Ferromagnetism and spin transitions in prussian blue: a solid-state hybrid functional study

Middlemiss, D. S. and Wilson, C. C. (2008) Ferromagnetism and spin transitions in prussian blue: a solid-state hybrid functional study. Physical Review B, 77(15), p. 155129. (doi: 10.1103/PhysRevB.77.155129)

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Publisher's URL: http://dx.doi.org/10.1103/PhysRevB.77.155129


The exchange interactions underlying the weak ferromagnetism of the prototypical mixed valence compound prussian blue (represented by K+Fe3+ [Fe2+ (CN)6]) and a Cr3+ substituted analog are investigated within a series of solid-state hybrid density functional calculations. Weights of Hartree–Fock (HF) exchange in the range from 30% to 100% are used. The magnetic order in these compounds is shown to be dominated by the coupling of nearest-neighbor high spin (HS) Fe3+-Fe3+ and Cr3+-Cr3+pairs, and not by the delocalization of spin along the ⋯NCFe2+CN⋯pathways as previously proposed. The functional containing 35% HF exchange yields an estimated critical temperature for spin ordering and a magnitude for weak Fe2+ spin polarization in good agreement with experimental data. The energies of the Fe2+ low spin (LS)→HS (t62g→t42ge2g) and Fe3+ HS→LS (t32ge2g→t52g) excitations are determined and compared with the results obtained previously in a range of Fe2+ coordination compounds. It is concluded that the accurate description of these transitions requires the use of a weight of HF exchange below the stable limit of 35% attained in the current study. However, the trends in the present results indicate that the Fe3+ HS→LS excitation is lower in energy than the Fe2+ LS→HS, and also that there is no reasonable prospect of a temperature-induced spin crossover in either compound.

Item Type:Articles
Keywords:Accurate, analogs, cation, chemistry, coordination, correlation, energies, cr-iii cyanides, crossover, delocalization, density, functional calculations, energies, energy exchange, exchange, interactions, excitation, hf, hybrid, magnets, mixed-valence, neutron-diffraction, pathway, solid-state, spin temperature, transition, transitions, valence, valence delocalization, weak, weak ferromagnetism
Glasgow Author(s) Enlighten ID:Wilson, Professor Charles and Middlemiss, Dr Derek
Authors: Middlemiss, D. S., and Wilson, C. C.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Physical Review B
Publisher:American Physical Society
ISSN (Online):1550-235X
Published Online:29 April 2008

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
372601A scalable mosaic array for ultrasonic imagingDavid CummingEngineering & Physical Sciences Research Council (EPSRC)GR/T19803/01Electronic and Nanoscale Engineering
380771Engineering and understanding solid state proton migration and transferCharles WilsonEngineering & Physical Sciences Research Council (EPSRC)GR/T21615/01CHEM - CHEMISTRY