Low temperature specific heat of the single molecule magnet Fe8

We present low temperature specific heat and ac-susceptibility measurements of Fe8 powdered sample. Below 1.3 K, super-paramagnetic blocking effects and an excess specific heat contribution are observed. The latter is attributed to a splitting of the ground state doublet in an inhomogeneous local field of hyperfine and dipolar origin. The local field contributions are evident at the resonances observed in the field dependent ac-susceptibility and specific heat below 0.5 K. The low temperature Schottky contribution is in agreement with known crystal field parameters of effective spin Hamiltonians proposed to simulate EPR and inelastic neutron scattering experiments.

Graphical abstractLow temperature specific heat of Fe8 results are presented and explained as a low temperature Schottky contribution, splitting of the ground state doublet in the local field of hyper-fine and dipolar origin and superparamagnetic blocking effect.Figure optionsDownload full-size imageDownload as PowerPoint slide