MAGNETIC-PROPERTIES OF CUBIC R(X)Y(1-X)AL(2) (R=DY, TB) INTERMETALLIC RANDOM ANISOTROPY MAGNETS

A short review is made of the key magnetic properties of dilute cubic RxY1-xAl2 (R=Tb, Dy) intermetallics, in order to show their main magnetic features. Dilution by Y introduces a weak random magnetic anisotropy (RMA). The rich magnetic phase diagram is described, including paramagnetic (P), spin glass (SG), correlated spin glass (CSG), random ferromagnetic (RFM), and ferromagnetic (F) phases, with a triple point and two multicritical ones. The paper deals with the induced macroscopic magnetic anisotropy cooling in a magnetic field below TSG or TCSG transition temperatures, which can be either unidirectional or uniaxial or both. High-field (3 T) magnetostriction in Tb series shows, for x=0.48, 0.59, 0.87, a decrease of the Callen α exponent (λt∼m α, m=reduced magnetization) below 3. The Sompolinsky irreversibility parameter Δ has been determined for the Tb series in the SG regime, and a replica model is presented to explain the Δ(T) dependence. The character of the P→SG or P→CSG transitions is addressed, through the scaling of nonlinear susceptibility (SG regime) or a ferromagnetic-like scaling of magnetization, respectively. From quasielastic neutron scattering around Q=[1,1,1] we determine the temperature dependence of the magnetic correlation length in Dy0.8Y0.2Al 2, which peaks, but does not diverge at Tc. A magnon excitation at 3.5 meV is reported for x=0.8.