Magnetic Anisotropy of Cyanide‐Bridged Core and Core–Shell Coordination Nanoparticles Probed by X‐ray Magnetic Circular Dichroism. Issue 21 (20th March 2013)

• Record Type: Journal Article
• Authors: Prado, Yoann; Arrio, Marie‐Anne; Volatron, Florence; Otero, Edwige; Cartier dit Moulin, Christophe; Sainctavit, Philippe; Catala, Laure; Mallah, Talal
• Is Part Of: Chemistry. Volume 19:Issue 21(2013)
• Page Start: 6685
• Page End: 6694
• Publication Date: 2013-03-20
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201203609
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The local symmetry and local magnetic properties of 6 nm‐sized, bimetallic, cyanide‐bridged CsNiCr(CN)<sub>6</sub> coordination nanoparticles <bold>1</bold> and 8 nm‐sized, trimetallic, CsNiCr(CN)<sub>6</sub>@CsCoCr(CN)<sub>6</sub> core–shell nanoparticles <bold>2</bold> were studied by X‐ray absorption spectroscopy (XAS) and X‐ray magnetic circular dichroism (XMCD). The measurements were performed at the Ni<sup>II</sup>, Co<sup>II</sup>, and Cr<sup>III</sup> L<sub>2, 3</sub> edges. This study revealed the presence of distorted Ni<sup>II</sup> sites located on the particle surface of <bold>1</bold> that account for the uniaxial magnetic anisotropy observed by SQUID measurements. For the core–shell particles, a combination of the exchange anisotropy between the core and the shell and the pronounced anisotropy of the Co<sup>II</sup> ions is the origin of the large increase in coercive field from 120 to 890 Oe on going from <bold>1</bold> to <bold>2</bold>. In addition, XMCD allows the relative orientation of the magnetic moments throughout the core–shell particles to be determined. While for the bimetallic particles of <bold>1</bold>, alignment of the magnetic moments of Cr<sup>III</sup> ions with those of Ni<sup>II</sup> ions leads to uniform magnetization, in the core–shell particles <bold>2</bold> the magnetic moments of the isotropic Cr<sup>III</sup> follow those of Co<sup>II</sup> ions in the shell and those of Ni<sup>II</sup> ions in the core, and this leads to nonuniform magnetization in the whole nanoobject, mainly due to the large difference in local anisotropy between the Co<sup>II</sup> ions belonging to the surface and the Ni<sup>II</sup> ions in the core.</p> </abstract>