Thermal Expansion and Magnetostriction of LayeredCorrelated Electron Systems

Abstract

This work presents high-resolution thermal expansion and magnetostriction studies revealing magnetoelastic coupling and thermodynamic properties of single-crystals of the correlated electron systems Gd2PdSi3, Cu3Bi(SeO3)2O2Cl, and Cr2Ge2Te6. Magnetization and specific heat measurements complement the dilatometric investigations. Gd2PdSi3 is a metallic antiferromagnet with a complex phase diagram which shows three phase transitions already in zero-field. Among other magnetic orders it evolves a skyrmion lattice phase when a magnetic field is applied. This skyrmion lattice phase is strongly enhanced under the application of uniaxial pressure. New phase boundaries in the phase diagram are found and magnetoelastic coupling is quantified. The antiferromagnetic insulator Cu3Bi(SeO3)2O2Cl is a multiferroic which shows geometric frustration. Its high-temperature structural phase transition is strongly affected by uniaxial pressure, whereas pressure only has small effects on the antiferromagnetic (AFM) transition at low temperatures. The low-temperature AFM phase exhibits a metamagnetic spin-flip transition for B || c. Mixed-phase behavior and linear magnetoelastic coupling are observed in the transition region. Furthermore, the magnetic phase diagrams for the a- and b-axis of Cu3Bi(SeO3)2O2Cl are constructed for the first time. Cr2Ge2Te6 is a layered quasi-two-dimensional van der Waals material with a uniaxial magnetic anisotropy. The magnetoelastic coupling in Cr2Ge2Te6 is directly measured and correlations up to high temperature are observed. Furthermore, the critical behavior around the ferromagnetic phase transition is analyzed and a Gruneisen analysis shows that applying uniaxial pressure leads to large changes in the critical temperature.