Magneto-optic diffraction by flat metallic thin films We obtain pure magneto-optic diffraction by a totally flat and optically homogeneous magnetic surface in which an array of ordered domains is artificially induced. The periodic magnetic distribution is obtained by coupling magnetically an array of magnetic elements to a flat and continuous ferromagnetic layer. When the magnetization is modulated periodically by an external field, the local reflectivity varies accordingly and a diffraction pattern appears. The appearance of this diffraction pattern can be controled by an externally applied magnetic field, being able to switch it ON and OFF. This effect could be useful for magneto-optical switches.
Optical and magneto-optical properties of magnetic nanowire arrays: Due to the nanowire geometry the arrays show different respose depending on the polarization orientation of the incident light, which leads to a high anisotropy of both their optical and magneto-optical properties. In this arrays samples a strong increase of the magneto-optical activity is clearly observed with respect to the bulk material which is associated to surface plasmon resonance of the nanowires. We use magneto-optic kerr spectroscopy and ellipsometry to characterize  these samples.
Optical switches: When a strong uniform magnetic field is applied on a magnetic fluid, the magnetic nanoparticles will form fibrillated structures aligned with the field. These oriented structures lead to linear dichroism, that is, greater absorption along the long-axis of those field-induced structures than along the perpendicular direction. We study the dynamical behaviour of a highly diluted ferrofluid in direct contact with an array of magnetic micro-squares. In our system nanoparticles in the ferrofluid are pulled by magnetic field gradients created at a micromagnet array immersed in the fluid. Moreover, periodic distribution magnetic fringe fields at domain walls and edges of the microsquares create linear nanoparticles chains. This periodic magnetic chains induce clear changes on the transmitted and diffracted light that is analyzed as a function of the different diffraction orders. This technology could be use to create optical switches.
Magnetic domain visualizaton with kerr microscopy We study the magnetic domains in micropatterned magnetic thin films by using a Kerr microscopy setup. We meassure the change  in reflectivity due to the change in the magnetization direction.

Collaborators

Instituto de Microelectronica de Madrid-CSIC, Fernando Briones, Gaspar Armelles.

Publications 

• Magneto-optical properties of nickel nanowire gratings, Appl. Phys. Lett. 83 (2003) 4547-4549
• Pure magneto-optic diffraction by a periodic domain structure, Nanotechnology 14 (2003) 239-244

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