Affiliations: Department of Physics, University of Western Australia, Nedlands, WA 6009, Australia | Institute for Science & Technology in Medicine, Keele University, Thornburrow Drive, Hartshill, Stoke-on-Trent, ST4 7QB, United Kingdom
Note: [] Present addresses: H.H. Wills Physics Laboratory, Tyndall Avenue, University of Bristol, Bristol, BS8 1TL, United Kingdom.
Note: [] Corresponding author: Joan Connolly, H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, United Kingdom. Tel.: +44 117 954 6886; Fax: +44 (0) 117 925 5624; E-mail: [email protected].
Abstract: The magnetic properties of 5 commercially available magnetic microsphere samples are tested and compared with those stated by their manufacturers. A suspension of magnetic, iron oxide nanoparticles is studied for comparison. Two of the microsphere samples have magnetic properties which do not support the manufacturer's claims of superparamagnetism. The remaining 3 microsphere samples as well as the nanoparticle suspension are superparamagnetic or ferromagnetic as claimed by the manufacturers. Field cooled and zero field cooled magnetisations indicate that the non-superparamagnetic microsphere samples contain blocked magnetic particles at room temperature. This observation is supported by the open hysteresis loops of the room temperature, field dependent magnetisation measurement. There is a significant paramagnetic component in the superparamagnetic microspheres. This is also present to a lesser extent in a nanoparticle suspension.
Keywords: Microspheres, magnetic, iron oxide nanoparticles, physical properties
