LU-PARADOX AS A CONSEQUENCE OF THE DIFFERENT MAGNETIC GROUND-STATES OF THE R(CO,AL)(2) (R=HEAVY RE AND Y) AND LU(CO,AL)(2) COMPOUNDS

The low temperature magnetic characteristics of the Y1-tLut(Co0.88Al0. 12)(2) system were determined. The drastic change from a weakly to str ongly ferromagnetic ground state observed at t = 0.38 is discussed in the itinerant model by using the Landau expression for free energy exp anded up to the eighth power of magnetization. The 'Lu-paradox', that the Curie temperature of Lu(Co1-xAlx)(2) is higher than that of isostr uctural R(Co1-xAlx)(2) with some heavy RE and Y (for x > 0.12), is int erpreted considering the magnetic ground state of the itinerant electr on subsystem to be strongly ferromagnetic in the Lu-based system and w eakly ferromagnetic in the RE-based ones.