Magnetic Molecules on surfaces: from magnetic bistability towards quantum coherence at the single molecule level

Professor Roberta Sessoli
Department of Chemistry, University of Florence (Italy)
Wednesday 9th March 2016 at 3pm
CQC2T Level 2 Conference Room UNSW

Abstract: Magnetic molecules with magnetic bistability have represented the ideal workbench for the investigation of quantum effects in the magnetization dynamics and are now studied at the single molecule level thanks to scanning probe techniques and synchrotron experiments. Though magnetic hysteresis has been observed on isolated molecules on surface and even enhanced by the interaction with the substrate, cryogenic temperatures are necessary to preserve the magnetic information.

Different is the situation for magnetic molecules carrying a spin center with small magnetic anisotropy and weak spin-orbit coupling, for which long spin coherence times can be observed if the ligand environment is designed to reduce the presence of nuclear spins. Following this synthetic strategy millisecond coherence times have been observed in vanadium(IV) complexes at low temperature. Though not comparable to the coherence time of inorganic structures, magnetic molecules present advantages related to the chemical tunability of their structure. The first challenge to face is that the efficient spin lattice relaxation becomes the limiting factor at high temperature. The vanadyl complexes we have investigated are characterized by long T_1 over a wide range of temperatures and magnetic fields giant spin-phonon bottleneck effects. We have observed room temperature quantum coherence and Rabi oscillations in a vanadyl-titanyl molecular semiconductor that we have evaporated on different substrates with the purpose to embed it in spintronic devices. These evaporable molecules, which preserve their spin moment at the level of monolayer on surfaces, appear as good candidates to investigate quantum coherence at the single molecule level by scanning probe spectroscopies.

Education • 1987: Laurea in Chemistry (110/110 e Lode) at the Università degli Studi di Firenze with a thesis on magnetic properties of low dimensional materials based on nitronyl-nitroxide radicals and transition metal ions
• 1992: PhD in Chemical Sciences at the Università degli Studi di Firenze discussing a thesis on Molecular Magnetic Materials, supervisor Prof. D. Gatteschi

Academic career •1997-2000: Ricercatore SSD CHIM03 presso la Facoltà di Farmacia, Università degli Studi di Firenze
•since 2000: Associate Professor of General and Inorganic Chemistry in the Faculty of Pharamacy, Università degli Studi di Firenze

Main Research Interests. Magnetic Interactions in Inorganic Compounds and Organic Radicals - Electronic Structure of Metal Complexes - EPR Spectroscopy - Low Dimensional Magnetism - Magnetic Molecular Materials - Magnetic Phase Transitions - Spin dynamics in nanostructured materials - Single molecule magnets - Organization and characterization of molecules on surfaces