Molecular spintronics: the role of spin-dependent hybridization

Abstract

Spindependent hybridization at the ferromagnet/molecule interface has recently unveiled a promising new potential for spintronics. By projecting the spintronic properties (i.e. induced spin polarization) from a given ferromagnet electrode to the highly versatile and tailorable molecular layer, spindependent hybridization has opened up new opportunities to tailor spintronic device properties at the molecular scale. Here we focus on the potential and impact of this hybridization on spintronic devices. Depending on the coupling strength at the ferromagnet/molecule interface, the induced spin polarization can be enhanced or even inversed. In the first part of the paper, we introduce the concept of spindependent hybridization and, in particular, we show that it allows the magnetoresistive response of spintronic devices to be tuned. In the second part, we review the experimental evidence emphasizing spindependent hybridization in molecular layers and single molecules. In the last part, we highlight how this spindependent hybridization can play a key role in tunnelling magnetoresistance and tunnelling anisotropic magnetoresistance.

Spin-driven electrical power generation at room temperature

“…We discuss strategies to achieve routine device reproduction. Our work also confirms the high transport spin polarization at room temperature of the ferromagnetic metal/ molecule interface 13 inferred from spectroscopy measurements 14 . Figure 1a illustrates our spin engine in the simplified case of a PM center, characterized by two effectively spin-split energy levels.…”

“…To obtain RT electrical generation, and in the process demonstrate it to be a RT spintronic selector, we utilize the spinterface 13,14,25,26 . This refers to a low energy bandwidth, low density of highly spin-polarized states that arise at room temperature from spin-polarized hybridization between the highly degenerate electronic states of a FM metal such as Co and the few, energetically discrete states of molecules, including carbon atoms 26 .…”

“…1 A room-temperature spin engine. a Illustration of asymmetries in the spin-induced transmission rates Γ across a single paramagnetic (PM) center between spintronic selectors L and R. Spinterfaces 13,14,25,26 , halfmetals 15,17 , Fe/MgO MTJs 20,22 , and ferromagnetic tunnel barriers 19 can fulfill the role of a spintronic selector. b Spin-conserved quantum tunneling between a spinterface and a PM center deforms the PM center's Bloch sphere, thereby splitting 27,28 its spin states by Δ, and shifts the spinterface's Fermi level (E F ) by Δϕ.…”

“…To achieve a strongly spin-dependent transmission rate Γ, the PM center is placed between spintronic selectors-materials systems that ideally favor only one transport spin channel while blocking the other. Examples include half metals [15][16][17] , 2D materials with half-metallic properties 18 , a normal metal / ferromagnetic tunnel barrier 19 bilayer, and the ferromagnetic metal/molecule interface 13 , also called a 'spinterface'. The Fe/MgO system may also constitute a spintronic selector given either a sufficient MgO thickness 20 and/or the presence of oxygen vacancies [21][22][23][24] .…”

Reversible coordination-induced spin-state switching in complexes on metal surfaces

“…Molecular spin switches are attractive candidates for controlling the spin polarization developing at the interface between molecules and magnetic metal surfaces 1,2 , which is relevant for molecular spintronics devices [3][4][5] . However, intrinsic spin switches such as spin-crossover complexes so far suffer from fragmentation or loss of functionality upon adsorption on metal surfaces with rare exceptions [6][7][8][9] .…”