Fabrication, Micro-patterning and Use of High Performance NdFeB Micro-magnets

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Contents of the Talk

The emergence of rare earth transition metal (RE-TM) magnets almost 50 years ago revolutionised the design and fabrication of macroscopic machines such as motors and generators. These magnets are now used in diverse applications and are key components of today’s green energy landscape (electric bikes, hybrid electric vehicles, wind turbines). Downscaling the size of high performance RE-TM magnets to the micro-meter scale offers enormous potential for the development of magnetic micro-devices (sensors, motors, actuators…) with potential applications in areas as diverse as telecommunications, consumer electronics, energy management and bio-technology. In this presentation I will review our activities concerning the fabrication, micro-patterning and charcterisation of NdFeB micro-magnets. I will show how triode sputtering can be used to fabricate NdFeB films as thick as 50 µm having excellent extrinsic properties [1]. The high deposition rates achievable with this technique, together with the fact that homogeneous properties can be achieved over a large surface area, make it particularly well suited to the batch fabrication of micro-magnets destined for integration into micro-scaled devices. I will finish up by showing examples of the use of NdFeB micro-magnets in bio-medical applications and will discuss their on-going integration into prototype Micro-Electro-Mechanical-Systems (MEMS).

Figure 1. Plane-view optical images of a 50 µm thick NdFeB deposited on a pre-patterned 100 mm Si substrate together with a cross-sectional scanning electron microscope image of a few micro-magnets and a Magneto-Optical image of the stray magnetic field produced by a part of the film.

[1] Frederico O. Keller, Richard Haettel, Thibaut Devillers and Nora M. Dempsey, Batch fabrication of 50 µm thick anisotropic Nd-Fe-B micromagnets, IEEE Transactions on Magnetics 58 (2022) 2101005

Short CV

Nora Dempsey received her PhD from Trinity College Dublin in 1998 and her HDR (Habilitation à Diriger des Recherches) from Université Joseph Fourier, Grenoble in 2012. Following her thesis, she was a Marie Curie postdoctoral fellow at Laboratoire Louis Néel, CNRS in Grenoble. She was hired as a Junior Scientist (Chargée de Recherche) at CNRS in 2001 and was promoted to Senior Scientist (Directeur de Recherche) in 2014. She is a member of the Micro and Nano Magnetism group at Institut Néel. Her research interests include the study and development of functional magnetic materials in film form, with a particular emphasis on hard magnetic materials.