Magnetic Properties of 3d Metal Rods With Composition Gradients Produced by Electroless Deposition

A comparative study of the magnetic properties of arrays of Co–Ni rods with different composition gradients (smooth or step-like) along the rod axes was carried out. Ordered arrays of Co–Ni nanorods with diameters up to 400 nm and 8 µm length were prepared by electroless plating into a porous nuclear-track-etched polycarbonate membrane. The gradient in Co and Ni composition was confirmed by energy-dispersive X-ray analysis. The variation of Co–Ni contents along the long axis of the rods correlates with the gradient of the magnetization within the rod. Magnetization reversal was studied by analyzing the angular dependence of coercivity and using micromagnetic simulations. For both types of gradient rods, reversal occurs by curling. The local magnetic anisotropy field of rods with a step-type gradient is significantly higher than that for rods with a smooth gradient.