Low-temperature high-frequency dynamic magnetic susceptibility of classical spin-ice Dy$_2$Ti$_2$O$_7$

Abstract

MHz) AC magnetic susceptibility, χ AC , of Dy 2 Ti 2 O 7 was measured using self-oscillating tunnel-diode resonator. Measurements were made with the excitation AC field parallel to the superimposed DC magnetic field up 5 T in a wide temperature range from 50 mK to 100 K. At 14.6 MHz a known broad peak of χ AC (T ) from kHz -range audiofrequency measurements around 15 K for both [111] and [110] directions shifts to 45 K, continuing the Arrhenius activated behavior with the same activation energy barrier of Ea ≈ 230 K. Magnetic field dependence of χ AC along [111] reproduces previously reported low-temperature two-in-two-out to three-in-oneout spin configuration transition at about 1 T, and an intermediate phase between 1 and 1.5 T. The boundaries of the intermediate phase show reasonable overlap with the literature data and connect at a critical endpoint of the first order transition line, suggesting that these low-temperature features are frequency independent. An unusual upturn of magnetic susceptibility at T → 0 was observed in magnetic fields between 1.5 T and 2 T for both magnetic field directions, before fully polarized configuration sets in above 2 T.