Magnetic studies of three-dimensional magnets

Background

High critical temperatures, up to room temperature, are achieved in molecule-based magnets, in the case of three-dimensional covalently bonded magnets, such as V(TCNE)x y(solvent) or the "Prussian blue" systems.

Recent Advances

V(TCNE)x y(solvent) [1] is magnetic at room temperature, its extrapolated Tc being about 400 K (125 oC), above its decomposition temperature of 350 K. Although the structure of this material has not been pinned down, we think each TCNE bridges to as many as four different vanadium atoms, each of which is surrounded by up to six ligands, usually nitrogens from different TCNEs. The random anisotropy present in this system leads to magnetic history effects [2,3].

From the same family of compounds with V(TCNE)x y(solvent) are Mn(TCNE)x y(solvent) and Fe(TCNE)2 y(solvent), systems with relatively high Tcs even though they do not reach room temperatures [4,5].

"Prussian blue" systems have a tinkertoy structure with M-CN-M' linkages in 3-D, where M and M' are transition metal ions like V, Cr, Mn, Ni, etc.. Recent studies of such materials showed high temperature magnetism [6].

Publications

J.M. Manriquez, G.T. Yee, R.S. McLean, A.J. Epstein, and J.S. Miller,  A Room Temperature Molecular/Organic-Based Magnet, Science 252, 1415-1417 (1991).

P. Zhou, B. Morin, A.J. Epstein, and J.S. Miller, Magnetization and Static Scaling of High-Tc Random Anisotropy Molecular-Based Disordered Magnet V(tetracyanoethylene)x.y(CH3CN) with x  ~ 1.5 and y  ~ 2, Physical Review B Rapid Communications 48, 1325-1328 (1993).

C.M. Wynn, M.A. Girtu, J. Zhang, J.S. Miller, and A.J. Epstein, Reentrance in the Mn(tetracyanoethylene)x.y(CH2Cl2) high Tc molecule-based ferrimagnet, Physical Review B 58, 8508-8514 (1998).

M.A. Girtu, C.M. Wynn, J. Zhang, J.S. Miller, and  A. J. Epstein, Magnetic properties and critical behavior of Fe(tetracyanoethylene)2 . x(CH2Cl2), a high Tc, molecule-based magnet, Physical Review B 61, 492-500 (2000).

Created by Darren Gebler and Mihai Gîrtu. Maintained by John Rohrbacher. Last updated 6/2/00.