Modulated magnetic structure of U(Pd1-xFex)(2)Ge-2 studied by mu SR

The magnetic ordering of the ternary intermetallic compound U(Pd1-xFex)(2)G e-2 (x = 0.01, 0.02) was studied by mu SR in the temperature range T = 15-3 00 K. The low temperature state changes from the modulated longitudinal spi n density wave LSDW (x = 0.01) with a propagation vector k = [003/4] (T-N = 140 K) to a simple antiferromagnetic structure AF (x = 0.02) with K = [001 ] (T-N = 140 K). In the AF phase (sample with x = 0.02) the uranium magneti c moment shows a monotonic temperature dependence. In the LSDW phase with k = [003/4] (sample with x = 0.01) the magnetic moments of uranium atoms loc ated in two magnetically nonequivalent positions (000)and (001) have differ ent temperature dependences. One moment assumes a maximum at T-m1 = 50 K, w hile the other one does not display any peculiarities. The results are disc ussed within a model of the superposition of a square and sine modulation a nd are compared with neutron diffraction data. The observed peculiar temper ature behaviour of the moments is connected with the temperature variation of the initial phase phi of the LSDW modulation by Delta phi = 0.2 rad.