TY - JOUR

T1 - NMR

AU - Endo, S.

AU - Goto, T.

AU - Fukase, T.

AU - Uozaki, H.

AU - Okamoto, K.

AU - Toyota, N.

N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.

PY - 1998

Y1 - 1998

N2 - We report (Formula presented) measurements on a single crystal of superconducting (Formula presented) where (Formula presented) is bis(ethylenedithiotetrathiafulvalene), (Formula presented) The temperature dependence of the spectrum has revealed that two phase transitions occur on cooling; first at (Formula presented) where a single resonance peak splits into two subpeaks, and second at (Formula presented) where the subpeaks disappear after the broadening at 25 K. The former associated by temperature hysterisis is a first-order phase transition and the splitting width follows (Formula presented) dependence. This splitting, which is so sensitive to the field orientation due to (Formula presented) is found to be caused by the quadrupole interaction. The spin-lattice relaxation rate (Formula presented) is strongly elongated by three orders of magnitude with decreasing temperature from 200 K, followed by the maximum around 40 K. This dramatic effect is interpreted by the Bloembergen-Purcell-Pound model applied to the quadrupole interaction. Discussions are made from the viewpoint of the dynamics of noncentrosymmetric tetrahedral molecule (Formula presented) at (Formula presented) the uniform rotation might switch to the thermally activated hopping motion between preferable sites bonded to nitrogens of (Formula presented) legands and then the order-disorder transition might eventually occur at (Formula presented) to form an anion ordering.

AB - We report (Formula presented) measurements on a single crystal of superconducting (Formula presented) where (Formula presented) is bis(ethylenedithiotetrathiafulvalene), (Formula presented) The temperature dependence of the spectrum has revealed that two phase transitions occur on cooling; first at (Formula presented) where a single resonance peak splits into two subpeaks, and second at (Formula presented) where the subpeaks disappear after the broadening at 25 K. The former associated by temperature hysterisis is a first-order phase transition and the splitting width follows (Formula presented) dependence. This splitting, which is so sensitive to the field orientation due to (Formula presented) is found to be caused by the quadrupole interaction. The spin-lattice relaxation rate (Formula presented) is strongly elongated by three orders of magnitude with decreasing temperature from 200 K, followed by the maximum around 40 K. This dramatic effect is interpreted by the Bloembergen-Purcell-Pound model applied to the quadrupole interaction. Discussions are made from the viewpoint of the dynamics of noncentrosymmetric tetrahedral molecule (Formula presented) at (Formula presented) the uniform rotation might switch to the thermally activated hopping motion between preferable sites bonded to nitrogens of (Formula presented) legands and then the order-disorder transition might eventually occur at (Formula presented) to form an anion ordering.

UR - http://www.scopus.com/inward/record.url?scp=0345302282&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0345302282&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.57.14422

DO - 10.1103/PhysRevB.57.14422

M3 - Article

AN - SCOPUS:0345302282

VL - 57

SP - 14422

EP - 14427

JO - Physical Review B - Condensed Matter and Materials Physics

JF - Physical Review B - Condensed Matter and Materials Physics

SN - 0163-1829

IS - 22

ER -