Magnetic and electrical properties of Sc(M1-xSix)2-y (M=Fe, Co, Ni)

Structural and magnetic properties of the binary compound ScFe2-y (MgZn2-type structure) and ternary compounds Sc(Fe0.94Si0.06)(1.86) (MgCu2-type structure), Sc(Fe0.75Sio.75)(2), Sc(Co0.75Si0.25)(2) and Sc(Ni0.75Si0.25)(2) (MgZn2-type structure), were studied. Only in the Fe based compounds does long range ferromagnetic order exist. In the pseudobinary system, Sc(Fe1-xSix)(2-y), both the Fe moment and the Curie temperature decrease with increasing Si-concentratjon. This is accounted for by changes of the electronic structure. The substitution by Si has no significant influence upon the lattice parameters. In this case, however, when Sc(Fe0.75Si0.25), and Sc(Co0.75Si0.25)(2) are compared to ScFe2, an anomalous increase of the electrical resistivity in the whole temperature range is observed, for the Fe compound even yielding a negative slope. Both the large resistivity values and the enhancement of the electronic specific heat (compared to ScFe2 by a factor of three) due to the substitution are attributed to an increase of the density of states at the Fermi energy N(E-F). When comparing ScFe2 with Sc(Fe0.75Si0.25), by Mossbauer spectroscopy, a modest reduction of the electron density at the Fe-57 site of approximate to 0.1 s-electrons is observed. Thus, from the specific heat results, a significant increase of the d-density of states at E-F has to be concluded. (C) 1998 Published by Elsevier Science S.A. All rights reserved.