Dresden 2020 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 6: Cooperative Phenomena and Phase Transitions (joint session MA/TT)

TT 6.2: Vortrag

Montag, 16. März 2020, 09:45–10:00, HSZ 401

Lattice effects in pyrochlore compounds A2B2O7 — •M. Doerr1, T. Stoeter1,2, S. Granovsky1, S. Zherlitsyn2, and J. Wosnitza1,21Institut für Festkörper- und Materialphysik, TU Dresden — 2Hochfeld-Magnetlabor Dresden, Helmholtz-Zentrum Dresden-Rossendorf

The magnetic character of pyrochlores A2B2O7 (A = rare earths, B = transition metals or p-elements, e.g. Ti, Zr, Hf, Sn) strongly depends on the lattice. The ionic radii determine their existence and stability. The question of whether the ground state is degenerated or magnetically ordered is decisively determined by the ratio of dipole and exchange interaction. We present investigations of thermal expansion, magnetostriction and relaxation processes at temperatures down to 0.05 K. Dy2Ti2O7 and Ho2Ti2O7 show a number of anomalies that can be explained with both exchange and crystal-field effects. These anomalies reflect as well the magnetic properties via magnetoelastic coupling. Thus, statements on the monopole dynamics can be derived from relaxation processes. Relaxation times in the order of 103 s evidence the formation and annihilation of monopoles in the kagome-ice and saturated phase, in accordance with the known magnetic phase diagram. In contrast, the lattice effects in Dy2Sn2O7 and Ho2Sn2O7 are rather negligible. At last, measurements on Pr2Zr2O7, Gd2Zr2O7 and Nd2Hf2O7 allow the direct comparison of classical spin-ice compounds to pyrochlores with light rare earths. A representation-theoretic investigation of the symmetry group of the pyrochlore lattice could lead to a better understanding of the magnetoelastic coupling mechanisms.

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