Regensburg 2019 – wissenschaftliches Programm
MA 6.11: Vortrag
Montag, 1. April 2019, 17:45–18:00, Theater
Frustrated Ising magnetism of TmMgGaO4 — Yuesheng Li, •Alexander A. Tsirlin, and Philipp Gegenwart — EP VI, EKM, University of Augsburg, Germany
Motivated by the interesting spin-liquid physics of the triangular antiferromagnet YbMgGaO4, we studied its Tm-based analog. Unlike Yb3+, Tm3+ is a non-Kramers ion that would normally feature non-magnetic singlet as the crystal-field ground state. However, random crystal electric field (CEF) caused by the random distribution of Mg and Ga in the structure mixes two lowest-lying CEF singlets into a quasidoublet that gives rise to Ising-like pseudospins with g||≃ 13.2 and g⊥≃ 0. Low-temperature thermodynamic measurements indicate three field-induced phase transitions that can be broadly understood within the J1zz−J2zz Ising model on the triangular lattice, albeit with a distribution of the critical fields and underlying exchange couplings. Interestingly, only one ordered state, the 1/3-plateau below 2.5 T, shows long-range order confirmed by neutron diffraction, whereas other ordered states expected in the J1zz−J2zz triangular Ising antiferromagnet seem to be only short-range in nature. Moreover, no zero-point entropy is observed.