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

Ni nanowire arrays with varying wire dimensions (diameter d, length l) and center-to-center distances dCC 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 y between the wire axes and the applied magnetic field. The functional dependences of the characteristic parameters coercivity HC(theta) and reduced remanence m(R)/m(S)(theta) 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 theta = 0 degrees, the coercivity takes on a rather large value of mu H-0(C) = 85mT and m(R)/m(S) congruent to 94%; reducing d(CC) to 30nm and d to 17nm results in mu H-0(C) = 49mT and m(R)/m(S) congruent to 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. (c) 2007 Elsevier B. V. All rights reserved.