Molecular Magnetocapacitance

TL;DR

This paper demonstrates that in magnetic nanoscale systems, the quantum component of capacitance becomes spin-dependent and can be tuned by an external magnetic field, enabling potential new device functionalities.

Contribution

It introduces the concept of molecular magnetocapacitance, showing that quantum capacitance in magnetic molecules can be controlled via magnetic fields, which is a novel insight.

Findings

First-principles calculations show a 6% difference in capacitance between high-spin and low-spin states.

A magnetic field of ~40T can switch the spin state, altering the capacitance.

Potential for device applications exploiting Coulomb blockade magnetoresistance.

Abstract

Capacitance of a nanoscale system is usually thought of having two contributions, a classical electrostatic contribution and a quantum contribution dependent on the density of states and/or molecular orbitals close to the Fermi energy. In this letter we demonstrate that in molecular nano-magnets and other magnetic nanoscale systems, the quantum part of the capacitance becomes spin-dependent, and is tunable by an external magnetic field. This molecular magnetocapacitance can be realized using single molecule nano-magnets and/or other nano-structures that have antiferromagnetic ground states. As a proof of principle, first-principles calculation of the nano-magnet [Mn3O(sao)3(O2CMe)(H2O)(py)3] shows that the charging energy of the high-spin state is 260 meV lower than that of the low-spin state, yielding a 6% difference in capacitance. A magnetic field of ~40T can switch the spin state, thus changing the molecular capacitance. A smaller switching field may be achieved using nanostructures whose physical properties such as magnetic moment are size-dependent. Molecular magnetocapacitance may lead to revolutionary device designs, e.g., by exploiting the Coulomb blockade magnetoresistance whereby a small change in capacitance can lead to a huge change in resistance.