Phonon Bottleneck in the Single-Molecule Magnet Fe$_8$ Induced by Pulsed Millimeter-Wave Radiation

ORAL

Abstract

We report measurements of the magnetization dynamics of the Fe$_8 $ single-molecule magnet on timescales as short as $\sim$10 ns using millimeter-wave radiation to drive transitions between the ground ($m$ = 10) and first excited ($m$ = 9) states. We find that during the radiation pulse the magnetization decreases linearly, while afterwards it decays exponentially back to its initial value with a long time constant of $\sim$10 $\mu$s. We interpret these results as evidence of a phonon bottleneck in which a non-equilibrium number of phonons resonant with the 10- to-9 transition builds up in the crystal, leading to an population increase in the m = 9 state. The time for these phonons to decay (either by escaping the crystal or through scattering) is interpreted to be the measured $\sim$10 $\mu$s. We observe that the phonon bottleneck is established in less than $\sim$15 ns, which suggests that the spin-phonon relaxation time $T_1$ is (rather unexpectedly) shorter than this value.

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Authors

  • Mustafa Bal

    • Department of Physics, Amherst College, Amherst, MA 01002

  • Jonathan Friedman

    • Department of Physics, Amherst College, Amherst, MA 01002

  • Wei Chen

    • Physics Department, Stony Brook University, Stony Brook, NY 11794

  • Mark Tuominen

    • Physics Department, University of Massachusetts, Amherst, MA 01003

  • Evan Rumberger

    • Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093

  • David Hendrickson

    • Department of Chemistry and Biochemistry, UCSD
    • Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093
    • University of California at San Diego, Chemistry Dept.