Low-temperature magnetization study of spin gap system (CH ₃)₂NH₂CuCl₃ with nanometer particle size

So far specific heat measurements for the title compound have revealed that the magnetic field vs. temperature phase diagram depended significantly on the system size. For instance, the single crystal showed the spontaneous magnetic ordered phase in low fields and the field induced one in high fields separated by the magnetization plateau range at around 3 T, while the powder sample with typically nanometer particle size showed a quite different trend that field induced magnetic ordered phase extended to zero field. In this study, we measures dc magnetization of powder sample and nano-sized powder sample. Measurements were performed down to the lowest temperature of 0.5 K using commercial Quantum Design MPMS equipped with homemade ³He refrigerator insert. Most remarkable feature is that 1/2 plateau was not observed clearly in the magnetization process for the nano-sized powder sample indicating the disappearance of the spin gap.