Nonequilibrium excitations in Ferromagnetic Nanoparticles

Abstract

In recent measurements of tunneling transport through individual ferromagnetic Co nanograins, Deshmukh, Guéron, Ralph et al. \cite{mandar,gueron} (DGR) observed a tunneling spectrum with discrete resonances, whose spacing was much smaller than what one would expect from naive independent-electron estimates. In a previous publication, \cite{prl_kleff} we had suggested that this was a consequence of nonequilibrium excitations, and had proposed a ``minimal model'' for ferromagnetism in nanograins with a discrete excitation spectrum as a framework for analyzing the experimental data. In the present paper, we provide a detailed analysis of the properties of this model: We delineate which many-body electron states must be considered when constructing the tunneling spectrum, discuss various nonequilibrium scenarios and compare their results with the experimental data of Refs. \cite{mandar,gueron}. We show that a combination of nonequilibrium spin- and single-particle excitations can account for most of the observed features, in particular the abundance of resonances, the resonance spacing and the absence of Zeeman splitting.

13 pages, 10 figures

References in corpus (3)

• Spectroscopy of discrete energy levels in ultrasmall metallic grains
• Magnetic Anisotropy Variations and Non-Equilibrium Tunneling in a Cobalt Nanoparticle
• A Model for Ferromagnetic Nanograins with Discrete Electronic States

Cited by in corpus (9)

• Magnetization orientation dependence of the quasiparticle spectrum and hysteresis in ferromagnetic metal nanoparticles
• Current induced Spin Torque in a nanomagnet
• Elementary Excitations of Ferromagnetic Metal Nanoparticles
• Electron-magnon coupling and nonlinear tunneling transport in magnetic nanoparticles
• Theory of Spin Torque in a nanomagnet
• Anisotropy in Ferromagnetic Nanoparticles: Level-to-Level Fluctuations of a Collective Effect
• Detecting and Switching Magnetization of Stoner Nanograin in Non-local Spin Valve
• Spin fluctuations in quantum dots
• Tunneling density of states in quantum dots with anisotropic exchange