MAGNETIC AND ELECTRICAL-PROPERTIES OF SC(M1-XSIX)(2-Y) (M=FE, CO, NI)

Structural and magnetic properties of the binary compound ScFe2-y (MgZ n2-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 base d compounds does long range ferromagnetic order exist. In the pseudobi nary system, Sc(Fe1-xSix)(2-y), both the Fe moment and the Curie tempe rature decrease with increasing Si-concentratjon. This is accounted fo r by changes of the electronic structure. The substitution by Si has n o significant influence upon the lattice parameters. In this case, how ever, when Sc(Fe0.75Si0.25), and Sc(Co0.75Si0.25)(2) are compared to S cFe2, an anomalous increase of the electrical resistivity in the whole temperature range is observed, for the Fe compound even yielding a ne gative 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 elect ron density at the Fe-57 site of approximate to 0.1 s-electrons is obs erved. Thus, from the specific heat results, a significant increase of the d-density of states at E-F has to be concluded. (C) 1998 Publishe d by Elsevier Science S.A. All rights reserved.