Comment on Magnetic Relaxations of Antiferromagnetic Nanopar(5)

We have carried out in ferritin the Field-Cooling method and data analysis proposed by Mamiya et al. (Phys. Rev. Lett. 88, 67202 (2002) at T = 5 K in order to check the time magnetic relaxation of these antiferromagnetic nanoparticles as a function of the

Figure 1: del Barco et al.

1.2 1.1 1.0 1.0

Thermal relaxation

S(H=-H )/ S(H=0)

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 100 200 300 400 500 600 700 800

f

Resonant tunneling

f

0

T= 5K H0 (Oe)