title: From ballistic transport to tunneling in electromigrated ferromagnetic breakjunctions.
abstract: We fabricate ferromagnetic nanowires with constrictions whose cross section can be reduced gradually from 100 x 30 nm(2) to the atomic scale and eventually to the tunneling regime by means of electromigration. The contacts are mechanically and thermally stable. We measure low-temperature magnetoresistances (MR) < 3% for contacts < 400 Omega, reproducible MR variations that are nonmonotonic in the regime 400 Omega - 25 kOmega, and a maximum MR of 80% for atomic-scale widths. These results for devices > 400 Omega differ from previous room-temperature studies of electrodeposited devices. For samples in the tunneling regime, we observe large fluctuations in MR, between -10 and 85%.
authors.affiliation: Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Kirill I
authors.initials: KI
authors.lastname: Bolotin
authors.forename: F
authors.initials: F
authors.lastname: Kuemmeth
authors.forename: Abhay N
authors.initials: AN
authors.lastname: Pasupathy
authors.forename: D C
authors.initials: DC
authors.lastname: Ralph