Magneto-transport behavior of disordered three dimensional Ni_xCo_1-x inverse opal networks

Herein we report on the magneto-transport properties of disordered three dimensional inverse opals (3D-IOs) fabricated by a standard three-probe electro-deposition technique into the interstices of porous membranes made of 150 nm diameter self assembled poly(methylmethacrylate) spheres. This approach has allowed the synthesis of large scale nano composites with exact ferromagnetic Ni_xCo_1−x alloy compositions and complex interconnected structure. Particularly, the microstructure of Co-rich 3D-IOs is consistent with the hexagonal close packed hcp texture and its corresponding magnetoresistance is explained in terms of the hcp Co magnetocrystalline anisotropy contribution. Conversely, the magneto resistive behavior of Ni-rich 3D-IO networks is explained in terms of only their magnetostatic field. The control of these features is made possible by the reduced dimensions of necks and walls, in the 40 nm to 60 nm range, of the 3D-IO structure. Despite the disordered morphology of these 3D-IO nano architectures, their microstructural and magneto-transport properties can be fine tuned due to the reduced nano scale dimensions of the electrical interconnections. These properties have been found to be comparable to those obtained in other 3D networks, making them interesting systems for their potential use for magnetic sensing and spintronic applications. (author)