International Journal on Magnetic Particle Imaging IJMPI
Vol. 9 No. 1 Suppl 1 (2023): Int J Mag Part Imag

Short Abstracts

Synthetic Antiferromagnet Disk Particles for Hyperthermia Applications

Main Article Content

Hans J. Hug (Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland), Subas Scheibler (Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.), Inge K. Herrmann (ETH Zürich, ML F18, Sonnegstrasse 3, 8092 Zürich, Switzerland), Dieter Suess (Physics of Functional Materials, University of Vienna Kolingasse 14-16, 1090 Wien, Austria), Michal Krupinski (The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Department of Magnetic Materials and Nanostructures, Radzikowskiego 152, 31-342 Kraków, Poland), Matthias Gräser (Universität zu Lübeck, Ratzeburger Allee 160, 23562 Lübeck. Germany)

Abstract

Heat generation from chemically synthesized superparamagnetic nanoparticles remains limited by the low magnetization of the typically used oxidic materials, the wide particle size distribution, and the narrow shape of their magnetic hysteresis loop.


The overcome these limits, synthetic antiferromagnet magnetic disk particles (SAF MDP) consisting of two ferromagnetic (F) layers separated by a non-magnetic layer were designed. The geometry and magnetic system parameters were optimized via micromagnetic modeling to obtain an antiferromagnetically coupled (zero moment) ground state and an abrupt switching into a ferromagnetically aligned state in an applied field HAF?F to maximize the hysteretic loss.


The magnetic multilayer was sputter-deposited onto a 50nm-thick Ge sacrificial layer on a silicon wafer. Self—assembled polysterene spheres served as an etch mask for the successive nanopatterning of disk-shaped islands. These were then detached from the supporting wafer by dissolution of the Ge layer.


The magnetic properties of the SAF MDP analyzed by vibrating sample and Kerr magnetometry, high-resolution in-field magnetic force microscopy closely matched the design goals and micromagnetic simulation results. A turn-on/turn-off magnetism of the SAF MDP and a hysteretic loss close to the theoretical limit given by the magnetic material with the highest saturation magnetization and a perfectly rectangular hysteresis loop could be demonstrated. Experiments mapping the hysteretic loss of SAF MDP suspensions for different operation conditions are presently underway.  

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