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Light driven phonomagnetism

Categoria
Seminario
Data
2019-11-22 10:00 - 11:30
Luogo
14 - 15 IV piano St. 9
Affiliation
Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
Area di Ricerca
Superconduttivita', Sistemi fortemente correlati, Eterostrutture e loro applicazioni

The ability to encode spin information with minimal energy dissipation is of great scientific and technological interest. In materials that exhibit simultaneously electric and magnetic order, controlling spins via strain and electric fields becomes viable, providing an energy-efficient route towards ultimate information recording speed. Recently, selective excitation of elementary vibrations of the crystal lattice (phonons) by ultrashort pulses of light has emerged as a novel low-energy route to control material properties, extending strain engineering to the ultrafast timescales. Although pioneering experiments have demonstrated that driving optical phonons can affect magnetism by launching coherent spin precession, no switching of the spin orientation and light-induced magnetic symmetry breaking has been shown so far. Ultrafast magnetic switching is a thriving field but its main focus until now has been the excitation of spin precession via electronic absorption. Here we investigate light-induced magnetism in dysprosium orthoferrite (DyFeO_3), a material with multiple electric and magnetic orders and a strong interaction between spins and the crystal lattice. We show that a sub-ps pulse of an intense THz electric field, tuned to resonance with a specific vibrational mode of the crystal lattice, drives a coherent spin-reorientation within a half-cycle of the spin precession, developing long-living weak ferromagnetic order. Light-driven phonon displacements promptly lower the energy barrier separating competing magnetic states. Magnetic switching occurs via a sudden reconfiguration of the energy landscape, a non-thermal route significantly faster than heat driven phase transformations.

 
 

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