Dipolar interaction effects in the spin-dependent transport in nanoparticle syst

2019-12-12 03:53:55

magnetic particle spin GMR dependent

责任者: Kechrakos, D.;Trohidou, K.N. 单位: Inst. of Mater. Sci., Nat. Center for Sci. Res. Demokritos, Athens, Greece 来源出处: Physica Status Solidi A(Phys. Status Solidi A (Germany)),2002/02/,189(2):277-80 摘要: 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 关键词: giant magnetoresistance;granular materials;magnetic particles;magnetisation;Monte Carlo methods;nanostructured materials;particle size;percolation;spin Hamiltonians;superparamagnetism;tight-binding calculations;dipolar interaction;spin-dependent transport;nanoparticle systems;giant magnetoresistance;GMR;granular metal;blocked clusters;superparamagnetic clusters;magnetic microstructure;Monte Carlo simulation;magnetic configuration;real space Kubo formula;spin-dependent tight binding Hamiltonian;electronic conductivity;magnetization parabola;magnetic grains;particle sizes;percolation threshold;particle coalescence