Department of Physics,Tarbiat Modares University
Abstract. Based on the instability of magnetic behavior through the concept of local exchange and
hybridization, a new class of heavy fermion is constructed with a stable local magnetic ion, \Gd". The
lattice constant, DC/AC- magnetic susceptibility, (T), and electrical resistivity, (T), measurement
in the magnetic unstable intermetallic compounds of Gd2AxB1????x, show that (I) The hidden magnetic
internal energy is manifested by shape and eld dependence is strongly at x = 0:4, (II) The lattice
parameter of a crystal and magnetic structure, as well as high transition temperature, \Tc", strongly
depends on the conductive electron concentration. Both the functional change of the lattice parameter
(non-Vegard behavior) and magnetic character with electron concentration suggest that the free electrons
are not completely free and are somehow participating in the band functions and magnetic character, and
that (III) There is a coexistence of Kondo behavior and magnetic ordering \re-entrant antiferromagnet"
for x = 0:4 in the range of temperature 30 < Tk < 90 K with TN = Tmax = 30 K, so that (IV) Finally, the
metal insulator-like behavior with a complete quench of magnetic ordering occurs antiferromagnetically,
named superparamagnet, at a certain conductive electron, \x = 0:3", where the sample is eld dependent
(on which , it it is suggested, P"ijJij = 0).
Keyword: Possibility of Kondo eect on \Gd".