Effect of Hydrostatic Pressure on the Low-Temperature Phase Transitions in Rb2ZnBr4

Abstract

The effect of hydrostatic pressure on the low-temperature structural phase transitions in Rb 2 ZnBr 4 has been investigated by the use of neutron scattering technique. The phase III-to-IV transition temperature, T 3 =112 K at atmospheric pressure, increased by applying pressure with a rate of 7 K/kbar. The phase IV-to-V transition temperature, T 4 =76 K at atmospheric pressure, decreased by applying pressure with a rate of -45 K/kbar. At high pressure, two high-order pseudo-commensurate phases characterized by wave vectors q z ≃ \(\frac{3}{11}\) and \(\frac{4}{15}\) were observed in addition to the already known commensurate ones of \(q_z=\frac{2}{7}\) and \(\frac{1}{4}\). The space group of the commensurate phase of \(q_z=\frac{1}{4}\) under high pressure was suggested to be P 2 1 / c 11 from the extinction rule.