Eur. Phys. J. B 14, 115-124 (2000)
https://doi.org/10.1007/s100510050112

Photo-excitation from dia- to ferri-magnetism in a Rb-Co-hexacyanoferrate Prussian blue analogue

¹ Laboratoire de Magnétisme et d'Optique, CNRS-Université de VersaillesUnité Mixte 8634, 45 avenue des États-Unis, 78035 Versailles Cedex, France
² Laboratoire de Chimie Inorganique et Matériaux Moléculaires, CNRS-Université Pierre et Marie CurieUnité Associée 7071, 4 place Jussieu, 75252 Paris Cedex 05, France

Received: 12 March 1999
Revised: 11 December 1999
Published online: 15 March 2000

Abstract

We studied the photo-excitation process, the relaxation of the photo-excited state towards the stable state, and the photo-induced magnetic properties of the Prussian blue analogue Rb_0.52Co [Fe(CN)₆]_0.84, 2.3 H₂O. Magnetic, Mössbauer and reflectivity measurements have been performed during and after illumination. The efficiency of the photo-excitation device is maximum at nm. The process, however, is severely hindered by bulk absorption of the light; it is rapidly completed at the surface of the sample and then proceeds slowly in the bulk. Under the effect of photo-excitation the system turns from a dia- to a ferri- magnet, with a value K, indicative of the transformation of the material due to the following optical electron transfer: Thermal relaxation towards the stable electronic state is observed in the 95-110 K temperature interval, obeying a self-accelerated kinetics. At low temperature, a weak, non-exponential, relaxation is detected. These features are discussed in terms of co-operative effects in the frontal process of photo- excitation. The peculiarities of a photo-excited state created below the magnetic ordering temperature are discussed. A metastable magnetic state has been observed in low fields, denoted "Raw Photo-Induced State" (RPI), with a magnetization curve in-between the field-cooled and zero-field-cooled curves.