Abstract
The spin exchange interactions of VO(CH3CO2)2 and VO(OCH2CH2O) were investigated by performing spin dimer analysis based on tight binding calculations and mapping analysis based on first principles density functional theory calculations. In agreement with experiment, both analyses show that the magnetic properties of VO(CH3CO2)2 and VO(OCH2CH2O) are best described by uniform antiferromagnetic one-dimensional chain and isolated antiferromagnetic dimer models, respectively. Our study shows that the nearest-neighbor spin exchange in the one-dimensional chains of VO5 square pyramids in VO(CH3CO2)2 is mediated by the C 2pπ orbital of the carboxylate group, and that the cis spin dimers of VO(OCH2CH2O) provide strong antiferromagnetic spin exchange than do the trans spin dimers of VO(OCH2CH2O).
Graphical abstract
The spin exchange interactions in VO(CH3CO2)2 is mediated by the C 2pp orbital of the carboxylate group.
Keywords: Spin exchange interaction; Spin dimer analysis; DFT calculations; Vanadyl acetate; Vanadyl glycolate
Article Outline
Fig. 1. (a) Perspective view of the crystal structure of VO(CH3CO2)2, where the blue, red, cyan and white circles represent V, O, C and H atoms, respectively, the black cylinders represent the equatorial V–Obs bonds of VO5 square pyramid. (b) Perspective view of the crystal structure of VO(OCH2CH2O), where the blue, red, cyan and white circles represent V, O, C and H atoms, respectively, and the black cylinders represent the equatorial V–Obs bonds of VO5 square pyramid (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. Ordered spin arrangements (a) FM and (b) AF of VO(CH3CO2)2, where the gray and white circles refer to the up and down spin sites of V atoms, respectively.
Fig. 4. Ordered spin arrangements (a) FM, (b) AF1 and (c) AF2 of VO(OCH2CH2O), where the gray and white circles refer to the up and down spin sites of V atoms, respectively. The numbers 1 and 2 represent the spin exchange paths Jcis and Jtrans, respectively.
Fig. 5. Magnetic orbitals ψ+ and ψ− of the spin dimer (VO)2(O2CCH3)6 representing the spin exchange Jnn of VO(CH3CO2)2.
Fig. 6. Magnetic orbitals ψ+ and ψ− of the cis spin dimer (VO)2(OCH2CH2O)4 representing the spin exchange Jcis of (VO)(OCH2CH2O).
Fig. 7. Magnetic orbitals ψ+ and ψ− of the trans spin dimer (VO)2(OCH2CH2O)4 representing the spin exchange Jtrans of (VO)(OCH2CH2O).
Fig. 8. Schematic representations of the idealized (a) cis-V2O8 spin dimer and (b) trans-V2O8 spin dimer, where θ represents the dihedral angle between the basal planes of the two edge-sharing VO5 square pyramids.
Table 1.
Calculated and experimental spin exchange parameters J (in kBK) of VO(CH3CO2)2 and VO(OCH2CH2O.
a Taken from Ref. [1].
b Taken from Ref. [2].
Table 2.
(Δe)2 values in (meV)2 calculated for the spin dimers of (VO)(CH3CO2)2 and of (VO)(OCH2CH2O).
Table 3.
Values of the VV distance in Å and (Δe)2 in (meV)2 calculated for the idealized cis-V2O8 and trans-V2O8 spin dimers as a function of the dihedral angle θ between the basal planes of the two edge-sharing VO5 square pyramids.a
a The experimental dihedral angles for the cis- and trans-V2O8 dimers are 141.4° and 175.6°, respectively.
Solid State Sciences Volume 12, Issue 5, May 2010, Pages 685-690 International Symposium on Structure-Property Relationships in Solid-State Materials |