Regensburg 2019 – wissenschaftliches Programm
MA 6.4: Vortrag
Montag, 1. April 2019, 15:45–16:00, Theater
Magnetization beyond the Ising limit of Ho2Ti2O7 — •L. Opherden1, T. Herrmannsdörfer1, M. Uhlarz1, D. I. Gorbunov1, A. Miyata2, O. Portugall2, I. Ishii3, T. Suzuki3, and J. Wosnitza1,4 — 1Hochfeld-Magnetlabor Dresden (HLD-EMFL), HZDR, Dresden, Germany — 2Laboratoire National des Champs Magnetiques Intenses (LNCMI-EMFL), Toulouse, France — 3Department of Quantum Matter, AdSM, Hiroshima University, Japan — 4Institut für Festkörper- und Materialphysik, TU Dresden, Germany
We report that the local Ising anisotropy in pyrochlore oxides – the crucial requirement for realizing the spin-ice state – can be broken by means of high magnetic fields. For the case of the well-established classical spin-ice compound Ho2Ti2O7 the magnetization exceeds the angle-dependent saturation value of the Ising limit using ultra-high fields up to 120 T. However, even under such extreme magnetic fields full saturation cannot be achieved. Crystal-electric-field calculations can account for the measured magnetization dependence and reveal that a level crossing for two of the four ion positions leads to magnetization steps at 55 and 100 T. In addition, we show that by using a field-sweep rate in the range of the spin-relaxation time, the dynamics of the spin system can be probed. Exclusively at 25 ns/T a novel peak of the susceptibility appears around 2 T. We argue, this signals the cross-over between spin-ice and polarized correlations.