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Séminaire de groupe

Shapeable magnetoelectronics
Denys Makarov
Institute for Integrative Nanosciences, Dresden
lundi 12 décembre 2011 , 10h00
Salle de séminaire du groupe de Physique Statistique

Shapeable electronic systems have gained substantial interest over the last years due to exciting new applications offered by arbitrary surface geometries possible after fabrication [1]. The aim of the present work is to add a new member to the family of shapeable electronics &#8211; the shapeable magnetic sensor. Layered magnetic structures revealing a giant magnetoresistance (GMR) effect are crucial components of magnetic sensor devices. Currently, GMR sensors are fabricated on rigid inorganic substrates. We aim on the realization of shapeable magnetoelectronics with a strong emphasize on fabrication of (i) elastic GMR sensors and (ii) rolled-up GMR sensors, which can find a straightforward application for in-flow detection of magnetic objects.We fabricated [Co/Cu] and [Py/Cu] GMR multilayers on free-standing elastic Poly(dimethylsiloxane) (PDMS) membranes. The GMR performance of [Co/Cu] multilayers on rigid silicon and on free-standing PDMS is similar and does not change with tensile deformations up to 4.5% [2]. Mechanical deformations imposed on the sensor are totally reversible, due to the elasticity of the PDMS membranes. This remarkable performance upon stretching relies on a wrinkling of GMR layers on top of the PDMS membrane. A conceptually new approach for the detection of magnetic objects flowing through a fluidic channel was introduced relying on stretchable magnetic sensor wrapped around a capillary tubing. Thus, the stray fields induced by the flowing magnetic objects can be detected virtually in all directions (isotropic sensitivity), which is unique for the elastic sensor compared to rigid planar counterparts. In addition, recent advances in fabrication of a rolled-up GMR sensor will be reviewed [3]. The application of the fabricated device for the in-flow detection of magnetic particles will be in the scope of the talk. For the purpose of the study, the sensitivity of the GMR sensors was optimized by using [Py/Cu] multilayers coupled in the second antiferromagnetic maximum. Furthermore, the device includes two rolled-up and two planar GMR sensors connected in a bridge configuration, which not only improved the electrical performance of the sensor but also allowed for better thermal stability, which is crucial for biological applications. For a proof-of-concept, in-flow detection of CrO2 nanoparticles particles embedded in a polymer shell was carried out.<br> [1] R. H. Kim et al., Nature Mater. 9, 929 (2010).<br> [2] M. Melzer et al., Nano Letters 11, 2522 (2011).<br> [3] I. Mönch et al., ACS Nano 5, 7436 (2011)



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