Molecular Quantum Spintronics

Multifunctional devices

Integrating functional spacers, such as the ferroelectric property of molecules, into spintronic devices is a means of achieving a multifunctional device, i.e. a device whose state (e.g. resistance) depends on a history of external stimuli (electric field, light, temperature, magnetic field, etc…). This targets Information and Communication Technologies.

Energy Harvesting

Our team is developping a new method to harvest the thermal fluctuations of ambient temperature using spintronics. Our devices integrate the paramagnetic centers of oxide and molecular compounds into spintronic devices that also comprise electrodes that select a spin channel for transport. This latter feature is accomplished using so-called spinterfaces (see below). See www.spinengine.tech for more details.

In the news

We published a first quantum theory of a two-cycle quantum spintronic engine that harvests vacuum fluctuation energy and bosonic drive energy in the form of a directed electrical current. Phys. Rev. B 109, 165432 (2024).

We call on atomic electronic physicists to help deepen our understanding of the quantum spintronic engine. npj Quantum Info. 9, 25 (2023).

We’ve reproduced our prior observation of spontaneous electrical power output on nine molecular spintronic devices. This ‘quantum spintronic engine’ utilizes magnetic exchange coupling between phthalocyanine molecules, and its strokes can reach ~100THz. A magnetoresistance of 770% is observed — a record for molecular spintronics. Adv. Mater. 34 2206688 (2022).

We’ve observed the robust reversibility of ferroelectricity in croconic acid molecular films. Nanoscale 13 19466 (2021)

We developed a novel nanotechnological process to study spin-polarized transport across a molecular spin chain within a solid-state device. Electrically exciting the spin chain from its quantum ground state generates a specific magnetoresistance signal. This quantum encoding of information lays the groundwork for information transmission across the spin chain. Adv. Func. Mater. 2009467 (2021).  Savoir Magazine

The website www.spinengine.tech describes the concept to spintronically harvest thermal fluctuations to the academic and general publics.

We reported spontaneous electrical power generation from a single spintronic device at room temperature. In this ‘spin engine’, the thermal fluctuations of paramagnetic centers are spintronically harvested. In the process, we demonstrated that the current flowing across the ‘spinterface’ is highly spin-polarized. Commun. Phys., 2 116 (2019). CNRS News. , Unistra News. , www.spinengine.tech

We factually demonstrated that the spin crossover molecular property is involved in electrical transport, thanks to synchrotron-grade in operando experiments. ACS Appl. Mater. & Int., 10 31580 (2018). Soleil Highlight 2018.

We harnessed the chemical selectivity of synchrotron-grade X-ray absorption spectroscopy to probe the active atoms of a device in operation. Adv. Mater., 1606578 (2017).  CNRS News

We demonstrated how to electrically modulate the magnetism of the ferromagnet/molecule interface, aka the ‘spinterface’. Adv. Func. Mater., 1700259 (2017). Soleil Highlight 2017.

We reported the simplest method to achieve a highly spin-polarized current source: create an interface between a ferromagnet and carbon atoms. Carbon 87, 269 (2015). CNRS News.

The ‘spinterface’

The interface between a ferromagnet a molecule can develop emergent properties that are nicknamed the ‘spinterface’. The spinterface exhibits a low density of highly localized and highly spin-polarized electronic states at the Fermi level.  We recently demonstrated that the current flowing across the spinterface is highly spin-polarized at room temperature. Thanks to these properties, the spinterface constitutes an essential building block to address the quantum spin states of other nano-objects within our spintronic devices.

Molecular spin chains

The formation of the spinterface can modify the electronic properties of the metal and molecule constituents. A ferromagnetic metal may see its magnetic anisotropy radically altered. A non-magnetic metal can become magnetic. The magnetization of the molecular interfacial layer can be extended into the molecular film by harnessing magnetic interactions between molecules. This allows the spinterface to stabilize the magnetization of paramagnetic spin chains borne by molecules. Here, we use planar phthalocyanine molecules with a central paramagnetic site. We are studying how to spintronically address the ground and excited states of these spin chains using molecular nanojunctions. These molecules are also used to study the spintronic harvesting of thermal fluctuations.

Spin crossover molecules

The central magnetic site of a spin crossover molecule can be switched from a low-spin to a high-spin electronic configuration using external stimuli (light, temperature, electric field…). This makes it a promising candidate to control a spintronic device’s performance. We demonstrated that this molecular functionality is factually involved in transport using a synchrotron-based operando experiment. The next step is to integrate this molecular class into spintronic nanojunctions. To do so, we are leveraging fundamental research (here and here) on achieving spinterfaces with a noble metal surface so as to not freeze the spin crossover molecular property.

Ferroelectric molecules

Since spin-polarized charge transfer underscores the formation of the spinterface, one may modify the spinterface properties using ferroelectric molecules. To increase this effect, our team is optimizing the structural properties of the spinterface using croconic acid molecules, and intends to integrate these spinterfaces within spintronic nanojunctions. This method of forming an artificial magnetoelectric resembles efforts in the correlated oxides community, but benefits from a large charge transfer that is localized at the interface, and obviates the need to consider the role of oxygen vacancy migration.

Oxygen vacancies & paramagnetic centers

Controlling oxygen vacancies in functional oxides toward next-generation electronics remains challenging. Our team is examining how oxygen vacancies in the ‘simple’ oxide MgO drive the spintronic performance of magnetic tunnel junctions. Our experimental and theoretical results indicate that single and double oxygen vacancies can explain the combination of high spintronic performance, low barrier heights and metallic conduction depending on the junction’s magnetic state. We are examining the impact of these nano-objects on spin-transfer torque, a linchpin physical effect for spintronic technologies. Filling these vacancies with C can promote paramagnetic centers, leading to spintronic energy harvesting.

Team Members

Mebarek ALOUANI

Professor, Magnetic Objects on the NanoScale (DMONS)Mebarek.Alouani@ipcms.unistra.fr

Phone: +33(0)3 88 10 70 06Office: 0008

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Samy BOUKARI

Assistant professor, Magnetic Objects on the NanoScale (DMONS)Samy.Boukari@ipcms.unistra.fr

Phone: +33(0)3 88 10 71 75Office: 1007

Martin BOWEN

Senior Researcher, Magnetic Objects on the NanoScale (DMONS)Martin.Bowen@ipcms.unistra.fr

Phone: +33(0)3 88 10 70 92Office: 0011

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Benoît GOBAUT

Research Engineer, Magnetic Objects on the NanoScale (DMONS)Benoit.Gobaut@ipcms.unistra.fr

Phone: +33(0)3 88 10 70 92Office: 0011

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Loic JOLY

Research Engineer, Magnetic Objects on the NanoScale (DMONS)Loic.Joly@ipcms.unistra.fr

Phone: +33(0)3 88 10 72 57Office: 1008

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Christophe KIEBER

Engineer, Magnetic Objects on the NanoScale (DMONS)Christophe.Kieber@ipcms.unistra.fr

Phone: +33(0)3 88 10 67 82Office: 0023

Mathieu LAMBLIN

PhD student, Magnetic Objects on the NanoScale (DMONS)mathieu.lamblin@ipcms.unistra.fr

Phone: +33(0)3 88 10 70 84Office: 1017

Wolfgang WEBER

Professor, Magnetic Objects on the NanoScale (DMONS)Wolfgang.Weber@ipcms.unistra.fr

Phone: +33(0)3 88 10 70 87, +33(0)3 88 10 70 02Office: 1048

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Prior Members

Eric Beaurepaire, décédé en Avril 2018.
Jacek Arabski, retraite en 2020.