The evolution from long-range magnetic order to spin-glass behaviour in PrAu2(Si1-xGex)(2)

We have studied the magnetic behaviour of PrAu2(Si1-xGex)(2) by means of ma gnetic susceptibility, resistivity, and heat capacity measurements, and x-r ay and neutron powder diffraction. All compounds are isostructural and crys tallize in the well known ThCr2Si2-type structure. PrAu2Si2 shows the chara cteristic features of a canonical spin glass with a freezing temperature of T-F = 3 K. Completely unexpectedly on introducing/increasing the atomic di sorder by alloying with Ge, the spin-glass transition is suppressed as is f irst evident from a slight decrease of the freezing temperature TF UP to x = 0.10. Long-range magnetic order sets in for x greater than or equal to 0. 12. Within the range 0.15 less than or equal to x less than or equal to 1, all compounds show the same simple AF-I-type antiferromagnetic structure wi th a monotonic increase of both the Neel temperature and the ordered magnet ic moment for increasing Ge concentration. The magnetic phase diagram of Pr Au2(Si1-xGex)(2) is explained by the presence of weak disorder at a constan t level at the Au sites. Clear indications of crystal-field effects have be en observed.