Ultrafast charge-transfer-induced spin transition in cobalt-tungstate molecular photomagnets

Abstract 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 t...

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Main Authors: Kazuki Nakamura, Laurent Guérin, Gaël Privault, Koji Nakabayashi, Marius Hervé, Eric Collet, Shin-ichi Ohkoshi
Format: Article
Language:English
Published: Nature Portfolio 2025-06-01
Series:Nature Communications
Online Access:https://doi.org/10.1038/s41467-025-60401-4
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Summary:Abstract 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) CoIII LS-WIV state leads to a photoinduced phase transition towards the CoII HS-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) CoII LS-WV state, which decays within 130 fs through a spin transition towards the CoII HS-WV state. Here we show that the CTIST dynamics corresponds to the CoIII LS-WIV (LT) → CoII LS-WV (PE) → CoII HS-WV (HT) sequence. The present work sheds a new light on understanding optical dynamics underlying the photoinduced phase transitions.
ISSN:2041-1723