Spin-dependent tunneling through layered ferromagnetic nanoparticles

Spin-dependent tunneling has been investigated for nanostructured ferromagnetic tunnel junctions, in which an insulating nanostructured film made of layered hard ferromagnetic Co₈₀Pt₂₀ nanoparticles dispersed in an insulating SiO₂ matrix is sandwiched between two soft ferromagnetic electrodes, an Fe/Co₈₀Pt₂₀ as a bottom electrode and a Co₉Fe as a top electrode. The junctions investigated have three tunnel barriers and exhibited tunnel magnetoresistance of 9% at room temperature with a small resistance at a low field. The charging energy of the particles with an average diameter of 7 nm was estimated to be 45 meV from the temperature dependence of the resistance. Coulomb blockade was not observed for the junctions because of the low junction resistance.