MAGNETIC PHASE-DIAGRAM IN NDIN3 ANTIFERROMAGNET

The NdIn3 compound, which crystallizes in the AuCu3-type cubic structure, orders antiferromagnetically at T(N) = 5.9 K. In zero-field it undergoes two successive first-order magnetic transitions at T1 = 5.2 K and T2 = 4.7 K. Just below T(N), the magnetic structure is sine modulated, q over arrow pointing right = (1/2,1/2,0.036), at T1 the structure squares up with a propagation vector q over arrow pointing right = (1/2,1/2,0.017), before to stabilize into the commensurate q over arrow pointing right = (1/2,1/2,0) below T2. In these three single-q over arrow pointing right phases, the magnetic moments remain aligned along the fourfold axis. We present here an extensive study in the whole antiferromagnetic range, by magnetization measurements in fields up to 14 T and by neutron diffraction up to 10 T. Along the three high symmetry axes of the crystallographic structure, the magnetization presents numerous metamagnetic transitions. The corresponding (H-T) magnetic phase diagrams have been determined. In particular, the [001] phase diagram reveals the existence at low temperatures of two high-field induced magnetic phases. Surprisingly, in these phases, the most probable magnetic arrangements arc multi-q over arrow pointing right structures, with q over arrow pointing right belonging to the [1/2,1/2,0] crystallographic star. As for the low-temperature commensurate structure, the magnetic moments keep pointing along the fourfold axes and the field-induced transitions arc explained by the successive flips of two moments towards the direction of the field.