Magnetic field effect on the magnetic torque and the magnetostriction in (CH₃)₂CHNH₃CuCl₃

Magnetic torque τ and magnetostriction ΔL/L measurements were carried out in the spin gap system (CH₃)₂CHNH ₃CuCl₃. The magnetic torque shows a cusp-like anomaly at the magnetic field H_a1with increasing the magnetic field, and the magnetostriction shows a kink at almost the same magnetic field. These results suggest that anomalous change in the magnetic torque is associated with the lattice distortion, and it is expected that the field-induced magnetic phase transition is not simple Bose-Einstein condensation in this system.