title: Experimental evaluation of the magnetic properties of commercially available magnetic microspheres.
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.
authors.affiliation: Department of Physics, University of Western Australia, Nedlands, WA 6009, Australia. Joan.Connolly@bristol.ac.uk
authors.forename: Joan
authors.initials: J
authors.lastname: Connolly
authors.forename: Timothy G
authors.initials: TG
authors.lastname: St Pierre
authors.forename: Jon
authors.initials: J
authors.lastname: Dobson
mesh_terms: D001672:Biocompatible Materials / Q000032:analysis* / Q000737:chemistry*; D005290:Ferric Compounds / Q000032:analysis*; D008280:Magnetics / Q000295:instrumentation*; D008422:Materials Testing; D010316:Particle Size
chemical_list: D001672:Biocompatible Materials; D005290:Ferric Compounds; C000499:ferric oxide