Pressure-Induced Antiferroelectricity in Ferroelectric Cs${\mathrm{H}}_2$P${\mathrm{O}}_4$

A new phase in Cs${\mathrm{H}}_2$P${\mathrm{O}}_4$ is induced by pressures above about 3.3 kbar; this phase is confirmed to be antiferroelectric by the observation of $P-E$ double hysteresis loops. The qualitative change from the paraelectric-ferroelectric to the paraelectric-antiferroelectric transition caused by the pressure is interpreted to originate in the one-dimensional characteristics with the chainlike ordering of the hydrogen bound along the $b$ axis in Cs${\mathrm{H}}_2$P${\mathrm{O}}_4$.