Magnetic phase diagrams are presented for multiaxial structures in cubic DyCu and NdZn in fields up to 26 T applied along the [0 0 11 axis. The numerous phases, clearly delimited by steep magnetization jumps, result from the compromise between Zeeman coupling, magnetic exchange, CEF anisotropy and quadrupolar interaction energies.
The occurrence of multiaxial antiferromagnetic structures is frequent in rare earth compounds of high symmetry [1]. They are characterized by the presence in a given magnetic domain of several propagation vectors, k, from the same crystallographic star. The multi-k arrangement has the same bilinear energy as the collinear single-k structure and is undiscernible from it by neutron diffraction of powder [21. Its existence instead of that of the single-k one needs terms beyond the bilinear one in the Landau expansion of the free energy. These anisotropic couplings are often of quadrupolar type in particular in CsCl-type series with Ag, Cu, Cd and Zn [3]. Although usually dominated by bilinear interactions, they play an important role in the minimization of the free energy in the magnetic phase. When antiferroquadrupolar, these pair interactions are characterized by dispersion curves maximum out of the center of the Brillouin zone and drive the local z axis to change from site to site among the equivalent directions determined by the crystalline electric field (CEF): the structure is then multi-axial with a constant modulus for the magnetic moments. Its field-breaking is characterized by steep jumps of the isothermal magnetization. They correspond to reversals of magnetic moments along their own axis or