STUDY OF THE SPONTANEOUS MAGNETIC PHASES IN TBIN3

The AuCu3-type cubic compound, TbIn3, undergoes below T-N = 32 K a spo ntaneous magnetic transition at T-l = 25 K. The magnetic phase diagram s have been determined from the magnetization curves measured on a sin gle crystal in fields up to 10 T. The corresponding magnetic structure s have been determined from neutron diffraction studies on the same cr ystal under magnetic fields up ta 5 T. For T-l < T < T-N, the spin arr angement is commensurate, q = (1/2, 1/2, 0), and collinear with the sp ins pointing along a fourfold axis. At T-l, the structure remains comm ensurate, but becomes triple q, with the magnetic moments pointing alo ng the threefold axes. The crystalline electric field (CEF) parameters have been deduced by analysing the magnetic and magnetostrictive prop erties of the (Tb0.02Y0.98)ln(3) dilute compound, within the CEF susce ptibility formalism. Calculations within the mean-field approximation, taking account of CEF, bilinear and quadrupolar interactions, ate pre sented, which describe quantitatively the properties of TbIn3 in the l ow-held region.