Surface scattering dominated magnetotransport for improved quantitative estimation of particle size in Ag100−xCox nanogranular films

The size and distribution of cobalt particles in 100 nm thin films of Ag100−xCox (x=11.8-21.1 at%) co-sputtered at room temperature are determined from the fitting of their room temperature magnetoresistance data by Langevin function using a log-normal particle moment distribution. The systematically combined magnetoresistance and magnetization data indicates the narrow distribution and the progressively interacting nature of the magnetic particles with increase in 'x'. Instead of the conventional magnetization data, the magnetotransport data is proposed for improved quantitative estimation of the particle size owing to their capability to track the surface effects associated with the ultrafine nanoparticles. The particle sizes obtained in the range of 3.9-6.4 nm from this alternate approach are in excellent agreement with those determined from transmission electron microscopy (TEM). On the other hand, the particle sizes determined from the magnetization measurements are systematically larger than determined from TEM. The particle size probing ability of magnetotransport is interpreted by explicitly taking account of the spin-dependent electron scattering within the magnetic particles as well as scattering from the surface of magnetic particle.