Biomedical subjects

DG Pettifor

Publications and source records attributed to DG Pettifor.

13 recordsLinked to original sources

PubMed2000

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.

Journal Article↗

PubMed2000

Bounded analytic bond-order potentials for sigma and pi bonds

Novel analytic bond-order potentials (BOP's) are derived for the sigma and pi bonds of sp-valent systems that are correctly bounded from above by unity. We show that these BOP's allow the concept of single, double, triple, and conjugate bonds in carbon systems to be quantified, the average error compared to accurate tight-binding predictions being only 1% for the sigma bonds and 15% for the pi bonds. Although molecular dynamics simulations are an order of magnitude slower than with standard Tersoff potentials, these new BOP's provide the first "classical" interatomic potentials that handle both structural differentiation and radical formation naturally within its framework.

Journal Article↗

PubMed1996