Spin Polarization and Magneto-Coulomb Oscillations in Ferromagnetic Single Electron Devices

TL;DR

This study investigates magneto-Coulomb oscillations in ferromagnetic single electron devices, revealing how magnetic fields influence electron repopulation and Fermi energy shifts, with experimental spin polarization measurements aligning with theoretical predictions.

Contribution

It provides new insights into the mechanism of magneto-Coulomb oscillations driven by Zeeman-induced Fermi energy changes in ferromagnetic single electron transistors.

Findings

Repopulation occurs from Ni to Co electrodes with increasing magnetic field.

Oscillation period is proportional to single electron charging energy.

Experimentally measured spin polarizations are negative for Ni and Co, larger for Ni.

Abstract

The magneto-Coulomb oscillation, the single electron repopulation induced by external magnetic field, observed in a ferromagnetic single electron transistor is further examined in various ferromagnetic single electron devices. In case of double- and triple-junction devices made of Ni and Co electrodes, the single electron repopulation always occurs from Ni to Co electrodes with increasing a magnetic field, irrespective of the configurations of the electrodes. The period of the magneto-Coulomb oscillation is proportional to the single electron charging energy. All these features are consistently explained by the mechanism that the Zeeman effect induces changes of the Fermi energy of the ferromagnetic metal having a non-zero spin polarizations. Experimentally determined spin polarizations are negative for both Ni and Co and the magnitude is larger for Ni than Co as expected from band calculations.