Magnetic properties of rare-earth transition metal aluminides R6T4Al43 with Ho6Mo4Al43-type structure

The magnetic properties of 53 aluminium-rich intermetallic compounds R6T4Al 43 with R = rare-earth elements and T = Ti, V, Nb, Ta, Cr, Mo, W were inves tigated using polycrystalline samples and a SQUID magnetometer in the tempe rature range from 2 to 300 K with magnetic flux densities up to 5.5 T. The yttrium and lutetium compounds are Pauli paramagnetic, indicating that the transition metal atoms do not carry magnetic moments. The samarium compound s show van Vleck behavior and antiferromagnetic order with Neel temperature s of less than 12 K. Of these Sm,Ti,Al,, becomes metamagnetic. The ytterbiu m compounds show a mixed or intermediate valent behavior and no magnetic or der down to 2 It. All other compounds obey the Curie-Weiss law above 30 K. Their effective magnetic moments correspond to the theoretical moments of t he rare-earth ions. They show ferromagnetic or metamagnetic behavior with o rdering temperatures all below 20 K. The magnetization curves of most compo unds (recorded up to 5.5 T) reach about 50% of the theoretical magnetizatio n already at 0.5T. The gadolinium compounds are exceptional in that they re ach at 0.5 T only about 10% of their theoretical magnetization. The crystal structures of the isotypic compounds Yb6V4Al43 and Yb6Ta4Al43 were refined from single-crystal X-ray data. (C) 2001 Elsevier Science B.V. All rights reserved.