Federico Motti’s research focus on strongly correlated materials, especially magnetic oxides, and engineering their properties in the form of thin films. To understand the underpinning physics, he makes use of synchrotron-based X-ray techniques such as scattering, absorption and photoemission. He is also playing an active role in the development of new instrumentation for photoemission experiments, especially in view of the upgrade of the Elettra synchrotron.
He worked as a PostDoc in the laboratory of Mesoscopic Systems, a joint group of ETH-Zurich/Paul Scherrer Institut (Switzerland), lead by Prof. Laura Heydermann. There he worked with multiferroic thin films and superlattices grown by Pulsed Lased Deposition.
In his PhD at the University of Milan, under the supervision of Prof. Giorgio Rossi, he investigated ferromagnetic/ferroelectric heterostructures and the magneto-electric coupling at their interfaces.
Here, we present an integrated ultra-high vacuum apparatus—named MBE-Cluster —dedicated to the growth and in situ structural, spectroscopic, and magnetic characterization of complex materials. Molecular Beam Epitaxy (MBE) growth of metal oxides, e.g., manganites, and deposition of the patterned metallic layers can be fabricated and in situ characterized by reflection high-energy electron diffraction, low-energy electron diffraction, Auger electron spectroscopy, x-ray photoemission spectroscopy, and azimuthal longitudinal magneto-optic Kerr effect. The temperature can be controlled in the range from 5 K to 580 K, with the possibility of application of magnetic fields H up to ±7 kOe and electric fields E for voltages up to ±500 V. The MBE-Cluster operates for in-house research as well as user facility in combination with the APE beamlines at Sincrotrone-Trieste and the high harmonic generator facility for time-resolved spectroscopy.
Phys. Rev. Materials, 4, 114418, (2020)
Interplay between morphology and magnetoelectric coupling in Fe/PMN-PT multiferroic heterostructures studied by microscopy techniques
F. Motti, G. Vinai, V. Bonanni, V. Polewczyk, P. Mantegazza, T. Forrest, F. Maccherozzi, S. Benedetti, C. Rinaldi, M. Cantoni, D. Cassese, S. Prato, S.S. Dhesi, G. Rossi, G. Panaccione, and P. Torelli
A ferromagnetic (FM) thin film deposited on a substrate of Pb(Mg1/3Nb2/3)O3−PbTiO3 (PMN-PT) is an appealing heterostructure for the electrical control of magnetism, which would enable nonvolatile memories with ultralow-power consumption. Reversible and electrically controlled morphological changes at the surface of PMN-PT suggest that the magnetoelectric effects are more complex than the commonly used “strain-mediated” description. Here we show that changes in substrate morphology intervene in magnetoelectric coupling as a key parameter interplaying with strain. Magnetic-sensitive microscopy techniques are used to study magnetoelectric coupling in Fe/PMN-PT at different length scales, and compare different substrate cuts. The observed rotation of the magnetic anisotropy is connected to the changes in morphology, and mapped in the crack pattern at the mesoscopic scale. Ferroelectric polarization switching induces a magnetic field-free rotation of the magnetic domains at micrometer scale, with a wide distribution of rotation angles. Our results show that the relationship between the rotation of the magnetic easy axis and the rotation of the in-plane component of the electric polarization is not straightforward, as well as the relationship between ferroelectric domains and crack pattern. The understanding and control of this phenomenon is crucial to develop functional devices based on FM/PMN-PT heterostructures.
University of Milan PhD Thesis, (2019)
Strain-mediated magneto electric coupling and beyond: case studies by in-operando spectroscopy
I explored the properties of systems that were fabricated aiming to exploit enhanced multiferroic behavior and potentially useful functionalities at room temperature. The systems of choice for this thesis were two prototypical multiferroic heterostructures composed by a ferromagnetic thin film deposited on a ferroelectric substrate: LSMO/BTO(001) and Fe,FeMn/PMN-PT(001). I focused on the magnetic response of the thin films to applied electric fields oriented perpendicular to the interface, and influencing the substrate. In both the chosen heterostructures the magnetic layers and ferroelectric substrates are all materials with high ordering temperature.
Strada Statale 14 - km 163,5 - 34149 Trieste, ITALY
ph. +39 040 3756487 fax +39 040 226767
NFFA is a Progetto Internazionale financed by MIUR through CNR
(Istituto Officina dei Materiali, Trieste) and Elettra-Sincrotrone Trieste
and managed by the Commissione NFFA chaired by Giorgio Rossi
(Università di Milano and IOM-CNR).