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Magnetization beyond the Ising limit of Ho2Ti2O7
Opherden, L.; Herrmannsdörfer, T.; Uhlarz, M.; Gorbunov, D. I.; Miyata, A.; Portugall, O.; Ishii, I.; Suzuki, T.; Kaneko, H.; Suzuki, H.; Wonsitza, J.;
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 ultrahigh fields up to 120 T. However, even under such extreme magnetic fields full saturation cannot be achieved. Crystal-electric-field calculations 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 new peak of the susceptibility appears around 2 T. We argue, this signals the crossover between spin-ice and polarized correlations.

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Publ.-Id: 28922 - Permalink