Magnetic Field Effects on the Formation and Properties of Nickel Nanostructures

Abstract A facile solvothermal hydrazine reduction route was designed for the synthesis of shape‐controlled one‐dimensional (1D) nickel wires in the presence of magnetic fields. The reaction conditions involved were studied systematically to select the optimal reaction parameters to reveal the effects of weak magnetic fields on the formation and properties of nickel nanostructures. The magnetic‐field‐dependent formation of 1D nickel wires indicated that the reduction of nickel ions with concentration less than 0.21 M preferentially occurs along the magnetic line of force, leading to the formation of uniform 1D wires, whereas higher concentrations could lead to quick reaction in the whole system and formation of isolated particles coexisting with wires composed of microspheres formed along the magnetic line of force. The improved magnetic properties of the sample formed in a magnetic field relative to those of samples formed without an applied field may be due to variation of the magnetic domain structure in the 1D nickel wires. Moreover, it was found that microwave absorption of a 1D nickel wire/poly(methyl methacrylate) (PMMA) composite at 8.5–12.5 GHz was evidently enhanced relative to that of a nickel microsphere/PMMA composite, which indicates that the anisotropic wires are not simply an assembly of particles, but that the magnetic domain structures in wires has been changed by the applied field.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)