Relaxation and Landau-Zener experiments down to 100 mK in ferritin -: art. no. 172401

Temperature-independent magnetic viscosity in ferritin has been observed from similar to2 K down to 100 mK, proving that quantum tunneling plays the main role in these particles at low temperature. Magnetic relaxation has also been studied using the Landau-Zener method, making the system crossing zero resonant field at different rates alpha=dH/dt ranging from 10(-5) to 10(-3) T/s and at different temperatures from 150 mK up to the blocking temperature. We propose a T ln(DeltaH(eff)/tau(0)alpha) scaling law for the Landau-Zener probability in a system distributed in volumes, where DeltaH(eff) is the effective width of the zero-field resonance.