Specific heat measurements down to 120mK have been performed on a quasi-one-dimensional S=1/2 spin-gapped system (CH3)2NH2CuCl3 in a magnetic field up to 8 T. This compound has a characteristic magnetization curve which shows a gapless ground state and a plateau at 1/2 of the saturation value. We have observed a spontaneous antiferromagnetic ordering and a field-induced one below and above the 1/2 plateau field range, respectively. The field versus temperature phase diagram is quite unusual and completely different from those of the other quantum spin systems investigated so far. In the plateau field range, a double-structure in the specific heat is observed, reflecting the coexistence of ferromagnetic and antiferromagnetic excitations. These behaviors are discussed on the basis of a recently proposed novel quantum spin chain model consisting of weakly coupled ferromagnetic and antiferromagnetic dimers.
@article{arxiv.cond-mat/0508007,
title = {Specific Heat Study on a Novel Spin-Gapped System : (CH_3)_2NH_2CuCl_3},
author = {Yasuo Yoshida and Osamu Wada and Yuji Inagaki and Takayuki Asano and Kenji Takeo and Tatsuya Kawae and Kazuyoshi Takeda and Yoshitami Ajiro},
journal= {arXiv preprint arXiv:cond-mat/0508007},
year = {2009}
}
Comments
4 pages, 3 figures, submitted to J. Phys. Soc. Jpn