title: Magnetic hardening of Fe30Co70 nanowires.
abstract: 3d transition metal-based magnetic nanowires (NWs) are currently considered as potential candidates for alternative rare-earth-free alloys as novel permanent magnets. Here, we report on the magnetic hardening of Fe30Co70 nanowires in anodic aluminium oxide templates with diameters of 20 nm and 40 nm (length 6 μm and 7.5 μm, respectively) by means of magnetic pinning at the tips of the NWs. We observe that a 3-4 nm naturally formed ferrimagnetic FeCo oxide layer covering the tip of the FeCo NW increases the coercive field by 20%, indicating that domain wall nucleation starts at the tip of the magnetic NW. Ferromagnetic resonance (FMR) measurements were used to quantify the magnetic uniaxial anisotropy energy of the samples. Micromagnetic simulations support our experimental findings, showing that the increase of the coercive field can be achieved by controlling domain wall nucleation using magnetic materials with antiferromagnetic exchange coupling, i.e. antiferromagnets or ferrimagnets, as a capping layer at the nanowire tips.
authors.affiliation: Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany.
authors.forename: Sara Liébana
authors.initials: SL
authors.lastname: Viñas
authors.forename: Ruslan
authors.initials: R
authors.lastname: Salikhov
authors.forename: Cristina
authors.initials: C
authors.lastname: Bran
authors.forename: Ester M
authors.initials: EM
authors.lastname: Palmero
authors.forename: Manuel
authors.initials: M
authors.lastname: Vazquez
authors.forename: Behnaz
authors.initials: B
authors.lastname: Arvan
authors.forename: Xiang
authors.initials: X
authors.lastname: Yao
authors.forename: Peter
authors.initials: P
authors.lastname: Toson
authors.forename: Josef
authors.initials: J
authors.lastname: Fidler
authors.forename: Marina
authors.initials: M
authors.lastname: Spasova
authors.forename: Ulf
authors.initials: U
authors.lastname: Wiedwald
authors.forename: Michael
authors.initials: M
authors.lastname: Farle