Abstrakt
We report on the evolution of magnetic properties in the PrNi1-xCuxAl series investigated by measurements of magnetization, AC susceptibility, specific heat, and powder neutron diffraction. For compounds with a low Cu content, we observe antiferromagnetic incommensurate structures characterized by propagation vector k = (1/20q) having q = 0.416 +/- 0.002 and 0.428 +/- 0.006 in the case of x = 0.1 and 0.2, respectively.
A commensurate antiferromagnetic structure with k = (1/20 1/2) then appears in compounds with x = 0.4 and 0.5, which is followed by a spin-glass state with short-range correlations in the Cu-rich part of the series. The short-range magnetic correlations have an antiferromagnetic character with a propagation vector close to the one observed in the magnetically ordered PrCuAl.
Investigations of the spin relaxation phenomena by use of the frequency-dependent AC susceptibility revealed that a spin-glass-like state develops at low temperatures with evidence of collective clustering. A crystal-field energy scheme, deduced from specific heat data, is characterized by a quasidoublet ground state in the whole series.