Reversed (Negative) Magnetization for Electrochemically Deposited High-Tc Thin Films of Chromium Hexacyanide Magnets

Abstract

Thin films of chromium cyanide Prussian blue-like materials, KnCrx[Cr(CN)6] (ca. 1.0 ± 0.5 μm thick) are electrodeposited on glassy carbon electrodes in amorphous (a) and crystalline (α) forms. The crystalline film shows a X-ray diffraction pattern typical of a face-centered cubic (fcc) Prussian blue-type cubic lattice [a = 10.41(2) A]. The films exhibit quasi-reversible cyclic voltammetric waves, distinct morphologies in SEM images, and strong field-dependent magnetic behavior. The films undergo two one-electron processes, CrII[CrII(CN)6]2- ⇌ CrIII[CrII(CN)6]- + e-, and CrIII[CrII(CN)6]- ⇌ CrIII[CrIII(CN)6] + e-, with some residual CrII being present. The composition is determined from an analysis of the υCN IR data {[CrII(CN)6]4-: υCN = 2072s cm-1; [CrIII(CN)6]3-: υCN = 2185m cm-1} and X-ray photoelectron (XPS) spectral data. The composition of the oxidized and reduced films are CrIII[CrIII(CN)6]0.98[CrII(CN)6]0.02 and K2.0CrII[CrII(CN)6], respectively, for both amorphous and crystalline forms. These ...