Heavy rare earth magnets like terbium and dysprosium comprise atom-sized magnetic dipoles sitting in a surrounding electronic 'glue'. This glue is common to all the heavy rare earth elements and makes them chemically very similar. In their paper Eduardo Mendive-Tapia and Julie Staunton find that it both enables the dipoles to interact with each other and that it also responds to the extent and nature of how the dipoles arrange themselves. This feedback sets the main features of the complex magnetic structures that heavy rare metal elements form at various temperatures and under applied magnetic fields. Moreover it explains transitions at critical temperature and field values between, for example, long-ranged, helical magnetic configurations, fan patterns and uniform, all-lined up dipole arrangements. The magnetic properties of materials containing heavy rare earth elements make them indispensable components in materials for many high-tech applications. For example they are in many strong permanent magnets which are used in motors and generators, transducers, magnetomechanical devices etc. A significant factor for these properties is therefore the subtle behaviour of the electronic glue which can be tracked in terms of the changing topology of its Fermi surface.

• Caption to figure: The LMHK plane of the Fermi surface of the electrons in a paramagnetic heavy rare earth metal which shows the 'nesting vector' that characterises a long period helical magnetic state.
• Publication: Eduardo Mendive-Tapia and Julie B. Staunton, Phys. Rev. Lett. 118, 197202, (2017)
• DOI: doi.org/10.1103/PhysRevLett.118.197202