Modulating the Ferromagnet/Molecule Spin Hybridization Using an Artificial Magnetoelectric

Abstract

Spin‐polarized charge transfer at the interface between a ferromagnetic (FM) metal and a molecule can lead to ferromagnetic coupling and to a high spin polarization at room temperature. The magnetic properties of these interfaces can not only alter those of the ferromagnet but can also stabilize molecular spin chains with interesting opportunities toward quantum computing. With the aim to enhance an organic spintronic device's functionality, external control over this spin polarization may thus be achieved by altering the ferromagnet/molecule interface's magnetic properties. To do so, the magnetoelectric properties of an underlying ferroelectric/ferromagnetic interface are utilized. Switching the ferroelectric polarization state of a PbZr0.2Ti0.8O3 (PZT) bottom layer within a PZT/Co/FePc‐based (Pc ‐ phthalocyanine) device alters the X‐ray magnetic circular dichroism of the Fe site within the phthalocyanine molecular top layer. Thus, how to electrically alter the magnetic properties of an interface with high spin polarization at room temperature is demonstrated. This expands electrical control over spin‐polarized FM/molecule interfaces, which is first demonstrated using ferroelectric molecules, to all molecular classes.

Encoding Information on the Excited State of a Molecular Spin Chain

“…[ 46 ] To the best of our knowledge, this is the first observation of a specific MR signal that is driven to appear due to bias voltage, and whose amplitude tracks a conductance increase. An electrically driven [ 47,48 ] generation of interfacial MR at a spinterface due to so‐called “magnetic hardening” [ 30,40,43–45 ] past an electric field threshold is not expected to yield a MR term that scales with d I/ d V . Instead, given the above interpretation of d I/ d V , we conclude that MR ES arises from the opening of spin‐flip channels of transport across MSCs.…”

“…Compared to the strategy of electrically altering [ 47,48 ] the charge transfer that generates the spinterface [ 33 ] and interfacial MR, [ 40 ] our strategy of electrically manipulating the quantum states of spin chains away from the spinterface benefits from the ability to electrically control the amplitude/sign of MR using low‐voltage addressing, and to use spin waves to transmit [ 16 ] spin‐encoded information across an organic semiconductor using AF molecular spin chains in a pulsed voltage approach. Electrically controlling the quantum state of a molecular spin chain could help develop antiferromagnetic spintronics [ 17 ] at the quantum level.…”

Disentangling Magnetic Hardening and Molecular Spin Chain Contributions to Exchange Bias in Ferromagnet/Molecule Bilayers

“…This not only constitutes an echo to the milestone from amorphous to ordered inorganic tunnelling spintronics starting in 2001 [29] , but paves the way for solid-state devices studies that exploit the quantum physical properties of spin chains. Here, the recent proposal [15] and experimental demonstration [30] that the organic spinterface can constitute an active component toward multifunctional electronics may be used to electrically alter the molecular spin chain's ground/excited state, so as to craft spin-polarized transport and thus promote novel device functionalities. The magnetism of the resulting interface, also called an organic spinterface, differs from that of its constituent materials.…”

Cu Metal/Mn Phthalocyanine Organic Spinterfaces atop Co with High Spin Polarization at Room Temperature

“…Indeed, the demonstrated robustness of the NM/molecule organic spinterface atop FM suggests that it may also stabilize the correlations in the magnetic fluctuations [19] within a molecular spin chain atop this spinterface. By reducing the magnetic coupling between FM and molecule thanks to the NM spacer, electrical manipulation of the spinterface [33,34] and the spin chain may be more easily distinguished. Furthermore, one can utilize the welldocumented [25] spin transfer torque properties of the FM/NM bilayer to more precisely understand the fundamental interaction between the spin-polarized current and the spin chain's excited states within a solid-state device (e.g.…”