Spin frustration in M{sup II}[C(CN){sub 3}]{sub 2} (M = V, Cr). A magnetism and neutron diffraction
Three-dimensional coordination network solids of M{sup II}[C(CN){sub 3}]{sub 2} (M = V, Cr) composition possess interpenetrating rutile-like network structures. Each [C(CN){sub 3}]{sup {minus}} bonds to three different metal ions in a triangular array, affording a geometrical topology akin to a Kagome lattice leading to competing spin exchange interactions and spin frustration. The crystal and magnetic structure of Cr{sup II}[C(CN){sub 3}] was determined by Rietveld refinement of the powder neutron diffraction data at 2 and 15 K and belongs to the orthorhombic space group Pmna [a = 7.313(1) {angstrom}, b = 5.453(1) {angstrom}, c = 10.640(1) {angstrom}, Z = 2, T = 15 K]. Each Cr{sup II} has a tetragonally elongated octahedral structure with four Cr-N(1) distances of 2.077(2) {angstrom} and two significantly longer axial Cr-N(2) distances of 2.452(2) {angstrom}. Magnetic susceptibility measurements between 1.7 and 300 K reveal strong antiferromagnetic interactions for both V- and Cr[C(CN){sub 3}]{sub 2} with {theta} = {minus}67 and {minus}46 K, respectively, from a fit to the Curie-Weiss law. Long-range magnetic ordering does not occur for M = V above 1.7 K, in contrast to M = Cr, which antiferromagnetically orders at low temperature. This is attributed to Jahn-Teller distorted Cr{sup II} sites relieving frustration in one dimension, leading to 2-D Ising antiferromagnetism, as observed by both magnetic susceptibility and specific heat studies. Neutron diffraction experiments at 2 K for Cr[C(CN){sub 3}]{sub 2} yielded additional Bragg reflections as a result of antiferromagnetic ordering with the moments on the Cr{sup II} atoms aligned parallel to c and 4.7(1) {micro}{sub B}. Fitting of the magnetic order parameter to a power law yielded T{sub N} = 6.12(4) K and {beta} = 0.18(1) consistent with 2-D Ising behavior. A T{sub N} of 6.13 K is also observed from the specific heat data.
- Research Organization:
- Univ. of Utah, Salt Lake City, UT (US)
- Sponsoring Organization:
- American Chemical Society; USDOE
- DOE Contract Number:
- FG03-93ER45504
- OSTI ID:
- 20023358
- Journal Information:
- Inorganic Chemistry, Vol. 39, Issue 6; Other Information: PBD: 20 Mar 2000; ISSN 0020-1669
- Country of Publication:
- United States
- Language:
- English
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