Magnetization and spin dynamics of a Cr-based magnetic cluster : Cr7Ni

We study the magnetization and the spin dynamics of the Cr7 Ni ring-shaped magnetic cluster. Measurements of the magnetization at high pulsed fields and low temperature are compared to calculations and show that the spin Hamiltonian approach provides a good description of the Cr7 Ni magnetic molecule. In addition, the phonon-induced relaxation dynamics of molecular observables has been investigated. By assuming the spin-phonon coupling to take place through the modulation of the local crystal fields, it is possible to evaluate the decay of fluctuations of two generic molecular observables. The nuclear spin-lattice relaxation rate 1 / T1 directly probes such fluctuations, and allows to determine the magnetoelastic coupling strength.