Ballistic magnetoresistance in transition-metal nanocontacts: The case of iron

2 pages, 2 figures.This letter shows that the ballistic magnetoresistance of Fe at room temperature and low magnetic fields is ten times smaller than for Ni and Co. The results are well explained by theory that provides a global understanding for 3d transition metals because, for Fe, the ratio of majority to minority spins at Fermi level is much smaller than for Ni and Co. The data indicate that conduction is carried out by majority d electrons in the case of Fe, in contrast to what happens for Ni and Co.This work has been supported by the Spanish DGICyT.Peer reviewe