Probing Spin Accumulation induced Magnetocapacitance in a Single Electron Transistor

TL;DR

This paper demonstrates that non-equilibrium spin accumulation in a ferromagnetic single-electron transistor induces a significant magnetocapacitance effect, revealing a new way to manipulate charge and spin interactions at the nanoscale.

Contribution

It introduces a novel mechanism where spin accumulation causes tunnel magnetocapacitance, evidenced by asymmetry in Coulomb diamonds in a tunable single-electron transistor.

Findings

Spin accumulation induces tunnel magnetocapacitance up to 40%.

Asymmetry in Coulomb diamonds indicates additional charging energy.

Extra threshold energy is experienced only by electrons entering the island.

Abstract

The interplay between spin and charge in solids is currently among the most discussed topics in condensed matter physics. Such interplay gives rise to magneto-electric coupling, which in the case of solids was named magneto-electric effect, as predicted by Curie on the basis of symmetry considerations. This effect enables the manipulation of magnetization using electrical field or, conversely, the manipulation of electrical polarization by magnetic field. The latter is known as the magnetocapacitance effect. Here, we show that non-equilibrium spin accumulation can induce tunnel magnetocapacitance through the formation of a tiny charge dipole. This dipole can effectively give rise to an additional serial capacitance, which represents an extra charging energy that the tunneling electrons would encounter. In the sequential tunneling regime, this extra energy can be understood as the energy required for a single spin to flip. A ferromagnetic single-electron-transistor with tunable magnetic configuration is utilized to demonstrate the proposed mechanism. It is found that the extra threshold energy is experienced only by electrons entering the islands, bringing about asymmetry in the measured Coulomb diamond. This asymmetry is an unambiguous evidence of spin accumulation induced tunnel magnetocapacitance, and the measured magnetocapacitance value is as high as 40%.