Enhancement of the Magnetic Ordering Temperature and Air Stability of a Mixed Valent Vanadium Hexacyanochromate(III) Magnet to 99 °C (372 K)

Abstract

The observation of ferro-and ferrimagnetic ordering at relatively high and even ambient temperatures has been established for several hexacyanometalate-based materials possessing the Prussian blue structure type.[1] High Curie (critical) temperature (T c ) magnets may find applications in many areas, including magnetic shielding and memory storage devices. [2] Examples of these materials with high ) reported for (1).[1e] The n CN of (4) and ( [5b] were not detected from IR studies. Upon brief exposure of (4) and (5) as powders to air, as reported for (2) and (3), [1h,i] V=O forms within the lattice, resulting in the appearance of the n V=O (978 cm ±1 for (4), and 974 cm ±1 for (5)) band as well as a shift of the strong n CN absorption to 2170 cm ±1 for (4) and 2174 cm ±1 for (5). Nonetheless, it retains its magnetic behavior. The powder X-ray diffraction patterns of (4) and (5) are nearly featureless, so the materials are essentially amorphous. This was also observed for (1)[1e] and it is assumed that the local structure (cubic) and unit cell parameter (a = 10.66 ) determined by extended X-ray absorption fine structure (EXAFS) for (1) [1e] are similar in (4) and (5). The measured density of (4), 1.652(5) Mg m ±3 , is in good agreement with the calculated density of 1.636 Mg m ±3 based on the above unit cell parameter (a = 10.66 ) and the composition as determined below. Based upon the observed density the calculated a is 10.62 . In contrast, the measured density of (5) The compositions of (4) and (5) were analyzed by X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometry (EDS), and thermogravimetric analysis (TGA). The results of the XPS studies were used to determine the stoichiometry of elements and the mixed oxidation states of the vanadium ions. An average formula of K 0.50 V

Poly[[hexa-μ-cyanido-manganese(II)iron(III)] pentahydrate]

“…Data collection: PROCESS-AUTO (Rigaku, 1998); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku, 2007) Curie temperatures (T C ) (Ferlay et al, 1995;Holmes & Girolami, 1999;Hatlevik et al, 1999;Ohkoshi et al, 2000), humidity-response , photomagnetism (Ohkoshi & Hashimoto, 2001;Sato et al, 1996;Ohkoshi et al,1997), and zero thermal expansion (Margadonna et al, 2004 (Ludi et al, 1970;Ludi & Güdel, 1973;Güdel et al, 1973) and et al, 1992;Zeigler et al, 1999;Kato et al, 2003), where M A and M B are transition metal ions and A is an alkali metal ion. Recently, rubidium manganese hexacyanoferrate, Rb x Mn[Fe(CN) 6 ] (x + 2)/3 .zH 2 O, has received attention due to its various functionalities such as a charge-transfer phase transition (Tokoro et al, 2004;Ohkoshi et al, 2005), a pressureinduced magnetic pole inversion (Egan et al, 2006), and a photomagnetic effect .…”

“…For general background on Prussian blue compounds, see . For related literature, see: Egan et al (2006); Ferlay et al (1995); Gü del et al (1973); Gadet et al (1992); Hatlevik et al (1999); Holmes & Girolami (1999); Ludi et al (1970); Margadonna et al (2004); Ohkoshi & Hashimoto (2001); Ohkoshi et al (1997Ohkoshi et al ( , 2000Ohkoshi et al ( , 2004Ohkoshi et al ( , 2005; Sato et al (1996); Tokoro et al (2003Tokoro et al ( , 2004; Zeigler et al (1999).…”

Metal Substitution Effect on a Three-Dimensional Cyanido-Bridged Fe Spin-Crossover Network

“…In the field of molecule-based magnets [26][27][28][29][30], cyanido-bridged metal assemblies have drawn attention because they exhibit various magnetic functionalities such as a high Curie temperature (T c ) [31][32][33][34], a charge transfer transition [35][36][37][38][39][40][41][42], and an externally stimulated phase transition phenomena [43][44][45][46][47]. In the recent years, we have synthesized several kinds of magnetic cyanido-bridged bimetal assemblies possessing Fe spin-crossover sites.…”

Two binuclear cyanide-bridged Cr(III)-Mn(III) complexes based-on [Cr(2,2’-bipy)(CN)4]- building block: synthesis, crystal structures and magnetic properties

“…Furthermore, based-on the symmetry of the magnetic orbitals from the magnetic point of view, it is possible to predict the nature of the magnetic exchange between the cyanide-bridged paramagnetic metal ions by using simple orbital models. Therefore, up to now, a large amount of cyanide-bridged magnetic complexes with divers structures from 0D cluster to 3D network and interesting magnetic properties, such as highest T C molecule-based materials, moleculebased photomagnets, spin crossover materials, single-molecule magnets (SMMs), and single-chain magnets (SCMs), [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] have been successfully synthesized, structurally characterized and magnetically investigated.…”