K. J. Merazzo

Dependence of magnetization process on thickness of Permalloy antidot arrays

Nanohole films or antidot arrays of Permalloy have been prepared by the sputtering of Ni80Fe20 onto anodic alumina membrane templates. The film thickness varies from 5 to 47 nm and the antidot diameters go from 42 to 61 nm, for a hexagonal lattice parameter of 105 nm. For the thinner antidot films (5 and 10 nm thick), magnetic moments locally distribute in a complex manner to reduce the magnetostatic energy, and their mostly reversible magnetization process is ascribed to spin rotations. In the case of the thicker (20 and 47 nm) antidot films, pseudodomain walls appear and the magnetization process is mostly irreversible where hysteresis denotes the effect of nanoholes pinning to wall motion.

Micromagnetism of permalloy antidot arrays prepared from alumina templates

Magnetic hysteresis processes of hexagonal arrays of permalloy antidots have been studied by means of micromagnetic simulations as a function of geometrical parameters. The ideal system shows a maximum of the coercive field as a function of the antidot diameter. The simulated magnetic behavior has been compared with experimental values for antidot arrays of permalloy prepared from alumina templates with thicknesses between 2 and 60 nm, showing a monotonic increase of the coercive field as a function of the antidot diameter. We show that the introduction into simulations of the combination of variable antidot diameters from bottom to top due to the fabrication process and, more importantly, large geometrical domains, which break the sample symmetry, solves the discrepancy between the simulations and the experiment.

Micromagnetism of dense permalloy antidot lattices from anodic alumina templates

Hexagonally ordered Py antidot arrays were prepared by sputtering onto anodic alumina membrane templates, with varying antidot diameter and lattice constant parameter. Experimental magnetic characterization together with micromagnetic simulations was performed to unveil the coercivity mechanism. Experimental measurements show that coercivity monotoni- cally increases with the antidot diameter in reasonable agreement with simulations. This is under- stood considering the presence of geometrical micrometric domains with perfect hexagonal order. Contrarily, simulations for a single crystal sample predict that the coercivity should decrease with the antidots diameter. Copyright c EPLA, 2012

Anisotropic magnetoresistance in biphase microwires

The magnetic properties and anisotropic magnetoresistance behavior of biphase microwires with an amorphous FeSiB nucleus are presented. The existence of an external CoNi magnetic layer is shown to modify the magnetoresistive response of the nucleus material by changing the internal anisotropies via magnetoelastic coupling. A careful control of the production parameters allows tailoring of the magnetic properties.