Chiatti, O; Sytcheva, A; Wosnitza, J; Zherlitsyn, S; Zvyagin, AA; Zapf, VS; Jaime, M; Chiatti, O; Sytcheva, A; Wosnitza, J; Zherlitsyn, S; Zvyagin, AA; Zapf, VS; Jaime, M; Paduan-Filho, A; - view fewer (2008) Spin-strain coupling in NiCl2-4SC(NH2)2. Presented at: Deutsche Physikalische Gesellschaft (DPG) Spring Meeting 2008, Technischen Universität Berlin, Berlin, Germany.

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Abstract

We report results of ultrasonic investigations of the quantum S = 1 spin-chain magnet NiCl2-4SC(NH2)2, also known as DTN, in magnetic fields up to 18 T and temperatures down to 0.3 K. A field H along the [001] direction induces a transition into an antiferromagnetic phase with T(N)max ≈ 1.2 K. Accordingly, at T = 0 there are two quantum critical points at ~2.1 T and at ~12.6 T. The acoustic c33 mode, propagating along the spin chains, shows a pronounced softening close to the phase transition, accompanied by energy dissipation of the sound wave. The H-T phase diagram obtained from our measurements is compared with results from other experimental investigations and the low-temperature acoustic anomalies are traced up to T > T(N). We also report frequency-dependent effects, which open the possibility to investigate the spin fluctuations in the critical regions. Our observations show an important role of the spin-phonon coupling in DTN.

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