7 Tesla SQUID Magnetometer (NSF DMR-0113714) The Result of the Month (December 2002) Magnetic properties of S = 2 material MnCl3(C12H8N2) * E. Cizmar1, J.-H. Park1, M. W. Meisel1, B.-H. Ward2, D. R. Talham2 1Department of Physics, University of Florida 2 Department of Chemistry, University of Florida

2.0x10-4 0.15

35 30 MnCl (phen) -4 3 ]

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] 1.0x10 C 10 20K G ] 0.05 u u 5

m 30K m -5 0 e e [ 0 4 8 12 16 20 24 28 [

5.0x10 no bg substracted y n t

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t b i a t 0.0 z p i t e c e s n -0.05 u -5 g S -5.0x10 a M ZFC -4 -0.10 -1.0x10 FC 100G no bg substracted -1.5x10-4 -0.15 0 10 20 30 40 50 -8 -6 -4 -2 0 2 4 6 8 Temperature [K] Magnetic field [T] Fig. 1. Magnetic susceptibility of the field-cooled Fig. 2. Field dependence of magnetization of the (100 G) and zero field-cooled sample MnCl3(C12H8N2) polycrystalline sample at temperatures 5, 10, 20 and measured in temperature range from 2 K to 50 K with 30 K. H = 100 G. Inset: temperature dependence of the heat capacity of pelleted sample.

The material MnCl3(C12H8N2), identified as an S = 2 antiferromagnetic linear chain is closely related to the S = 2 Haldane system MnCl3(C10H8N2) [1]. Replacing the C10H8N2 group by C12H8N2 led to the dramatic change of magnetic properties of the system. A difference between the zero-field cooled (ZFC) and field-cooled (FC) magnetization response below 22 K has been observed in our measurements carried out on polycrystalline sample (see Fig. 1), while the specific heat studies revealed magnetic ordering at 2.75 K. The results of ac susceptibility measurements are inconsistent with the presence of a potential spin-glass transition at 22 K. In addition, the field dependence of magnetization of the sample has been measured at temperatures 5, 10, 20 and 30 K (see Fig. 2), with no saturation observed up to 7 T. Additional support provided by the NSF through INT-0089140 and DGE-0209410. [1] G.E. Granroth et al., Phys. Rev. Lett. 77 (1996) 1616. * This work is part of a larger set of measurements that will be reported at the International Conference on Magnetism (ICM 2003), to be held in Rome in July-August 2003, and involves additional coauthors S.J. Gamble, J. van Tol, L.-C. Brunel, M. Orendáč, A. Feher, and J. Šebek. Questions or Suggestions, e-mail me [email protected].