Magnetic Prussian Blue Analogs

Girolami, Gregory S.

doi:10.1002/3527604383.ch9

Cited by 103 publications

(141 citation statements)

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“…The estimated positive coefficient ∆T C /∆p = 29 K/GPa is the highest positive change of T C with pressure which has so far been published for any PBA. From the Hückel calculations [2] follows that the antiferromagnetic contribution to the coupling J is given approximately by the expression 2S(∆ 2 − δ 2 ) 1/2 , where δ is the energy gap between (unmixed) a and b orbitals, ∆ is the energy gap between the molecular orbitals built from them, and S is the monoelectronic overlap integral between a and b. The applied pressure reduces the length of exchange path Cr 2+ −N ≡ C−Cr III and increases overlap integral S. The applied pressure can increase ∆ leading to an increase in both terms (∆ − δ), (∆ + δ) and this way leads to strengthening of the antiferromagnetic coupling.…”

Section: Resultsmentioning

confidence: 99%

“…Magnetic properties of PBA can be analyzed within two simplifications: (i) only the super-exchange interaction between the nearest neighbor metal A 2+ and B III (A 2+ −N ≡ C−B III ) ions have to be considered; (ii) if the magnetic orbital symmetries of the metal ions are the same, the super-exchange interaction is antiferromagnetic (J AF ); conversely, when their magnetic orbital symmetries are different, the super-exchange interaction is ferromagnetic (J F ) [1][2][3]. The B III ion, surrounded by the carbon atoms of six cyanide ligands, experiences a large ligand field.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Pressure on Magnetic Properties of Hexacyanochromates

et al. 2008

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We present the study of pressure effect on magnetic properties of TM 2+ 3 [Cr III (CN) 6 ] 2 · nH 2 O ferrimagnets and ferromagnets (TM = Cr and Co) under pressures up to 0.9 GPa. Applied pressure strengthens super--exchange interaction in Cr 2+ -prussian blue analogues with dominant antiferromagnetic interaction JAF leading to increase in the Curie temperature TC (∆T c /∆p = 29.0 K/GPa) and reduces T C of Co 2+ -prussian blue analogues with dominant ferromagnetic interaction JF (∆Tc/∆p = −1.8 K/GPa). The rise of J AF interaction is attributed to the enhanced value of the single electron overlapping integral S. On the other hand, the applied pressure slightly affects bonding angles between magnetic ions mediated by the cyano-bridge and reduces the strength of magnetic coupling. Changes of the magnetization curve with pressure can be attributed to changes of magnetic anisotropy. The reduction of magnetization with pressure observed on Cr 2+ -prussian blue analogues can be explained by pressure induced transition from Cr 2+ high spin state to Cr 2+ low spin state. All pressure induced changes are reversible.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Pressure on Magnetic Properties of Hexacyanochromates

et al. 2008

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“…These electronic and spin configurations are consistent with the literature. 35) The electronic structure of the transition metal cyanides is characterized by the broad CN and CN Ã bands and several sharp 3d bands located in between. In (a) Na 2 Co 2þ Fe 2þ (CN) 6 , for example, the CN and CN Ã bands are observed below À2:5 eV and above 3.0 eV.…”

Section: Comparison With Lda+u Calculationmentioning

confidence: 99%

Electronic Structure of Hole-Doped Transition Metal Cyanides

Kurihara¹,

Funashima²,

Ishida³

et al. 2010

J. Phys. Soc. Jpn.

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Electronic structures of hole-doped transition metal cyanides, Na 0:84Àx Co[Fe(CN) 6 ] 0:71 . 3.8H 2 O (NCF71), Na 0:72Àx Ni[Fe(CN) 6 ] 0:68 . 5.1H 2 O (NNF68) and Na 1:60Àx Co[Fe(CN) 6 ] 0:90 . 2.9H 2 O (NCF90),were investigated by means of the x-ray absorption spectroscopy and the valence differential spectroscopy. The x-ray absorption spectroscopy revealed that the holes are introduced on the Fe, Fe, and Co sites for the NCF71, NNF68 and NCF90 films, respectively. Owning to the valence differential spectroscopy, we unambiguously assigned the spectral components to the respective optical transitions. We further found that an ab initio band calculation based on the local density approximation with the onsite Columbic repulsion (LDA+U) semi-quantitatively explains the optical transitions.

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“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Among those networks are the bimetallic cyanide-bridged Prussian blue analogues (PBA) with face centred cubic structure ( Fm3m ) and general formula A x M y [M′(CN) 6 ] z , where M and M′ are divalent and trivalent metallic ions respectively and A is an alkaline ion. [19][20][21][22][23][24] The fi rst reports on PBA coordination nanoparticles using a bottom-up approach started in 1997 using different chemical processes that required the presence of an agent (organic or inorganic) to stabilize the particles, and thus precluded www.afm-journal.de www.MaterialsViews.com wileyonlinelibrary.combulk of the particles and thus induce relatively large local anisotropy on the surface. [ 40 ] The magneto-crystalline anisotropy of the nanoparticles will then be related to the local anisotropy of Ni II ions.…”

Section: Introductionmentioning

confidence: 99%

Magnetization Reversal in CsNi^IICr^III(CN)₆ Coordination Nanoparticles: Unravelling Surface Anisotropy and Dipolar Interaction Effects

Prado

Mazérat

Rivière

et al. 2014

Adv Funct Materials

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5402www.MaterialsViews.com wileyonlinelibrary.com their post-modifi cation. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] We have reported an alternative surfactant-free synthesis that led, by adjusting the physico-chemical para meters, to the formation of stable colloidal aqueous solutions of nanocrystals with a narrow size distribution. [ 25,26 ] This stability originates from the negatively charged surface and has been exploited to set a versatile simple synthetic route for core-multishell heterostructured nanoparticles. [ 17 ] The method is based on a seed-mediated growth in solution of a shell on the as-obtained colloids either using the same PBA coordination network or another one. [ 17,[25][26][27][28][29] It was quite remarkable to observe that the size distribution of the resulting objects was of the order of 10%. Then, knowing that the cell parameter of the PBA networks is about 1 nm, which corresponds to two atomic layers ( Figure 1 ), such a size distribution corresponds to a control during the growth in solution over one monolayer. [ 17 ] The control of the monodispersity and the absence of stabilizing agents in these anionic objects allowed their organization in thin fi lms, [ 30,31 ] their use for surface nanopatterning, [ 32 ] and is essential for the analysis of their magnetic behaviour (see below).In a fi rst communication, [ 27 ] we have reported a series of cubic-like coordination nanoparticles of the ferromagnetic network CsNi II Cr III (CN) 6 ( T C (bulk) = 90 K) with sizes ranging from 6 to 30 nm and a narrow distribution (10-20%), using the seedmediated growth process. The study of the magnetic properties of these particles dispersed in a polymer (polyvinylpyrrolidone, PVP, for instance) allowed us determining experimentally the single domain limit size that was found to be around 15-16 nm. Below this size, as expected, a uniform reversal of the magnetization was observed. These results were in line with a Néel-Brown thermal activated magnetization reversal process with a relaxation governed by an anisotropy energy proportional to the volume of the particles, with no detectable surface anisotropy effect. [33][34][35] However, upon decreasing their size surface effects may become dominant and contribute greatly to the magnetic anisotropy of nanoparticles. [ 36,37 ] As evidenced in thin fi lms and nanoparticles, surface anisotropy constant is found higher by many orders of magnitude than that of the bulk. [ 1,38,39 ] Specifi cally in PBA nanoparticles, the role of surface anisotropy cannot be neglected because the coordination sphere of the divalent metal ions (Ni II ions here) present on the surface can be different from those belonging to the

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Magnetic Prussian Blue Analogs

Cited by 103 publications

References 157 publications

Effect of Pressure on Magnetic Properties of Hexacyanochromates

Effect of Pressure on Magnetic Properties of Hexacyanochromates

Electronic Structure of Hole-Doped Transition Metal Cyanides

Magnetization Reversal in CsNi^IICr^III(CN)₆ Coordination Nanoparticles: Unravelling Surface Anisotropy and Dipolar Interaction Effects

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Magnetic Prussian Blue Analogs

Cited by 103 publications

References 157 publications

Effect of Pressure on Magnetic Properties of Hexacyanochromates

Effect of Pressure on Magnetic Properties of Hexacyanochromates

Electronic Structure of Hole-Doped Transition Metal Cyanides

Magnetization Reversal in CsNiIICrIII(CN)6 Coordination Nanoparticles: Unravelling Surface Anisotropy and Dipolar Interaction Effects

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Product

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Magnetization Reversal in CsNi^IICr^III(CN)₆ Coordination Nanoparticles: Unravelling Surface Anisotropy and Dipolar Interaction Effects