Field-induced magnetic order and simultaneous lattice deformation in TlCuCl

Vyaselev, O.*; Takigawa, Masashi*; Vasiliev, A.*; Osawa, Akira; Tanaka, Hidekazu*

We report the results of Cu and Cl nuclear magnetic resonance experiments and thermal expansion measurements in magnetic fields in the coupled dimer spin system TlCuCl. We found that the field-induced antiferromagnetic transition as confirmed by the splitting of NMR lines is slightly discontinuous. The abrupt change of the electric field gradient at the Cl sites, as well as the sizable change of the lattice constants, across the phase boundary indicate that the magnetic order is accompanied by simultaneous lattice deformation. These results suggest the importance of the spin-lattice correlations in this system.