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MA: Magnetismus

MA 11: Molekularer Magnetismus

MA 11.4: Vortrag

Mittwoch, 13. März 2002, 15:15–15:30, H22

Magnetic Hole Burning in Molecular Magnets — •M. Dressel¹, B. Gorshunov¹, K. Rajagopal¹, S. Vontragool¹, and A.A. Mukhin² — ¹1. Physikalisches Institut, Universität Stuttgart — ²General Physics Institute, Russian Academy of Sciences, Moscow

Using a new high frequency ESR method (frequency range 50 GHz to 1.5 THz, external magnetic field up to 8 Tesla), we have studied magnetic excitations and relaxation phenomena in the molecular magnets Mn₁₂ac and Fe₈. We determine the crystal field parameters with unprecedented accuracy and describe the temperature behavior of the transition intensities quantitatively. The influence of the molecular environment is discussed [1]. In Mn₁₂ac, at elevated temperatures “homogeneous” relaxation due to thermal activation dominates the spin dynamics, while for T<2.5 K resonant quantum tunneling becomes important; here “inhomogeneous” relaxation and magnetic hole burning is observed. We have developed a model which allows to quantitatively describe all observed effects and to extract the quantum relaxation parameters, including the effective tunneling splitting and the spin-phonon relaxation rate [2].

[1] A. Mukhin et al., Phys. Rev. B 63, 214 411 (2001)

[2] M. Dressel et al., submitted to Phys. Rev. Lett.