Magnetization of self-organized Ni-nanowires with peculiar magnetic anisotropy

Porous silicon (PS) offering a quasi-regular pore arrangement in the meso-/macroporous regime acts as a matrix for incorporating ferromagnetic nanostructures. The electrochemically fabricated structures are self-assembled and exhibit pores with a diameter tunable between 30 and 100 nm. The subsequent electrodeposition of Ni into these pores leads to a Ni/Si-nanocomposite consisting of Ni-particles and Ni-wires, respectively. The ratio of particles and wires depends on the electrochemical deposition conditions like current density as well as current pulse duration. The different distributions cause a variation of the magnetization curves. Especially in the high. field regime a negative magnetization branch occurs and decreases with increasing amount of particles. This peculiar high field magnetic behavior appears if the external magnetic field is applied perpendicular to the sample surface and is due to antiferromagnetic coupling between the Ni-nanostructures. (C) 2007 Elsevier B.V. All rights reserved.