Electronic properties of PrNi1−xCuxAl compounds

Abstract

We report on the evolution of magnetic properties in the PrNi${}_{1\ensuremath{-}x}$Cu${}_{x}$Al 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 $k=(1/2\phantom{\rule{0.16em}{0ex}}0\phantom{\rule{0.16em}{0ex}}q)$ having $q$ = 0.416 $\ifmmode\pm\else\textpm\fi{}$ 0.002 and 0.428 $\ifmmode\pm\else\textpm\fi{}$ 0.006 in the case of $x=0.1$ and 0.2, respectively. A commensurate antiferromagnetic structure with $k=(1/2\phantom{\rule{0.16em}{0ex}}0\phantom{\rule{0.16em}{0ex}}1/2)$ 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.