Master Thesis
Sara Sales Merino, student in the degree of Physics (UAB) is developing an internship (JAE INTRO) under supervision of Gervasi Herranz on the project of manybody theory of strongly correlated systems.
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Sara Sales Merino, student in the degree of Physics (UAB) is developing an internship (JAE INTRO) under supervision of Gervasi Herranz on the project of manybody theory of strongly correlated systems.
Written by Palma Scarcia on . Posted in FEATURED, News.
ISrTiO3-based conducting interfaces, which exhibit coexistence of gate-tunable 2D superconductivity and strong Rashba spin-orbit coupling (RSOC), are candidates to host topological superconductive phases. Yet, superconductivity is usually in the dirty limit, which tends to suppress nonconventional pairing and therefore challenges these expectations. Here we report on LaAlO3/SrTiO3 (LAO/STO) interfaces with large mobility and mean free paths comparable to the superconducting coherence length, approaching the clean limit for superconductivity. We further show that the carrier density, mobility, and formation of the superconducting condensate are controlled by the fine-tuning of La/Al chemical ratio in the LAO film. We find a region in the superconducting phase diagram where the critical temperature is not suppressed below the Lifshitz transition, at odds with previous experimental investigations. These findings point out the relevance of achieving a clean-limit regime to enhance the observation of unconventional pairing mechanisms in these systems.
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Janine Gücklehorn delivers a talk at APS March Meeting 2025 (Anaheim, California). The title of the talk is “Effect of dielectric polarizability on Rashba spin-orbit coupling in Al/Sr1-xCaxTiO3 interfaces” in the Session MAR-W52 “Emerging Trends in Perovskite Oxides: Structure, Properties, and Applications”
Friday March 21 10:00 am
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E. Longo et al. Giant Spin-Charge Conversion in Ultrathin Films of the MnPtSb Half-Heusler Compound. Advanced Functional Materials 2407968 (2024)
DOI: https://doi.org/10.1002/adfm.202407968
Abstract:
Half-metallic half-Heusler compounds with strong spin-orbit-coupling and broken inversion symmetry in their crystal structure are promising materials for generating and absorbing spin-currents, thus enabling the electric manipulation of magnetization in energy-efficient spintronic devices. In this work, we report the spin-to-charge conversion in the sputtered half-Heusler MnPtSb within thickness (t) range from 1 to 6 nm. A combination of X-ray and transmission electron microscopy measurements evidence the epitaxial nature of these ultrathin non-centrosymmetric layers, with a clear (111)-orientation on top of (0001) single-crystal sapphire. By broadband ferromagnetic resonance (FMR), we observe a four orders of magnitude tunable spin accumulation in the MnPtSb-based heterostructures, within t=1-6 nm range. By using spin pumping FMR, we measure a remarkable t-dependent spin-charge conversion in the MnPtSb layers, which clearly demonstrates the interfacial origin of the conversion. When interpreted within the inverse Edelstein effect (IEE), the spin-charge conversion efficiency extracted at room temperature for the thinnest MnPtSb layer reaches λIEE~3 nm, representing an extremely high conversion at room temperature. The still never explored ultrathin regime of the MnPtSb films studied in this work and the discovery of their outstanding functionality are two ingredients which demonstrate the potentiality of such materials for future applications in spintronics.
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Dr. Gyanendra Singh has delivered the talk “Signature of unconventional superconductivity in 2D oxide interfaces” in the symposium T1.01 Unconventional superconductivity and magnetism in SCES VI at the International Conference on Magnetism 2024, held in Bologna, Italy.
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Dr. Jaume Gazquez has delivered the talk “Large photoresponse, strain and grain boundaries of LaFeO3-based heterojunctions” in the Workshop Advanced Electron Microscopy For Advanced Materials, held in Wuzhen, China.
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Prof. Kyle Shen, from the Department of Physics at Cornell University, deliveres a talk at ICMAB entitled “Thin Film Nickelates: A New Frontier for High-Temperature Superconductivity”.
Here the abstract about the talk:
Superconductivity plays a key role in many next-generation technologies, including quantum computing and sensing. The promise of discovering new superconductors with higher transition temperatures has been at the forefront of research in condensed matter physics, materials science, and solid state chemistry for the past 4 decades. From the high-temperature cuprate superconductors of the 1990s, to the iron-based superconductors of the 2010s, significant attention has now been directed in the past few years to the nickelate families of superconductors, particularly the so-called “infinite layer” nickelates as well as the recently discovered bilayer nickelate, La3Ni2O7.
In this seminar, I will describe recent advances in the study of the infinite-layer and bilayer nickelate superconductors. I will highlight new thin film synthesis approaches developed by our research group, and how this enables investigations of superconductivity and the phase diagram of both these families.
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Dr. Emanuele Longo has delivered the talk “Possible orbital momentum accumulation in the SrVO3 light early transition metal oxide” in the Symposium T3.03 Spin-orbit effects and spin-charge-orbit conversion phenomena II at the International Conference on Magnetism 2024, held in Bologna, Italy.
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MULFOX’ PhD Student Mario Villa contributed with two oral presentations entitled “Large photoresponse and grain boundaries of LaFeO3-based heterojunctions” and “Microstructural domain mapping of LaFeO3-based heterojunctions” within the Advanced PV material characterization and Analytical techniques for accurate nanoscale characterization of advanced materials symposiums respectively during the EMRS Spring meeting held in Strasbourg, France during May, 2024.
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Pol Salles, Roger Guzman, Huan Tan, Martí Ramis, Ignasi Fina, Pamela Machado, Florencio Sánchez, Gabriele De Luca, Wu Zhou, and Mariona Coll
ACS Appl. Mater. Interfaces 2024 (2024)
DOI: https://doi.org/10.1021/acsami.4c05013
The ability to prepare single crystalline complex oxide freestanding membranes has opened a new playground to access new phases and functionalities not available when they are epitaxially bound to the substrates. The water-soluble Sr3Al2O6 (SAO) sacrificial layer approach has proven to be one of the most promising pathways to prepare a wide variety of single crystalline complex oxide membranes, typically by high vacuum deposition techniques. Here, we present solution processing, also named chemical solution deposition (CSD), as a cost-effective alternative deposition technique to prepare freestanding membranes identifying the main processing challenges and how to overcome them. In particular, we compare three different strategies based on interface and cation engineering to prepare CSD (00l)-oriented BiFeO3 (BFO) membranes. First, BFO is deposited directly on SAO but forms a nanocomposite of Sr–Al–O rich nanoparticles embedded in an epitaxial BFO matrix because the Sr–O bonds react with the solvents of the BFO precursor solution. Second, the incorporation of a pulsed laser deposited La0.7Sr0.3MnO3 (LSMO) buffer layer on SAO prior to the BFO deposition prevents the massive interface reaction and subsequent formation of a nanocomposite but migration of cations from the upper layers to SAO occurs, making the sacrificial layer insoluble in water and withholding the membrane release. Finally, in the third scenario, a combination of LSMO with a more robust sacrificial layer composition, SrCa2Al2O6 (SC2AO), offers an ideal building block to obtain (001)-oriented BFO/LSMO bilayer membranes with a high-quality interface that can be successfully transferred to both flexible and rigid host substrates. Ferroelectric fingerprints are identified in the BFO film prior and after membrane release. These results show the feasibility to use CSD as alternative deposition technique to prepare single crystalline complex oxide membranes widening the range of available phases and functionalities for next-generation electronic devices.
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We are pleased to announce that Gyanendra Singh and Gervasi Herranz will be delivering invited talks at the 7th International Workshop on Complex Oxides in Cargèse, Corsica. Gyanendra Singh will discuss “Stoichiometric Control of 2D Superconductivity and Mobility at SrTiO3-Based Interfaces,” while Gervasi Herranz will present on “Spin-Orbit Entanglement Driven by the Jahn-Teller Effect.” Join us for these insightful sessions on groundbreaking research in complex oxides!
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The School was held on 30 and 31 May 2024, and had a participation of 150 attendants, among them 36 in-person and 114 online.
The school included a seminar on “Signatures of a spin-orbital chiral metal” by Mario Cuoco on 29th May. It was followed by lectures on 30th and 31th May by Annika Johansson, Andrea Caviglia and Mario Cuoco, which motivated lively discussions, comments and suggested intriguing prospectives.

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Karla Mena, Martí Ramis, Mariona Coll and former member of the team Pol Sallés participated at the EMRS Spring meeting held in Strasburg May 2024
Karla Mena presented an oral contribution on multiferroic composites for energy harvesting, Martí Ramis presented a poster on nanomechanical properties of manganite membranes on plastic substrates, Mariona Coll delivered an invited talk on the opportunities of chemical methods to prepare freestanding complex oxide membranes and Pol Sallés presented an invited talk on the challenges to prepare BiFeO3 membranes by chemical solution deposition.
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Dr. Takayuki Shiino and Dr. Weronika Janus joined MULFOX as postdoctoral researchers, and Teodor Apetrei joined as a Ph.D. candidate. We warmly welcome them to the group and wish them success.
Takayuki received his BSc in Physics (2013) and MSc in Materials Science and Engineering (2016) from Tokyo Institute of Technology (Japan) and KAIST (South Korea), respectively. He received his Ph.D. from Nagoya University (Japan) in 2019 with a thesis on a quantum critical phenomenon in heavy-fermion materials. After the PhD, he experienced two postdoctoral researches: Uppsala University (2019 – 2021, Sweden) and KAIST (2022 – 2024, South Korea) for the studies of quasicrystals and spintronics, respectively. His postdoctoral research at MULFOX focuses on spintronic devices with insulating ferrimagnetic materials.
Weronika studied at AGH University of Krakow, Poland, where she obtained her BSc in Biomedical Engineering (2018), MSc in Biomedical Engineering – Bionanotechnology (2019), and PhD in Physics (2014). During her PhD, she focused on the strain manipulation of magnetic properties in antiferromagnetic thin films. Her current research interest is in developing innovative magnetic insulator-based spintronic memory devices, where the information can be written and read by all-electrical means
Teodor obtained his BSc. degree in Computational Physics at University Alexandru Ioan Cuza Iasi (Romania, 2020) and his MSc. degree in Applied and Engineering Physics at Technische Universitat Munchen (Germany, 2023). The main focus of his current research is the growth and engineering of magnetic oxide and nitride thin films by magnetron sputtering with tunable interfacial chiral magnetism and perpendicular anisotropy.
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This is the 3rd Edition of “ICMAB Schools on Frontiers in Materials Science and Condensed Matter”. Previous editions were “Angle Resolved Photoemission Spectroscopy (https://arpes2023.icmab.es/)” and “Orbital currents in solids (https://orbitalcurrents2023.icmab.es/)”
More information at https://topologicalinterfaces2024.icmab.es/
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Emanuele Longo delivers a talk at the CIC nanoGune Institute in Donostia-San Sebastian the 14th March 2024 with title “Ferromagnetic resonance experiments on SrVO3 thin films: Evidence of orbital currents?” hosted by Prof Felix Casanova.
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Gervasi Herranz delivers a talk (IN-PERSON MEETING) on 6th March at 2:18 PM at the APS March Meeting 2024 (Minneapolis, Minnesota, USA) in Session N04: Ordering Phenomena in Spin-Orbit Coupled Systems
Room: L100D The talk is N04.00011 : Electromagnetic detection of spin-orbit entangled states in Jahn-Teller Mn3+ ions”.
Gyanendra Singh delivers a talk (VIRTUAL MEETING) on 6th March at 12:30 PM the APS March Meeting 2024 (Minneapolis, Minnesota, USA) Abstract: HH05.00006 : Stoichiometric control of 2D superconductivity and mobility at SrTiO3-based interfaces.
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C. T. Parzyck, N. K. Gupta, Y. Wu, V. Anil, L. Bhatt, M. Bouliane, R. Gong, B. Z. Gregory, A. Luo, R. Sutarto, F. He, Y.-D. Chuang, T. Zhou, G. Herranz, L. F. Kourkoutis, A. Singer, D. G. Schlom, D. G. Hawthorn & K. M. Shen
Nat. Mater. (2024)
DOI: https://doi.org/10.1038/s41563-024-01797-0
A hallmark of many unconventional superconductors is the presence of many-body interactions that give rise to broken-symmetry states intertwined with superconductivity. Recent resonant soft X-ray scattering experiments report commensurate 3a0 charge density wave order in infinite-layer nickelates, which has important implications regarding the universal interplay between charge order and superconductivity in both cuprates and nickelates. Here we present X-ray scattering and spectroscopy measurements on a series of NdNiO2+x samples, which reveal that the signatures of charge density wave order are absent in fully reduced, single-phase NdNiO2. The 3a0 superlattice peak instead originates from a partially reduced impurity phase where excess apical oxygens form ordered rows with three-unit-cell periodicity. The absence of any observable charge density wave order in NdNiO2 highlights a crucial difference between the phase diagrams of cuprate and nickelate superconductors.
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M. Gamino, A. B. Oliveira, D. S. Maior, P. R. T. Ribeiro, F. L. A. Machado, T. J. A. Mori, M. A. Correa, F. Bohn, R. L. Rodríguez-Suárez, J. Fontcuberta, and S. M. Rezende
Phys. Rev. B 2023, 108, 224402;
DOI: https://doi.org/10.1103/PhysRevB.108.224402
We report on processes of generation of spin current and conversion into charge current in CoFe2O4/Pt bilayers by means of spin Hall magnetoresistance (SMR) and spin Seebeck effect (SSE) experiments. Specifically, we explore (001) full-textured CoFe2O4 (CFO) thin films grown onto (001)-oriented SrTiO3 substrates, covered with Pt layers deposited under two different conditions: one at room temperature and another at high temperature (400∘C). The x-ray absorption spectroscopy measurements indicate that the Pt layer deposited at high temperature induces an interfacial magneticlike phase (Fe,Co)-Pt alloy, which influences the magnetic behavior of the structure and is responsible for the enhancement of the spin transmission at the interface. By analyzing the SMR data, we conclude that collinear and noncollinear magnetic domains coexist at the CFO-(Fe,Co)-Pt interface. By combining the data from the SMR and SSE measurements, we obtain the ratios between the values of the spin Hall angle (θSH) and between the ones of the spin-mixing conductance (g↑↓eff) in the two samples. We demonstrate that while the value of θSH decreases by one-half with the heat treatment, the value of g↑↓eff increases by more than one order of magnitude. We interpret the increase of g↑↓eff in terms of unexpected magnetic reconstructions, which produce an enhancement of the magnetic moment arisen at the interface. Since the spin-mixing conductance determines the efficiency of the spin current transmission through the interface, the spinel ferrite cobalt in contact with a normal metal with a suitable heat treatment becomes a promising material for spintronics device applications.
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The ICMAB organized Orbital Currents School 2023 conclued.
With a participation of about 70 attendants in-person and 110 on line, the School has finished. A very exciting Introductory lecture by Tatiana G. Rappoport, was followed by lectures by Aurélien Manchon, Dongwook Go, Enric Canadell, Hyun-Woo Lee and Can Onur Avci, which motivated living discussions, comments and suggested intriguing prospectives.


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Yoann Lechaux, Yu Chen; Albert Minj, Florencio Sánchez, Gervasi Herranz, Laurence Méchin, Bruno Guillet
In this work, we study the electronic properties of defects in the LaAlO3/SrTiO3 heterostructure, which is known to host a high mobility two-dimensional electron gas (2DEG) at the interface. This 2DEG also shows photoconductance, which could be related to defects that act as deep center trapping and releasing carriers by interaction with light. This phenomenon has raised an interest for the identification of deep energy levels in the LaAlO3/SrTiO3 heterostructure. We have studied the defect state properties using electrical characterization such as capacitance–voltage (C–V), current–voltage (I–V) measurements, and deep-level transient Fourier spectroscopy (DLTFS). From C–V and I–V analyses, a hysteresis was observed indicating an effect of mobile charges in the LaAlO3. Using DLTFS, we identify three defect states located at around 0.17 eV below conduction band and at 0.23 and 0.26 eV above the valence band. These defect states were attributed to defects in SrTiO3 such as strontium vacancies or titanium vacancies. We identify a fourth defect state having an energy of about 0.69 eV below the conduction band that could be related to oxygen vacancies in LaAlO3 or in SrTiO3. In addition, the observation of an effect of the electric field with DLTFS indicated that oxygen vacancies might be involved in Fowler–Nordheim or trap-assisted tunneling through the LaAlO3 layer.
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Rafael Trócoli, Carlos Frontera, Judith Oró-Solé, Clemens Ritter, Pere Alemany, Enric Canadell, M. Rosa Palacín, Josep Fontcuberta, and Amparo Fuertes
Chem. Mater. 2022, 34, 13, 6098–6107 (2022); DOI:doi.org/10.1021/acs.chemmater.2c01240
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E. Demirci, J. de Rojas, A. Quintana, I. Fina, E. Menéndez, and J. Sort
Appl. Phys. Lett. 121, 081904 (2022); DOI:doi.org/10.1063/5.0091231
These results stem from strain-mediated magnetoelectric coupling. The applied electric field causes changes in the coercivity and the squareness ratio of the films, suggesting a reorientation of the effective magnetic easy axis in Fe80Ga20. However, larger HEB values are observed when the squareness ratio is lower. It is claimed that the effect of voltage is equivalent to an in-plane component of an applied magnetic field oriented perpendicular to the cooling field direction. Perpendicular in-plane magnetic fields have been shown to induce an increase in exchange bias in some ferromagnetic/antiferromagnetic systems due to partial recovery of the untrained antiferromagnetic state. Remarkably, here, this effect is directly induced with voltage, therefore enhancing energy efficiency.
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G. Singh, G. Venditti, G. Saiz, G. Herranz, F. Sánchez, A. Jouan, C. Feuillet-Palma, J. Lesueur, M. Grilli, S. Caprara, and N. Bergeal
Phys. Rev. B 105, 064512 (2022); DOI:doi.org/10.1103/PhysRevB.105.064512
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Xiao Long, Huan Tan, Saúl Estandía, Jaume Gazquez, Florencio Sánchez, Ignasi Fina and Josep Fontcuberta
APL Materials 10, 031114 (2022); DOI:doi.org/10.1063/5.0076865
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Tingfeng Song, Florencio Sánchez, and Ignasi Fina
APL Materials 10, 031108 (2022); DOI:doi.org/10.1063/5.0083661
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Tingfeng Song, Huan Tan, Saúl Estandía, Jaume Gàzquez, Martí Gich, Nico Dix, Ignasi Fina and Florencio Sánchez
Nanoscale, 2022,14, 2337-2343 (2022); DOI:10.1039/D1NR06983G