Pressure effects on antiferromagnetism in UNiAl

The temperature dependencies of the electrical resistivity rho for current along and perpendicular to the c axis were measured on single crystalline U NiAl under various hydrostatic pressures. The rho(T) curves at ambient pres sure exhibit a Cr anomaly around the Neel temperature T-N. Application of p ressure causes a reduction of T-N value. Linear extrapolation of low-pressu re T-N vs p data yields an estimate of a critical pressure for antiferromag netism p(c)approximate to 10 GPa. Measurements above 1 GPa, however, reveal a collapse of the antiferromagnetic (AF) ordering already below 3 GPa, alt hough AF correlations seem to affect resistivity behavior rho(T) in pressur es up to 8 GPa. A sudden change of the rho(T) curve character for i perpend icular to c and T < T-N indicates a pressure-induced change of magnetic ord ering or fluctuations within the basal plane. The results are discussed in terms of the instability of the itinerant 5f-electron antiferromagnetism in UNiAl. (C) 2000 American Institute of Physics. [S0021-8979(00)65108-3].