Microwave emission from a crystal of molecular magnets: The role of a resonant cavity

Abstract

We discuss the effects caused by a resonant cavity around a sample of a magnetic molecular crystal (such as Mn12-Ac), when a time dependent external magnetic field is applied parallel to the easy axis of the crystal. We show that the back action of the cavity field on the sample significantly increases the possibility of microwave emission. This radiation process can be supperradiance or a maserlike effect, depending on the strength of the dephasing. Our model provides further insight to the theoretical understanding of the bursts of electromagnetic radiation observed in recent experiments accompanying the resonant quantum tunneling of magnetization. The experimental findings up to now can all be explained as being a maser effect rather than superradiance. The results of our theory scale similarly to the experimental findings, i.e., with increasing sweep rate of the external magnetic field, the emission peaks are shifted towards higher field values.

Magnetic Avalanches in Molecular Magnets

“…Interestingly, Garanin and Chudnovsky have noted that such collective traveling spin reversal fronts are potential sources of Dicke superradiance [41][42][43][44][45][46][47] at frequencies in the teraHertz range, a particularly interesting region of the electromagnetic spectrum where few sources are available. If self-organization does result in a uniform dipolar field within the tunneling front, the resonant condition is fulfilled for a macroscopic number of magnetic molecules inside the front, and it is indeed plausible that these avalanches could emit a superradiant electromagnetic signal.…”

Electromagnetic superradiance from single-molecule magnets in the presence of a classical driving magnetic field

“…The importance of the resonator, as is mentioned in Ref. 28, was emphasized in Ref. 23 and earlier in Ref.…”

“…28 is also very interesting, where the attention therein is focused on the role of a resonator in enhancing the collective radiation when the microwave radiation in the crystal of molecular magnets is considered. The importance of the resonator, as is mentioned in Ref.…”

Dynamics of molecular nanomagnets in time-dependent external magnetic fields: Beyond the Landau-Zener-Stückelberg model

“…In this case the values of the parameters in H 0 are D / k B = 0.56 K, and F / k B = 1.1ϫ 10 −3 K. The coefficients in H 1 do not have unanimously accepted values, but they are essential for the determination of the transition probabilities and can be obtained by fitting the theoretical results to experimental magnetization curves. 13 In this paper we use L = 0.025g B B ͑representing a weak misalignment in the external field B͒, E / k B = −4.48 10 −3 K, C / k B = 1.7ϫ 10 −5 K unless otherwise stated. We note that the main conclusion of this paper is not related to the particular choice of the constants above.…”