Relaxation dynamics in a Fe7nanomagnet

Abstract

We investigate the phonon-induced relaxation dynamics in the Fe${}_{7}$ magnetic molecule, which is made of two Fe${}^{3+}$ triangles bridged together by a central Fe${}^{3+}$ ion. The competition between different antiferromagnetic exchange interactions leads to a low-spin ground state multiplet with a complex pattern of low-lying excited levels. We theoretically investigate the decay of the time correlation function of molecular observables, such as the cluster magnetization, due to the spin-phonon interaction. We find that more than one time contributes to the decay of the molecular magnetization. The relaxation dynamics is probed by measurements of the nuclear spin-lattice relaxation rate $1/{T}_{1}$. The interpretation of these measurements allows the determination of the magnetoelastic coupling strength and to set the scale factor of the relaxation dynamics time scales. In our theoretical interpretation of $1/{T}_{1}$ data we also take into account the wipeout effect at low temperatures.