Novel heat activated nanomagnetic exchange springs for data storage
Thin film magnetic exchange spring systems are key components of the modern hard disk drive and have real potential in spintronic applications and high energy produce permanent magnets. These systems are highly desirable as they both retain their magnetic orientation over very long times (many years) and can be switched by magnetic fields available from technologically realizable devices (< 2 Tesla), which is a rare combination. In the simplest systems, the exchange spring is constructed from three layers: a soft layer, a hard layer and a layer to control the exchange coupling energy between these layers.
The aim of this project is to explore a brand new class of magnetic exchange springs where the coupling between the ferromagnetic layers is switched on and off by the application of heat. This would, for example, open the possibility of storing data at densities much higher than are available with current technology.
There are a number of approaches to exploring heat activated coupling in thin magnetic films and the two most promising are:(1) based on materials that show a change in magnetic phase from an antiferromagnet to ferromagnet such as FeRh.
(2) changing the electronic structure of the coupling layer using ceramic materials with a negative thermal expansion coefficient.
This works by coupling/decoupling the magnetic components of the magnetic exchange spring structure through a conducting-to-insulating phase transition.
This project is experimental with the opportunity to use state-of-the-art equipment in sputtering thin films and magnetic characterization & physical characterisation. Specially, the research will consist of designing, making and characterizing new thin film exchange springs based on FeRh and NdO. There will be opportunities to use large scale X-ray and neutron scattering facilities as part of the characterization work.
This project forms part of a larger activity in collaboration with the theory group of Dr. Hrkac at the University of Exeter, UK. It therefore offers excellent opportunities to work with both postdoctoral and PhD experimentalists in Manchester and micromagnetic modelers in Exeter providing a very rich experience.