We present a study of ballistic conductance through Ni, Co, and Fe nanocontacts within a semiempirical tight-binding model. In our model, both spin channels are treated simultaneously, which allows us to simulate a domain wall pinned in the nanocontact. We observe that the interplay of the contact and the domain wall resistance can produce very large giant magnetoresistance ratios. However, at least within our model, very large giant magnatoresistance appears to be limited to geometries in which the nanocontacts are very narrow and have very small aspect ratios.

• Received 9 June 2003

DOI:https://doi.org/10.1103/PhysRevB.69.094425