Temperature-independent magnetic viscosity in ferritin has been observed from ∼ 2 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, α = dH/dt, ranging from 10 −5 to 10 −3 T/s, and at different tempera...
