Study of magnetic excitation in singlet-ground-state magnets CsFeCl3 and RbFeCl3 by nuclear magnetic relaxation

• Published in: Journal of the Physical Society of Japan 2002-03, Vol.71 (3), p.930-942
• Main Authors: TODA, Mitsuru, GOTO, Takao, CHIBA, Meiro, SUZUKI, Naoshi
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Magnetically ordered materials: other intrinsic properties; Nuclear magnetic resonance and relaxation; Physics; Relaxation effects; Spin waves
• ISSN: 0031-9015; 1347-4073
• DOI: 10.1143/JPSJ.71.930

The temperature dependences of spin-lattice relaxation time T1 of 133Cs in CsFeCl3 and 87Rb in RbFeCl3 were measured in the temperature range between 1.5 K and 22 K, at various fields up to 7 T applied parallel (or perpendicular) to the c-axis, and the analysis was made on the basis of the dynamical correlated-effective-field approximation. The mechanism of the nuclear magnetic relaxation is interpreted in terms of the magnetic fluctuations which are characterized by the singlet ground state system. In the field region where the phase transition occurs, T1-1 exhibited the tendency of divergence near TN, and this feature was ascribed to the transverse spin fluctuation associated with the mode softening at the K-point. It was found that the damping constant of the soft mode is remarkably affected by the occurrence of the magnetic ordering at lower temperature, and increases largely in the field region where the phase transition occurs.