mu SR studies of the nonmagnetic-magnetic transition in YbCu5-xAlx

Chemical pressure was applied to investigate the phase diagram of YbCu5-xAl x(x = 1, 1.5 and 2). The substitution of Cu by Al decreases the fluctuation rate of the Yb magnetic moments. Correlated fluctuations between the Yb ma gnetic moments were evidenced below around 50K in both the YbCu3.5Al1.5 and YbCu3Al2 samples. The YbCu3.5Al1.5 sample is close to a quantum critical p oint, which is evidenced in the mu SR experiment by a continuous increase o f the degree of correlated fluctuations of the Yb magnetic moments as T = 0 K is approached from above. (C) 2001 Elsevier Science B.V. All rights rese rved.