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Marino M, Molteni E, Achilli S, Onida G, Fratesi G. Ab Initio Electronic, Magnetic, and Optical Properties of Fe Phthalocyanine on Cr 2O 3(0001). Molecules 2024; 29:2889. [PMID: 38930954 PMCID: PMC11206909 DOI: 10.3390/molecules29122889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2024] [Revised: 06/14/2024] [Accepted: 06/16/2024] [Indexed: 06/28/2024] Open
Abstract
The organic molecules adsorbed on antiferromagnetic surfaces can produce interesting interface states, characterized by charge transfer mechanisms, hybridization of molecular-substrate orbitals, as well as magnetic couplings. Here, we apply an ab initio approach to study the adsorption of Fe phthalocyanine on stoichiometric Cr2O3(0001). The molecule binds via a bidentate configuration forming bonds between two opposite imide N atoms and two protruding Cr ones, making this preferred over the various possible adsorption structures. In addition to the local modifications at these sites, the electronic structure of the molecule is weakly influenced. The magnetic structure of the surface Cr atoms shows a moderate influence of molecule adsorption, not limited to the atoms in the close proximity of the molecule. Upon optical excitation at the onset, electron density moves toward the molecule, enhancing the ground state charge transfer. We investigate this movement of charge as a mechanism at the base of light-induced modifications of the magnetic structure at the interface.
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Affiliation(s)
- Marco Marino
- ETSF and Physics Department “Aldo Pontremoli”, University of Milan, Via Celoria 16, 20133 Milan, Italy; (E.M.); (S.A.); (G.O.)
| | | | | | | | - Guido Fratesi
- ETSF and Physics Department “Aldo Pontremoli”, University of Milan, Via Celoria 16, 20133 Milan, Italy; (E.M.); (S.A.); (G.O.)
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2
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Gnoli L, Benini M, Del Conte C, Riminucci A, Rakshit RK, Singh M, Sanna S, Yadav R, Lin KW, Mezzi A, Achilli S, Molteni E, Marino M, Fratesi G, Dediu V, Bergenti I. Enhancement of Magnetic Stability in Antiferromagnetic CoO Films by Adsorption of Organic Molecules. ACS APPLIED ELECTRONIC MATERIALS 2024; 6:3138-3146. [PMID: 38828040 PMCID: PMC11137817 DOI: 10.1021/acsaelm.3c01599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 02/14/2024] [Accepted: 02/19/2024] [Indexed: 06/05/2024]
Abstract
Antiferromagnets are a class of magnetic materials of great interest in spintronic devices because of their stability and ultrafast dynamics. When interfaced with an organic molecular layer, antiferromagnetic (AF) films are expected to form a spinterface that can allow fine control of specific AF properties. In this paper, we investigate spinterface effects on CoO, an AF oxide. To access the magnetic state of the antiferromagnet, we couple it to a ferromagnetic Co film via an exchange bias (EB) effect. In this way, the formation of a spinterface is detected through changes induced on the CoO/Co EB system. We demonstrate that C60 and Gaq3 adsorption on CoO shifts its blocking temperature; in turn, an increase in both the EB fields and the coercivities is observed on the EB-coupled Co layer. Ab initio calculations for the CoO/C60 interface indicate that the molecular adsorption is responsible for a charge redistribution on the CoO layer that alters the occupation of the d orbitals of Co atoms and, to a smaller extent, the p orbitals of oxygen. As a result, the AF coupling between Co atoms in the CoO is enhanced. Considering the granular nature of CoO, a larger AF stability upon molecular adsorption is then associated with a larger number of AF grains that are stable upon reversal of the Co layer.
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Affiliation(s)
- Luca Gnoli
- CNR
ISMN, Via Gobetti 101, 40129 Bologna, Italy
| | | | - Corrado Del Conte
- Department
of Physics and Astronomy “A. Righi”, University of Bologna, Via Berti-Pichat 6/2, I-40127 Bologna, Italy
| | | | | | - Manju Singh
- CNR
ISMN, Via Gobetti 101, 40129 Bologna, Italy
| | - Samuele Sanna
- Department
of Physics and Astronomy “A. Righi”, University of Bologna, Via Berti-Pichat 6/2, I-40127 Bologna, Italy
| | - Roshni Yadav
- Materials
Science and Engineering Department, National
Chung Hsing University, Taichung 402, Taiwan
| | - Ko-Wei Lin
- Materials
Science and Engineering Department, National
Chung Hsing University, Taichung 402, Taiwan
| | - Alessio Mezzi
- CNR
ISMN, Via Salaria km
29.300, 00015 Monterotondo
Scalo, Italy
| | - Simona Achilli
- Physics
Department, Università degli Studi
di Milano, Via Celoria 16, 20133 Milan, Italy
| | - Elena Molteni
- Physics
Department, Università degli Studi
di Milano, Via Celoria 16, 20133 Milan, Italy
| | - Marco Marino
- Physics
Department, Università degli Studi
di Milano, Via Celoria 16, 20133 Milan, Italy
| | - Guido Fratesi
- Physics
Department, Università degli Studi
di Milano, Via Celoria 16, 20133 Milan, Italy
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Bergenti I, Kamiya T, Li D, Riminucci A, Graziosi P, MacLaren DA, Rakshit RK, Singh M, Benini M, Tada H, Smogunov A, Dediu VA. Spinterface Effects in Hybrid La 0.7Sr 0.3MnO 3/SrTiO 3/C 60/Co Magnetic Tunnel Junctions. ACS APPLIED ELECTRONIC MATERIALS 2022; 4:4273-4279. [PMID: 36193212 PMCID: PMC9523579 DOI: 10.1021/acsaelm.2c00300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 08/10/2022] [Indexed: 06/16/2023]
Abstract
Orbital hybridization at the Co/C60 interface been has proved to strongly enhance the magnetic anisotropy of the cobalt layer, promoting such hybrid systems as appealing components for sensing and memory devices. Correspondingly, the same hybridization induces substantial variations in the ability of the Co/C60 interface to support spin-polarized currents and can bring out a spin-filtering effect. The knowledge of the effects at both sides allows for a better and more complete understanding of interfacial physics. In this paper we investigate the Co/C60 bilayer in the role of a spin-polarized electrode in the La0.7Sr0.3MnO3/SrTiO3/C60/Co configuration, thus substituting the bare Co electrode in the well-known La0.7Sr0.3MnO3/SrTiO3/Co magnetic tunnel junction. The study revealed that the spin polarization (SP) of the tunneling currents escaping from the Co/C60 electrode is generally negative: i.e., inverted with respect to the expected SP of the Co electrode. The observed sign of the spin polarization was confirmed via DFT calculations by considering the hybridization between cobalt and molecular orbitals.
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Affiliation(s)
- Ilaria Bergenti
- Institute
of Nanostructured Materials ISMN-CNR, Via Gobetti 101, Bologna 40129, Italy
| | - Takeshi Kamiya
- Department
of Materials Engineering Science, Osaka
University, 1-3, Machikaneyama, Toyonaka, Osaka, Japan 560-8531
| | - Dongzhe Li
- CEMES,
Université de Toulouse, CNRS, 29 rue Jeanne Marvig, F-31055 Toulouse, France
| | - Alberto Riminucci
- Institute
of Nanostructured Materials ISMN-CNR, Via Gobetti 101, Bologna 40129, Italy
| | - Patrizio Graziosi
- Institute
of Nanostructured Materials ISMN-CNR, Via Gobetti 101, Bologna 40129, Italy
| | - Donald A. MacLaren
- SUPA,
School of Physics and Astronomy, University
of Glasgow, Glasgow G12 8QQ, U.K.
| | - Rajib K. Rakshit
- CSIR
- National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012, India
| | - Manju Singh
- CSIR
- National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012, India
| | - Mattia Benini
- Institute
of Nanostructured Materials ISMN-CNR, Via Gobetti 101, Bologna 40129, Italy
| | - Hirokazu Tada
- Department
of Materials Engineering Science, Osaka
University, 1-3, Machikaneyama, Toyonaka, Osaka, Japan 560-8531
| | - Alexander Smogunov
- Service de
Physique de l’Etat Condensé (SPEC), CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette
Cedex France
| | - Valentin A. Dediu
- Institute
of Nanostructured Materials ISMN-CNR, Via Gobetti 101, Bologna 40129, Italy
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Picone A, Finazzi M, Duò L, Giannotti D, Ciccacci F, Brambilla A. Observation of a Metastable Honeycomb Arrangement of C 60 on Ni(111) with (7 × 7) Periodicity: Tailoring an Interface for Organic Spintronics. ACS APPLIED NANO MATERIALS 2021; 4:12993-13000. [PMID: 34977478 PMCID: PMC8713361 DOI: 10.1021/acsanm.1c02060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 11/23/2021] [Indexed: 06/14/2023]
Abstract
Hybrid nanostructures in which organic molecules are interfaced with metal surfaces hold promise for the discovery of intriguing physical and chemical phenomena, as well as for the development of innovative devices. In this frame, it is crucial to understand the interplay between the structural details of the interface and the electronic properties of the system. Here, an experimental investigation of the C60/Ni(111) interface is performed by means of scanning tunneling microscopy/spectroscopy (STM/STS) and low-energy electron diffraction (LEED). The deposition of C60 at room temperature, followed by high-temperature annealing, promotes the stabilization of two different phases. A hitherto unreported phase forming a (7 × 7) honeycomb overlayer coexists with the well-known (4 × 4) reconstruction. Highly resolved STM images disclose the adsorption geometry of the molecules for both phases. STS reveals that the electronic properties of C60/Ni(111) are strongly influenced by the morphology of the interface, suggesting the possibility of tuning the electronic properties of the organic/inorganic heterostructures by adjusting the structural coupling with the substrate. This achievement can be important for hybrid magnetic interfaces, where the harmonization between the molecular and the magnetic orders can enhance the development of hybrid magnetic states.
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