Magnetic ordering in an (Fe 0.2 Cr 0.8 ) 1.5 [Cr(CN) 6 ] Prussian blue analogue studied with synchrotron radiation based spectroscopies

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2018, Vol.6 (30), p.8171-8186
• Main Authors: Luque, Francisco Jesús, Kowalik, Iwona Agnieszka, Prieto-Ruiz, Juan Pablo, Niño, Miguel Ángel, Prima-García, Helena, Romero, Francisco Manuel, Arvanitis, Dimitri, Coronado, Eugenio, Miranda, Rodolfo, de Miguel, Juan José
• Format: Article
• Language: English
• Subjects: Cations; Chromium; Curie temperature; Dichroism; Electron spin; Ferromagnetism; Iron; Magnetic moments; Magnetic properties; Oxidation; Pigments; Synchrotron radiation
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/C8TC02879F

The appearance of magnetic order in the (Fe 0.2 Cr 0.8 ) 1.5 [Cr(CN) 6 ]·15H 2 O Prussian blue analogue at low temperature has been investigated by means of synchrotron radiation-based X-ray absorption spectroscopy and X-ray magnetic circular dichroism. With the help of ligand field multiplet analysis we have been able to identify the oxidation states of the metallic cations present in the sample and their evolution with temperature. Our experiments reveal that the appearance of ferromagnetic order is triggered by the transformation of Cr III cations to Cr II high-spin caused by a transfer of electrons from the Fe to the Cr resulting in an increase of the magnetic interactions within the (Cr, Cr) sublattice. The misfit strain between the (Fe, Cr) and the (Cr, Cr) moieties that coexist within this ternary material influences the balance of oxidation states and hence the magnetic properties of the metallic ions. Misfit relaxation also plays a role in determining the differences between the surface and the bulk of the material. The measurement of the magnetic moments in those two regions suggests that the surface may have a reduced Curie temperature compared to the bulk.