Angular dependence of coercivity and remanence of Ni nanowire arrays and its relevance to magnetoviscosity

Abstract

Ni nanowire arrays with varying wire dimensions (diameter d, length l) and center-to-center distances d CC were synthesized by pulsed electrodeposition of Ni in porous Al templates. The magnetization-reversal behavior of the arrays was investigated by means of magnetometry for different angles θ between the wire axes and the applied magnetic field. The functional dependences of the characteristic parameters coercivity H C( θ) and reduced remanence m R /m S( θ) exhibit a strong dependence on the wire dimensions and the center-to-center distance. For instance, for nanowire arrays with d=40 nm, d CC=100 nm, and for θ=0°, the coercivity takes on a rather large value of μ 0 H C=85 mT and m R /m S≅94%; reducing d CC to 30 nm and d to 17 nm results in μ 0 H C=49 mT and m R /m S≅57%, an observation which suggests an increasing magnetostatic interwire interaction at increased ( d/ d CC)-ratio. The potential application of nanowires as the constituents of ferrofluids is discussed.