Effect of pressure on thermal expansion of UNiGa

The thermal expansion of single crystalline UNiGa has been measured along the crystallographic axes (a and c) under pressures up to 1.1 GPa. The linear thermal expansion both in the paramagnetic and antiferromagnetic ranges is strongly anisotropic. The antiferromagnetic ordering is accompanied by considerable (10^-4) linear spontaneous magnetostrictions (along the a-and c-axis) of different signs (-0.8 x 10^-4 and 1.8 x 10^-4). The mutual compensation of these two effects causes the volume effect to be rather small (∼10^-5). Two of the four magnetic phase transitions in UNiGa indicated by the expansion anomalies under ambient pressure are suppressed by pressures above 0.5 GPa. Results of our experiments allow to construct a pressure-temperature (p-T) magnetic phase diagram.