Achievement of Organic-Based Magnets and
Discovery of New Phenomena in Magnetism

The first organic-based ferromagnet reported was decamethylferrocenium alternating with TCNE (Tc = 4.8 K).1 The magnetization shows hysteresis as a function of varying the applied magnetic field, with a coercive force reaching as high as 1 kOe at 2 K.

J.S. Miller, J.C. Calabrese, A.J. Epstein, R.W. Bigelow, J.H. Zhang, and W.M. Reiff, Journal of the Chemical Society, Chemical Communications, 1026 (1986).

S. Chittipeddi, K.R. Cromack, J.S. Miller, and A.J. Epstein, Phsysical Review Letters 58, 2695 (1987).

Subsequent to this 1985 report, Kinoshita et al.2 reported that the nitroxide-based 4-nitrophenyl nitronyl nitroxide, p-NPNN, magnetically orders at Tc = 0.60 K.

M. Takahashi, P. Turek, Y. Nakazawa, M. Tamura, K. Nozawa, D. Shiomi, M. Ishikawa, and M. Kinoshita, Physical Review Letters 67, 746 (1991); erratum, 69, 1290 (1992).

???? Schweizer, Spin density map 1996?

Only one (the phase) of the four different crystal structures of p-NPNN is a ferromagnet.12 Later reports demonstrated nitroxide-based magnets with higher Tc, for example, 1,3,5,7-tetramethyl-2,6-diaza-adamantane-N,N, with a Tc of 1.48 K.3

1,3,5,7-tetramethyl-2.6-diazaadamantane-N,N'-dioxyl; Weak dipolar interaction contributes to low Tc of 1.48 K.
R. Chiarelli, M.A. Novak, A. Rassat, and J.L. Tholence, Nature 363, 147 (1993).

Other organic compounds with a ferromagnetic ground state include [tetrakis(dimethylamino) ethylene][C60] (Tc = 16.1 K),4 while the ß phase of 4’-cyanotetrafluorophenyldithiadiazolyl radical is a weak ferromagnet with Tc of 35.5 K.5 The report6,7 of V[TCNE]x•y(CH2Cl2) having a Tc of ~400 K established room-temperature organic-based magnets as a reality. Subsequently, it was shown that room temperature magnetism was also present in a vanadium/chromium Prussian blue derivative.8–10
In the past 18 years, numerous classes of organic-based ferromagnets, ferrimagnets, and spin glasses have been reported. These materials have magnetic ordering temperatures ranging from <1 K to above room temperature. The range of magnetic behaviors of the three-dimensionally networked M[N(CN)2]2 (M = Co, Ni, Cr, Mn, Cu, Zn) illustrates the important role of both the electronic structure of the organic groups and the occupation of orbitals of metal ions.11–14

We concentrate here on three new phenomena that are unique to organic-based magnets: "high-temperature" lightinduced magnetism,15 spin-polarized magnetic organic semiconductors,16 and the development of fractal magnetic order.17 These three phenomena, together with others, such as spin dilution in a ferromagnetic chain,18 coexistence of glassiness and canted antiferromagnetism (in which the spins involved in the usual "up–down" alternation common in an antiferromagnet are tilted with respect to their neighbor's direction, resulting in a small net magnetic moment) in triangular quantum Heisenberg antiferromagnets,19,20 thermally assisted quantum spin tunneling in single-molecule magnets,21,22 coexistence of an organic-based conductor and molecule-based magnet in the same lattice,23 and the possibilities of spin ladders24 and one-dimensional (1D) magnets,25–27 illustrate the richness of opportunity in organic-based magnets. In some circumstances, hysteresis upon heating and cooling can lead to a substantial change in the magnetic state and magnetic bistability for organic-based materials.28,29

1. J.S. Miller, J.C. Calabrese, A.J. Epstein, R.W. Bigelow, J.H. Zhang, and W.M Reiff, Journal of the Chemical Society, Chemical Communications, 1026 (1986); S. Chittipeddi, K.R. Cromack, J.S. Miller, and A.J. Epstein, Physical Review Letters 58, 2695 (1987).
2. M. Takahashi, P. Turek, Y. Nakazawa, M. Tamura, K. Nozawa, D. Shiomi, M. Ishikawa, and M. Kinoshita, Physical Review Letters 67, 746 (1991); erratum, 69, 1290 (1992).
3. R. Chiarelli, M.A. Novak, A. Rassat, and J.L. Tholence, Nature 363, 147 (1993).
4. P. Allemand, K. Khemani, A. Koch, F. Wudl, K. Holczer, S. Donovan, G. Gruner, and J.D. Thompson, Science 253, 301 (1991).
5. A.J. Banister, N. Bricklebank, I. Lavender, J.M. Rawson, C.I. Gregory, B.K. Tanner, W. Clegg, M.R.J. Elsegood, and F. Palacio, Angewandte Chemie, International Edition 35, 2533 (1996).
6. J.M. Manriquez, G.T. Yee, R.S. McLean, A.J. Eptein, and J.S. Miller, Science 252, 1415 (1991).
7. K.I. Pokhodnya, A.J. Epstein, and J.S. Miller, Advanced Materials 12, 410 (2000).
8. S. Ferlay, T. Mallah, R. Ouahes, P. Veillet, and M. Verdeguer, Nature 378, 701 (1995).
9. O. Hatlevik, W.E. Buschmann, J. Zhang, J.L. Manson, and J.S. Miller, Advanced Materials 11, 914 (1999).
10. S.D. Holmes and G. Girolami, Journal of the American Chemical Society 121, 5593 (1999).
11. C.R. Kmety, J.L. Manson, Q. Huang, J.W. Lynn, R.W. Erwin, J.S. Miller, and A.J. Epstein, Physical Review B 60, 60 (1999).
12. C.R. Kmety, Q. Huang, J.W. Lynn, R.W. Erwin, J.L. Manson, S. McCall, J.E. Crow, K.L. Stevenson, J.S. Miller, and A.J. Epstein, Physical Review B 62, 5576 (2000).
13. J.L. Manson, C.R. Kmety, F. Palacio, A.J. Epstein, and J.S. Miller, Chemistry of Materials 13, 1068 (2001).
14. C.R. Kmety, J.L. Manson, S. McCall, J.E. Crow, K.L. Stevenson, and A.J. Epstein, Journal of Magnetism and Magnetic Materials 248, 52 (2002).
15. D.A. Pejakovic, J.L. Manson, J.S. Miller, and A.J. Epstein, Physical Review Letters 88, 057202 (2002).
16. V.N. Progodin, N.P. Raju, K.I. Pokhodnya, J.S. Miller, and A.J. Epstein, Advanced Materials 14, 1230 (2002).
17. S.J. Etzkorn, W. Hibbs, J.S. Miller, and A.J. Epstein, Physical Review Letters 89, 207201 (2002).
18. K.S. Narayan, B.G. Morin, J.S. Miller, and A.J. Epstein, Physical Review B 46, 6195 (1992).
19. M.A. Girtu, C.M. Wynn, W. Fujita, K. Awaga, and A.J. Epstein, Physical Review B 57, 11058 (1998).
20. M. Girtu, C. Wynn, W. Fujita, K. Awaga, and A.J. Epstein, Physical Review B 61, 4117 (2000).
21. J.R. Friedman, M.P. Sarachik, J. Tejada, and R. Ziolo, Physical Review Letters 76, 3830 (1996).
22. L. Thomas, F. Lionti, R. Ballou, D. Gatteschi, R. Sessoli, and B. Barbara, Nature 383, 145 (1996); S.M.J. Aubin, Z. Sun, L. Pardi, K. Folting, L.-C. Brunel, A.L. Rheingold, G. Christou, and D.N. Hendrickson, Inorganic Chemistry 38, 5329 (1999); A.D. Kent, Y. Zhong, L. Bokacheva, D. Ruiz, D.N. Hendrickson, and M.P. Sarachik, Journal of Applied Physics 87, 5493 (2000).
23. E. Coronado, J.R. Galan-Mascaros, C.J. Gomez-Garcia, and V. Laukhin, Nature 408, 447 (2000).
24. C.P. Landee, M.M. Turnbull, C. Galeriu, J. Giantsidis, and F.M. Woodward, Physical Review B 63, 100402 (2001).
25. R.J. Glauber, Journal of Mathematical Physics 4, 294 (1963).
26. A. Caneschi, D. Gatteschi, N. Lalioti, C. Sangregorio, R. Sessoli, G. Venturi, A. Vindigni, A. Rettori, M.G. Pini, and M.A. Novak, Angewandte Chemie, International Edition 40, 1760 (2001).
27. M. Mito, N. Shindo, T. Tajiri, H. Deguchi, S. Takagi, H. Miyasaka, M. Yamashita, R. Clerac, and C. Coulon, Journal of Magnetism and Magnetic Materials, in press (2003).
28. W. Fujita and K. Awaga, Science 286, 261 (1999).
29. W. Fujita and K. Awaga, Synthetic Metals 137, 1263 (2003).




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