SPIN-GLASS BEHAVIOR OF ICOSAHEDRAL MG-GD-ZN AND MG-TB-ZN QUASI-CRYSTALS

The magnetic properties of icosahedral Mg(42)RE(8)Zn(50) (RE = Gd, Tb, Dy, Ho or Er) quasi-crystals have been investigated. These quasi-crystalline phases have a face-centred icosahedral lattice with a highly ordered Frank-Kasper-type structure as identified by electron diffraction and x-ray diffraction. The temperature dependence of Dc magnetic susceptibility obeys a Curie-Weiss law in wide temperature ranges. The effective magnetic moments mu(eff) are close to those of free RE(3+) ions and their paramagnetic Curie temperature Theta(p) is negative, indicating that the RE-RE exchange interactions are predominantly antiferromagnetic. The value of Theta(p) which is the sum of all exchange interactions is almost in proportion to the de Gennes factor. At low temperatures, spin-glass behaviour has been observed in the icosahedral Mg42Gd8Zn50 and Mg42Tb8Zn50 quasi-crystals and their spin freezing temperatures T-f are 5.5 K and 7.6 K, respectively.