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تسجيل مستخدم جديدQuantum Hole Digging in Magnetic Molecular Clusters
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Below 360 mK, Fe8 magnetic molecular clusters are in the pure quantum relaxation regime. We showed recently that the predicted ``square-root time relaxation is obeyed, allowing us to develop a new method for watching the evolution of the distribution of molecular spin states in the sample. We measured the distribution P(H) of molecules which are in resonance at the applied field H. Tunnelling initially causes rapid transitions of molecules, thereby ``digging a hole in P(H). For small initial magnetisation values, the hole width shows an intrinsic broadening which may be due to nuclear spins. We present here hole digging measurements in the thermal activated regime which may allow to study the effect of spin-phonon coupling.
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The nuclear spin-mediated quantum relaxation of ensembles of tunneling magnetic molecules causes a hole to appear in the distribution of internal fields in the system. The form of this hole, and its time evolution, are studied using Monte Carlo simul
ations. It is shown that the line-shape of the tunneling hole in a weakly polarised sample must have a Lorentzian lineshape- the short-time half-width $xi_o$ in all experiments done so far should be $sim E_0$, the half-width of the nuclear spin multiplet. After a time $tau_o$, the single molecule tunneling relaxation time, the hole width begins to increase rapidly. In initially polarised samples the disintegration of resonant tunneling surfaces is found to be very fast.
Reply to the Comment of J.J. Alonso and J.F. Fernandez on the paper Hole-digging in ensembles of tunneling molecular magnets of I.S. Tupitsyn, P.C.E. Stamp and N.V. Prokofev (Phys. Rev. B 69, 132406, (2004)).
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