Dipolar Interaction Effects in the Spin-Dependent Transport in Nanoparticle Systems

✍ Scribed by Kechrakos, D. ;Trohidou, K.N.

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 91 KB
• Volume: 189
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/1521-396x(200202)189:2<277::aid-pssa277>3.0.co;2-4

✦ Synopsis

The relation between the giant magnetoresistance (GMR) of a granular metal containing blocked and superparamagnetic clusters and its underlying magnetic microstructure is studied numerically. A Monte Carlo simulation is implemented to obtain the equilibrium magnetic configuration of the system, and the real space Kubo formula for a spin-dependent tight binding Hamiltonian is used to calculate the electronic conductivity. A flattening of the MR versus magnetization parabola is found at low fields (H % 0) due to the dipolar interactions between the magnetic grains. This effect is enhanced in systems containing a broad distribution of particle sizes. A maximum in the GMR value is found close to the percolation threshold and attributed to particle coalescence. Dipolar effects reduce the maximum GMR value and cause a faster decay with concentration.