Magnetic properties of icosahedral R-Mg-Zn quasicrystals (R=Y, Tb, Dy, Ho and Er)

Large (up to 0.5 cm(3)) single grains of icosahedral R-Mg-Zn quasicrystals (R=Y, Tb, Dy, Ho and Er) have been grown via a self-flux technique. The sam ples have a composition of approximately R9Mg34Zn57, and are extremely well -ordered, with little or no evidence of phason strain. These samples have a llowed a detailed investigation of the magnetic behaviour of local 4f momen ts in a quasiperiodic environment. Neutron scattering experiments using pow dered single-grains show no evidence for long range magnetic order in the R -Mg-Zn quasicrystals. However, magnetization and magnetic susceptibility me asurements indicate a spin-glass state, with freezing temperatures T-f = 5. 8, 3.6, 2.0 and 1.3 K for R = Tb, Dy, Ho and Er respectively. Deviations fr om a Curie-Weiss temperature dependence of the susceptibility are small, an d only occur for temperatures up to 5 K above T-f, indicating the absence o f any significant cluster glass behaviour. In addition, the rare earth dilu tion series (Y1-xGdx)-Mg-Zn have lower freezing temperatures than (Y1-xTbx) -Mg-Zn, despite the larger de Gennes factor of Gd3+ over Tb3+, indicating t hat crystal electric fields play a significant role in the freezing phenome non. This difference between Heisenberg and non-Heisenberg moments is furth er explored via several (Gd1-xRx)-Mg-Zn pseudo-ternary quasicrystal series. (C) 2000 Elsevier Science S.A. All rights reserved.