μSR study on quantum spin system NH4CUCl3

K Matsui,K Yoshizawa,H Tanaka,T Suzuki,I Watanabe,A Oosawa,T Goto,P K Biswas,M Fujisawa,A Amato

doi:10.1088/1742-6596/551/1/012007

K Matsui, K Yoshizawa + Show 8 more

Open Access

https://doi.org/10.1088/1742-6596/551/1/012007

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Abstract

The quantum spin dimer system NH4CuCl3 has a gapless ground state with TN = 1.3 K, and shows plateaus in the high-field magnetization at 1/4 and 3/4 of the saturation magnetization, the mechanism of which has not yet been resolved until now. The three dimer model recently proposed by Matsumoto, which seems well accounting for the emergence of plateaus, predicts the existence of three magnetically-inequivalent dimers. In order to test the model, we have measured transverse-field (TF) muon depolarization curves. In fourier transform of TF muon depolarization curves, we observed homogeneous single peak at T > 100 K. Below 70 K, the peak showed rapid broadening, and split into multiple peaks in still lower temperatures, supporting the idea of the three dimer subsystems.

Highlights

Quantum spin systems have been attracting much interests in last two decades both experimentally and theoretically, because these systems exhibit numerous peculiar magnetic features, as represented by the triplon Bose-Einstein Condensation (BEC) in spin gap systems[1, 2] and the magnetization plateaus[3], which cannot be interpreted by conventional classical spin vector models
A finite energy is needed to create an additional triplon, i.e. dn/dμ = 0, where n is the total triplon density corresponding to the magnetization M in the original spin
Observed TF muon depolarization curves are shown in Fig. 2, where one can clearly see the muon spin rotation with a frequency approximately 66.4 MHz in the TF of H0 = 0.49 T

Summary

Introduction

Quantum spin systems have been attracting much interests in last two decades both experimentally and theoretically, because these systems exhibit numerous peculiar magnetic features, as represented by the triplon Bose-Einstein Condensation (BEC) in spin gap systems[1, 2] and the magnetization plateaus[3], which cannot be interpreted by conventional classical spin vector models. System so that the magnetization plateau emerges in the superlattice phase. Such superlattice of triplons has been observed in the orthogonal dimer system SrCu2(BO3)2[10] at the 1/8-plateau phase[11, 12].

Results

Conclusion