Magnetic properties of nanometric Fe wires obtained by multiple extrusions

A method for producing arrays of nanometric wires is briefly described, The method consists of extruding a compact containing parallel iron wires spac ed in a copper matrix until the wires become extremely small (10 nm at the ultimate stage), Coercive forces up to 0.04 T are found, A clear shape indu ced anisotropy is observed, The decrease in H-A observed at the smallest di ameters is attributed to wire distortion. The activation volume deduced fro m magnetic after effect measurements is 6x10(4)nm(3). It is much larger tha n the one expected in the case that coherent rotation would occur. Its valu e is rather consistent with a collective magnetization reversal process. Th e angular dependence of H-C approaches a 1/cos theta law, This behavior exc ludes coherent rotation, It is expected whenever the coercive field is much weaker than the anisotropy field in the activation volume.