Conductivity anisotropy and hot electron temperature in silicon : W.E.K. Gibbs (Australian Defense Scientific Service, Department of Supply, Defence Standards Laboratories, Maribyrnong, Victoria, Australia)

Abstract

The superconducting phase diagrams for primitive tetragonal (pt) R(Rh1−xIrx)4B4 and body centered tetragonal (bct) R(Rh1−xRux)4B4 have been measured down to 4 mK revealing the characteristic drop of Tc for x⩾xcr. For pseudoternary R(Rh1−xRux)4B4 high resolution photoemission spectra clearly a shift of EF to lower energies upon alloying Ru for Rh. From a comparison between the experimental data and bandstructure calculations it can be concluded that variations of N(EF) connected with this shift are the underlying mechanism for the observed Tc(x) behavior. Contrary to this, the spectra forR(Rh1−xIrx)4B4 reveal a broadening and an increasing bandwidth of the transition metal d-band originating from the more extended 5d-wavefunctions of Ir. A numerical simulation of this broadening implies that the restriction of a constant number of occupied states leads to a shift of EFto higher energies. This results in a decrease of N(EF) and Tc. In addition to the peculiar superconducting phase diagram inHo(Rh1−xRux)4B4 a change in magnetic order from antiferromagnetism for x<xcr to ferromanetism for x close to 1 is observed by neutron scattering. Whereas in case of x=0.90 and 1.00 the magnetic phase can be described by a superposition of a ferromagnetic and an antiferromagnetic component, the sample with x=0.10 orders magnetically at 1.5 K with a complicated acollinear antiferromagnetic structure.