Dresden 2006 – scientific programme

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DY: Dynamik und Statistische Physik

DY 45: Soft Matter

DY 45.4: Talk

Thursday, March 30, 2006, 15:15–15:30, SCH 251

Magnetooptics with capped colloids — •Larysa Baraban, Florian Merkt, Björn Biehler, Paul Leiderer, and Artur Erbe — Universität Konstanz, Fachbereich Physik, 78457 Konstanz, Deutschland

Colloidal suspensions are fascinating examples of soft matter, but also model systems for studying the behavior of atoms and molecules. In most cases, the colloidal particles used for these investigations have spherical symmetry. Here we present the fabrication and characterization of magnetically anisotropic particles.
Metallic bi-layers (Ni, Au) are evaporated on top of silica colloids, thus generating hemispheric magnetic “caps”. In order to detect the magnetization of particles we use the magneto-optic (m-o) Faraday effect. Capped particles are placed on a reflecting surface (usually aluminum or silver), evaporated on a m-o active garnet film (YIG). Their magnetic moments induce a distribution of the magnetic field in the m-o film; therefore the Faraday rotation changes from point to point. Reflected by the mirror, polarized light carries information about the local magnetization in the YIG.
As expected, the magnetization of capped colloids displays hysteresis-like behavior. From these data we evaluate the initial magnetic moment and magnetic moment in the saturation regime. The remanent magnetization and coercivity of magnetic particles are estimated as well.
As a possible application, this technique can be used to check the magnetic monodispersity of big particles arrays by a single magnetooptic measurement.