Models for nanomagnetic particles EU-funded scientists modelled the behaviour of tiny magnetic particles in strong alternating magnetic fields with a view to developing data storage devices and cancer therapies. Health © Thinkstock Ferromagnetic nanoparticles are tiny iron-containing molecules that become magnetised when exposed to an external magnetic field but lose their magnetism when the field is removed. In addition, their magnetism can be reversed at certain temperatures. This makes them useful for applications that require magnetisation switching from one polarity to the other (e.g. magnetic data storage) and for magnetically induced heat generation. When ferromagnetic nanoparticles are subjected to cyclic magnetisation reversals, a dynamic magnetic hysteresis (DMH) loop occurs. This means the particles retain some magnetic memory after the magnetic field is switched off. Because such systems are dependent on the stimulus, they do not have predictable behaviours, making theoretical modelling difficult. For the EU-funded project DMH (Nonlinear dynamic hysteresis of nanomagnetic particles with application to data storage and medical hyperthermia), scientists modelled the behaviour of magnetic nanoparticles subjected to strong alternating current magnetic fields. They then compared their models with experimental observations. Researchers first developed models for the DMH behaviour of individual nanoparticles, and then extended their calculations to an assembly of nanoparticles in alternating magnetic fields. They also looked at how magnetic particle assemblies placed in solid or liquid suspensions change over time. These models can be used to describe magnetic-based nanosystems in different media or environments, for example magnetic data storage discs or medically useful liquids. Nanomagnetic particles show particular promise in medicine by magnetically generating heat to treat cancer. In this case, ferromagnetic nanoparticles injected by syringe into a tumour absorb alternating current magnetic field energy, releasing enough heat to kill cancer cells. DMH's models of the magnetic behaviours of nanoparticles in different media will likely impact both biomedical and data technology fields. Keywords Nanomagnetic particles, magnetic fields, data storage, cancer, ferromagnetic, dynamic magnetic hysteresis
