M. Kuznietz et al., 3 COMMENSURATE MAGNETIC-STRUCTURES IN THE SOLID-SOLUTION U(NI0.25CU0.75)2SI2, OBSERVED BY NEUTRON-DIFFRACTION, Physical review. B, Condensed matter, 50(6), 1994, pp. 3822-3827
A polycrystalline sample of the solid solution U(Ni0.25Cu0.75)2Si2 Was
prepared and found to have the tetragonal ThCr2Si2-type crystallograp
hic structure. The observation of a ferrimagnetic transition at 112 +/
- 5 K by ac-susceptibility measurements, is confirmed by neutron diffr
action, which also indicated three commensurate magnetic structures (b
elow almost-equal-to 110 K). Two structures are antiferromagnetic (AF)
, 40% each, and one is ferrimagnetic, 20% in volume. The structures ar
e AF-I (+ - + -), ferrimagnetic (+ + -), and AF-IA (+ + - -), with wav
e vectors k = (0, 0, 1), (0, 0, 2/3), and (0, 0, 1/2), and T(N) = 120
+/- 3, 115 +/- 4, and 110 +/- 3 K, respectively. The uranium ordered m
agnetic moments (2.2 +/- 0.1 mu(B) at 1.5 K) are along the tetragonal
axis in all three structures. These phases fit well into the proposed
magnetic phase diagram of the U(Ni1-xCux)2Si2 system, and are compared
with corresponding solid solutions in the parallel U(Ni1-xCux)2Ge2 sy
stem.