Voltage-Tunable Magnetic Stability in a Ni Nanoparticle

We study single nickel particles $\approx 2$nm in diameter using single electron tunneling spectroscopy and find that such particles lie at the threshold of stable ferromagnetic order. We find that the application of a bias voltage can precisely tune the conditions for a stable magnetization orientation, and simulate the experimental configuration using a master equation. Due to the addition of anisotropy from a single electron, a new energy scale emerges which governs the stability of magnetization as a function of voltage bias conditions.