J. Jeong1, T. M. Briere3, N. Sahoo1,2, T.P. Das1, S. Ohira4, K. Nishiyama3, K. Nagamine3,4
1 Department of Physics, State University of New
York at Albany, Albany, New York, 12222, USA
2 Department of Radiation Oncology, Albany Medical College, Albany, New York, 12208, USA
3 Meson Science Laboratory, High Energy Accelerator Research Organization (KEK), Tsukuba-Shi, Ibaraki, 305, Japan
4 Muon Science Laboratory, Institute for Physical and Chemical Research (RIKEN), Wako Shi, Saitama, 351-01, Japan
Using the Hartree-Fock Cluster procedure , we have studied the trapping of muon (m+) and muonium (Mu) in the chemical ferromagnet p-Chlorobenzene-TEMPO and the muon hyperfine tensors at the trapping sites to evaluate the hyperfine fields expected there. A singlet Mu is trapped near the oxygen site and a triplet Mu is trapped at the bridge nitrogen site. The sites where trapping is found to occur for m+ are adjacent to the chlorine, bridge nitrogen and oxygen sites. However, the calculated hyperfine tensors are too large or too small at all other sites, except the m+ site at the chlorine and the singlet Mu site at oxygen, to explain the two observed mSR frequencies . The direction of the easy axis for the magnetization in the ferromagnetic state is obtained as (010)  by fitting the observed frequencies  using our calculated hyperfine tensors for the m+ trapping site adjacent to chlorine and the singlet Mu trapping site adjacent to oxygen. Comparison will be made with the prediction of the easy axis from dipole-dipole interactions between the magnetic moments on the various molecules in the solid, these magnetic moments being primarily localized for each molecule on the NO group.
 “Electronic Properties of Solids using Cluster Methods” Ed.
T. A. Kaplan and S. D. Mahanti; Plenum Press, New York (1995)
 S. Ohira, Master’s Thesis, University of Tokyo, Japan (1997).
 J. Jeong, et al, Bull. Am. Phy. Soc. 45, No. 1, 1039 (2000)
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