FERRIMAGNETISM IN U(CO0.5NI0.95)(2)SI-2 AND U(NI0.95CU0.05)(2)SI-2

A neutron-diffraction study of U(Co1-yNiy)(2)Si-2 and U(Ni1-zCuz)Si-2 solid solutions in the vicinity of UNi2Si2 shows that the ferrimagneti c (+ + -) phase with k = (0, 0, 2/3) of the latter is observed also fo r materials with y = 0.95 and z = 0.05, below the AF-I phase with k = (0, 0, 1). This ferrimagnetism exists below 50 +/- 4 K in U(Co0.05Ni0. 95)(2)Si-2, with U moment of 1.75 +/- 0.11 mu(B) at 12 K, and coexists with an AF-I phase below 37 +/- 5 K in U(Ni0.95Cu0.05)(2)Si-2, with U moment of 1.79 +/- 0.15 mu(B) at 12 K. The ferrimagnetic phase extend s between y approximate to 0.93 and z approximate to 0.03. Its abrupt appearance upon a minor change in conduction-electron concentration is attributed to RKKY-like interactions. (C) 1998 Elsevier Science B.V. All rights reserved.