  Recent experiments in approximately 10nm size electrodeposited Ni-Ni
nanocontacts have shown ballistic magnetoresitance values of 700% stable during
a week (Garcia et al Appl. Phys. Lett. 79, 4550(2001) and very recently up to
3000% (Chopra and Hua, Phys. Rev. B 66,020403-1 (2002)). These values can
provide very interesting magnetoelectronic devices integrated in the
terabyte/square inch. Scattering in thin domain wall of the Ni-Ni nanocontacts,
or quantized effects phenomena do not explain these values. An explanation is
presented that requires the existence of a very thin, less than 1nm, dead
magnetic layer grown during the electrodeposition process that is transparent
to the electrons and has two roles: one, is to conserve spin in the electron
conduction and the other, is to change and increase the polarization at Fermi
level in the Ni.
