Tat-Sang Choy | Searcharxiv

arXiv2002

A Theoretical Search for the Optimum Giant Magnetoresistance

The maximum current-perpendicular-to-plane giant magnetoresistance is searched for in magnetic multilayers made of Co, Ni, and Cu with disorder levels similar to those found in room temperature experiments. The calculation is made possible by a highly optimized linear response code, which uses the impurity averaged Green's function technique and a 9-band per spin tight binding model. Using simulated annealing, hundreds of different configurations of the atomic layers are examined to find a maximum GMR of 450% in ultrathin Ni/Cu superlattices.

cond-mat.mtrl-sci↗

arXiv1999

Correlation between Spin Polarization and Magnetic Moment in Ferromagnetic Alloys

The correlation between the magnetic moment in ferromagnetic alloys and the tunneling spin polarization in ferromagnet-insulator-superconductor tunneling experiments has been a mystery. The measured spin polarization for Fe, Co, Ni, and various Ni alloys is positive and roughly proportional to their magnetic moments, which can not be explained by considering the net density of states. Using a tight-binding coherent potential approximation (CPA) model, we show that while the polarization of the net density of states is not correlated with the magnetic moment, the polarization of the density of states of {\it s} electrons is correlated with the magnetic moment in the same manner as observed by the tunneling experiments. We also discuss the spin polarization measurements by Andreev reflection experiments, some of which obtained different results from the tunneling experiments and our calculations.

cond-mat.mtrl-sci↗