Ultrafast charge-transfer-induced spin transition in cobalt-tungstate molecular photomagnets
Résumé
In materials exhibiting photoinduced phase transitions, and in which both charge transfer and spin transitions occur, there has long been a debate about which process drives the phase transition. Herein, we present experimental evidence supporting an optically charge-transfer-induced spin transition (CTIST) process, as demonstrated through femtosecond optical spectroscopy in two-dimensional cyanido-bridged cobalt-tungstate photomagnets. Optical and magnetic studies revealed that the photoexcitation of the ground low-temperature (LT) CoIIILS-WIV state leads to a photoinduced phase transition towards the CoIIHS-WV state, which is similar to the high temperature (HT) state. Ultrafast spectroscopy further indicates that this optical excitation of the intermetallic W-to-Co charge-transfer band produces a transient photoexcited (PE) CoIILS-WV state, which decays within 130 fs through a spin transition towards the CoIIHS-WV state. Here we show that the CTIST dynamics corresponds to the CoIIILS-WIV (LT) → CoIILS-WV (PE) → CoIIHS-WV (HT) sequence. The present work sheds a new light on understanding optical dynamics underlying the photoinduced phase transitions.
Mots clés
- Photoexcitation
- Tungstate
- Femtosecond
- Phase transition
- Spectroscopy
- Spin transition
- Materials science
- Spin states
- Cobalt
- Ground state
- Ultrafast laser spectroscopy
- Excitation
- Metallurgy
- Quantum mechanics
- Optics
- Laser
- Physics
- Condensed matter physics
- Crystallography
- Atomic physics
- Chemistry
- Chemical physics
Domaines
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