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ESR Intensity and Anisotropy of Nanoscale Molecular Magnet V15

Fa3-4 (LT1175) August 12, 2005, Florida, USA. ESR Intensity and Anisotropy of Nanoscale Molecular Magnet V15. IIS, U. Tokyo, Manabu Machida RIKEN, Toshiaki Iitaka Dept. of Phys., Seiji Miyashita. Nanoscale Molecular Magnet V15. [A. Mueller and J. Doering (1988)]. Vanadiums provide

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ESR Intensity and Anisotropy of Nanoscale Molecular Magnet V15

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  1. Fa3-4 (LT1175) August 12, 2005, Florida, USA ESR Intensity and Anisotropy of Nanoscale Molecular Magnet V15 IIS, U. Tokyo, Manabu Machida RIKEN, Toshiaki Iitaka Dept. of Phys., Seiji Miyashita

  2. Nanoscale Molecular Magnet V15 [A. Mueller and J. Doering (1988)] Vanadiums provide fifteen 1/2 spins. (http://lab-neel.grenoble.cnrs.fr/) Dzyaloshinsky-Moriya (DM) interaction?

  3. Outline of The Talk Part I • A new O(N) algorithm for ESR. • Temperature dependence of ESRintensity. • We reproduce the experimental data. • The effect of DM is not clearly seen. Part II • ESRintensity at very low temperatures. • The intensity is prominently affected by DM. • The deviation due to DM is estimated as

  4. Hamiltonian and Intensity

  5. Difficulty difficult! – Direct diagonalization requires memory of – Its computation time is of (e.g. S. Miyashita et al. (1999))

  6. Our New Method DCEM (The Double Chebyshev Expansion Method) Speed and memory of O(N). Random vector and Chebyshev polynomial. No systematic error. The scheme of time evolution is improved from BWTDM[T. Iitaka and T. Ebisuzaki, PRL (2003)].

  7. DCEM (1) Random phase vector

  8. >> DCEM (2) Chebyshev polynomial expansions of the thermal and time-evolution operators. small w

  9. Comparison with Experiment- Temperature Dependence of - Our calculation Experiment [Y.Ajiro et al. (2003)] SIM(8): Intensity by the lowest eight levels.

  10. With and Without DM

  11. Effect of DM at Low Temperatures Intensity ratio : a 1/2 spin With DM Without DM Calculated by SIM(8) (the lowest eight levels).

  12. Triangle Model and Its Energy Levels Produces energy levels almost equal to those of V15.

  13. Intensity Ratio of Triangle Model up to the first order of D At zero temperature

  14. Summary Temperature dependence of ESR intensity O(N) algorithm both for speed and memory. We reproduce the experimental intensity. Intensity ratio at ultra-cold limit Intensity ratio at weak fields (Mz=1/2) deviates from 1 due to DM interaction. The deviation is given by M. M., T. Iitaka, and S. Miyashita, J. Phys. Soc. Jpn. Suppl. 74 (2005) 107 (cond-mat/0501439). M. M., T. Iitaka, and S. Miyashita, in preparation.

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