Study of ferroelectric–paraelectric phase transition of RbH2AsO4 single crystals by 87Rb NMR relaxation time measurements

The temperature dependences of the resonance frequency, line width, and spin–lattice relaxation time T1 of the ferroelectric and paraelectric phases of RbH2AsO4 crystals are investigated. The 87Rb NMR line at the phase transition temperature TC (=110 K) splits into two lines, which indicates the occurrence of phase transition from tetragonal to orthorhombic phase. In addition, T1 for the 87Rb nucleus undergoes remarkable changes near TC, which indicates drastic alterations of the spin dynamics at TC. At TC, changes occur in the resonance frequency and T1, which are related to variations in the symmetry of the environments of the 87Rb ions.