Size-dependence of magneto-electronic coupling in Co nanoparticles

Abstract

This paper describes studies of the effect of electron tunneling on magnetic switching in single Co particles large enough to exhibit continuous energy spectra at mK-temperatures. The ground state spin S0, in units of ℏ, is estimated to be ∼104 in these particles. The magnetic switching field decreases versus tunneling current, with the effective magnetic temperature at the switching field smaller by factor of 2–3 compared to that found previously in smaller Co particle where S0∼103. We show that this relatively weak size dependence confirms that the magnetic tunneling transitions in the particle are driven by mesoscopic fluctuations in magnetic anisotropy energy.