@@The two-legged quantum spin ladder NH4CuCl3
has a gapless ground state at zero-field. With increasing field,
the gap opens in the two regions of field, causing the two-stepped
plateaus in magnetization curve. Cu-NMR study under the field
up to 30T has revealed that the spin state consists of discrete
two sets: the singlet site with nearly zero internal field and
excited triplet site with a large internal field. Only the singlet
site is visible in NMR spectra, irrespective of the field being
in or out of the plateaus. The local magnetization of the singlet
site probed by NMR shift showed a different temperature dependence
from that of the macroscopic magnetization. This difference is
explained as the localization of the excited triplets, which
may be the force to open up the finite gap in the plateau region.
In the field out of the plateau, a significant splitting of the
resonance peaks is observed at low temperatures below 4.2 K,
suggesting the existence of the field induced magnetic order.
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Sophia University
: Takayuki Goto, Takao Suzuki
Tokyo Institute of Technology : Hidekazu Tanaka |
IMR, Tohoku
University : Satoshi Awaji, Takahiko Sasaki, Kazuo Watanabe |
Reference : |
S. Hosoya, K. Inokuchi, T. Suzuki, T.
Goto, H. Tanaka, S. Awaji, K. Watanabe, T. Sasaki, T. Fukase,
T. Shimizu, A. Goto,
"NMR study on the quantum spin
ladder NH4CuCl3",
Physica B, in press. |
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