Photoinduced phase transition ofRbMnFe(CN)6studied by x-ray-absorption fine structure spectroscopy

Abstract

Photoinduced magnetic phase transition of $\mathrm{RbMnFe}(\mathrm{CN}{)}_{6}$ has been investigated by means of x-ray-absorption fine structure spectroscopy. Upon visible-light (532 nm) irradiation at 30 K, the material undergoes the photoinduced tautomeric spin transition. Mn and Fe K-edge x-ray-absorption near-edge structure spectra have clarified that upon the phase transition, a Fe $3d$ electron is transferred to the Mn $3d$ level; the electronic state of Mn changes from trivalent ${(d}^{4},$ spin momentum $S=2)$ to divalent ${(d}^{5},S=5/2),$ while the Fe state correspondingly varies from divalent ${(d}^{6},S=0)$ to trivalent ${(d}^{5},S=1/2).$ Local structures have been investigated by the extended x-ray-absorption fine-structure analysis for the photoinduced phase as well as for the low- and high-temperature phases. The low-temperature phase shows a significant Jahn-Teller distortion in the Mn(III) octahedron, where the Mn-N distances for four shorter and two longer bonds are 1.964\ifmmode\pm\else\textpm\fi{}0.008 and 2.21\ifmmode\pm\else\textpm\fi{}0.01 \AA{}, respectively. The high-temperature phase gives a longer Mn-N distance of 2.211\ifmmode\pm\else\textpm\fi{}0.006 \AA{}, although some minor contribution from a shorter distance still remains. It is also revealed that the atomic configuration of the -Fe-C-N-Mn- chain is essentially collinear and that the Rb ions locate at the center of the cubic lattice. The photoinduced phase was found to be structurally and electronically identical to the high-temperature phase.