional vapor compression refrigeration. One system of particular interest with regard to application is Mn${}_{5-\mathit{\text{x}}}$Fe${}_{\mathit{\text{x}}}$Si${}_3$ [1-3]. Pressure affects the interatomic distances in the crystal structure and thus has an influence on the magnetic properties.

The aim of this work is to establish the influence of hydrostatic pressure on the crystal structure of MnFe${}_4$Si${}_3$ as well as the pressure dependence of the magnetic transition of MnFe${}_4$Si${}_3$, which at ambient pressure orders ferromagnetically at ${\mathit{\text{T}}}_C$ ≈ 300 K. Synchrotron X-ray powder diffraction measurements were carried out up to 12.5 GPa between 100 K and 373 K. Isofield magnetization measurements and neutron single-crystal diffraction were used to determine the magnetic transition temperature up to pressures of 1 GPa.

MnFe${}_4$Si${}_3$ shows no clear indication of phase transitions at high temperatures (296 K–373 K) and high pressures. At low temperatures (200 K, 250 K), anomalies in the lattice parameters occur as a function of pressure. They might be related to a transition into a magnetically ordered phase. The trend of decreasing magnetic transition temperature with increasing pressure is also observed in magnetization data and in the intensities of selected magnetic reflections from neutron diffraction experiments at 1 GPa. The pressure-dependent unit cell volume data at 100 K and 150 K exhibit anomalies as two equations of state are necessary to fit each of the data sets, respectively.

[1] Bińczycka et al. Phys. Stat. Sol. 1973 19, K13-K17
[2] Hering et al. Chem. Mater. 2015 27, 7218-7136
[3] Song et al. J. Alloys Compd. 2002 334, 249-252