Magnetic structure of DyCu2 in the virgin and in the converted state

The orthorhombic intermetallic compound DyCu2 shows below T-N = 27 K a comp lex magnetic-phase diagram due to RKKY interaction in combination with a st rong crystal field anisotropy. In the easy a-direction the low-field antife rromagnetic structures AF1 (commensurate) and AF2 (incommensurate sinusoida l modulated) were determined with wave vectors tau = (2/3 10) and tau* = (0 .6510), respectively. In an external magnetic field parallel to a with 1.6 T < mu(0)H < 2.0 T a phase F1 exists with the same tau = (2/3 10) as AF1 bu t with the higher harmonic 2 tau instead of 3 tau in AF1 which corresponds to a ferromagnetic modulation. In strong magnetic fields parallel to the c- direction DyCu2 undergoes a conversion of the easy axis from a- into c-dire ction. This conversion remains stable after switching off the field., After the conversion the magnetic structures in fields parallel to c are similar to those measured in the virgin state in fields parallel to a. (C) 2000 El sevier Science B.V. All rights reserved.