In the field of spintronics, understanding the fundamentals of spin physics is a crucial ingredient in utilising the spin degree of freedom in future electronic devices. Ferromagnetic materials and nanocontacts have traditionally played a crucial role in the creation of spin, its manipulation and its detection.
In this talk I will firstly give an introduction to the techniques we have been using in the past few years to investigate spin dependent phenomena using ferromagnetic contacts. We use optical spin orientation in III-V semiconductors to create a photoexcited spin carrier population in ferromagnetic-metal/semiconductor heterostructures. This constitutes our source of spin which, when used in appropriate heterostructures/geometries, has led to many investigations. I shall review the most important of these investigations such as the first demonstration of spin transport in Ge at room temperature, the role of interface scattering in spin transport.
In the main part of my talk I will present a new approach where the above techniques are combined with ferromagnetic resonance (FMR) measurements. Measurements are carried out at room temperature on epitaxial ferromagnet/GaAs heterostructures grown by molecular beam epitaxy. The spin polarised carrier population photoexcited at the interface affects the ferromagnet magnetisation and its dynamics via an interface exchange interaction. The exchange field contributes to the internal effective field of the ferromanget and it can be measured in the FMR response.We have demonstrated an effective exchange field of the order of tens of Gauss. The technique offers another avenue of the optical control of magnetisation via exchange fields.