Effect of uniaxial stress on the 130 k and 93 k phase transitions in k₂seo₄

The uniaxial stress dependencies of the 130 K(T_i) and 93 K(T_c) transitions in K₂SeO₄ were determined from measurements of birefringence anomalies at T₁, and capacitance anomalies at T_c. At T₁ for crystal axes defined as c<a<b, we obtain: -17.0±0.2 K/kbar for stress along “c”, 3.1 ±0.2 K/kbar for stress along “a”, and 7.7 ± 0.2 K/kbar for stress along “b”. Summing these three values gives the hydrostatic pressure dependence of -6.2 K/kbar, close to the reported experimental values of about -6.5 K/kbar. Capacitance vs temperature data, for stress along “c” only, in the vicinity of 93 K were fitted to a Curie-Weiss law to determine the transition temperatures. A value of about -25K/kbar for the oaxis stress dependence of T_c was found.