Glassy behavior in a metal-organic perovskite, dimethylammonium zinc formate [(CH3)2NH2][Zn(HCOO)3]

Proton spin-lattice relaxation was reinvestigated of a metal-organic perovskite [(CH3)2NH2][Zn(HCOO)3] in the low-temperature range down to 10 K, in order to elucidate the origin of a first-order phase transition like behavior previously observed at around 79 K. Below about 70 K, the magnetization recovery was non-exponential and analyzed assuming a stretched exponential relaxation. The stretching exponent β was determined as 0.6 below 40 K, indicating the distribution of the spin-lattice relaxation time T1 and the growth of inhomogeneity in the crystals. The thermal hysteresis previously observed at around 79 K is expected not due to a first-order phase transition but non-equilibrium phenomena related to glass state.