The giant magnetoresistance of Co/Cu superlattices grown by MBE

We report the first observation of a giant magnetoresistance (MR) in Co/Cu superlattices grown by MBE. The maximum value of the MR is - 26% and this is found in a specimen for which the copper layers are about 7 Å thick and which includes a thin 10 Å layer of gold in the buffer region between the substrate and the superlattice. From RHEED and X-ray diffraction it is shown that the metallic layers in the specimens grown in this way are extremely flat and that the orientation of the copper is (111).     

Role of interface scattering on the giant magnetoresistance of magnetic multilayers

A discussion is presented of the effect of interface scattering on the giant magnetoresistance of magnetic multilayers. It has recently been found experimentally that increased interface scattering causes the magnetoresistance to increase for Fe/Cr multilayers, but to decrease for Co/Cu multilayers. An explanation is proposed for this striking difference in behaviour for these two systems.     

Auger electron spectroscopic measurements of ZnCl2-coal interaction

Two anolomous peaks in the ZnL₃M₂,₃M_4,5 Auger electron spectra of dried and heated samples of ZnCl₂-coal mixtures have been interpreted as indication of a Zn-coal bond formation. The peaks show a decrease from the normal 9.1 eV splitting for ZnCl₂ alone to 4.2 eV for ZnCl₂-coal mixtures. High volatile bituminous coals show this effect to a greater extent than either higher or lower rank coals. It is surmised that the side of this bond formation could coincide with the site of catalytic activity in the catalytic hydrogenation of coal in the presence of ZnCl₂.     

Mean free path effects on the current perpendicular to the plane magnetoresistance of magnetic multilayers

We have carried out an experimental and theoretical study of the magnetoresistance MR(H) in the CPP (current perpendicular to the planes) mode for two types of magnetic multilayers that differ only in the ordering of the magnetic layers: [Co(10 A)/Cu(200 A)/Co(60 A)/Cu(200 A)](N) and [Co(10 A)/Cu(200 A)](N)[Co(60 A)/Cu(200 A)](N). The series resistor model predicts that in the CPP mode MR(H) is independent of the ordering of the layers. Nevertheless, the measured MR(H) curves were found to be completely different for the two cases. Calculations based on a realistic band structure and the Kubo formula show that the results are a consequence of a long mean free path.     

Role of the phonon trial function in determining the phonon-drag contribution to the low-temperature electrical resistivity

It is demonstrated that there is excellent agreement between the low-temperature electrical resistivity data for potassium and the Bailyn formulation for the phonon-drag electrical resistivity, which is based on a consistent solution for the phonon trial function in terms of the electron trial function.     

Evidence that the Born approximation is unreliable for calculating transport coefficients of liquid metals

The validity of the Born approximation formula for the electrical resistivity of a liquid metal has recently been questioned by Greenfield. However, it has been suggested that Greenfield underestimated the volume dependence of the potential. We demonstrate that the influence of the volume dependence of the potential is indeed small, and we thus confirm Greenfield's conclusion that the Born approximation formula fails to give the correct temperature dependence of the resistivity. This failure is shown to occur both for the constant-pressure and for the constant-volume cases.