Thin film magnetic materials continue to attract significant research attention due their potential for the development of technologically desirable magnetoelectronic, spintronic and spin-orbitronic devices. Such materials gain their magnetic properties from the electronic structure and fundamental physical interactions between neighbouring species in thin film systems.

The role of interfaces in multi-layered materials is important and static properties have been well explored in recent years. Interfacial anisotropy and chirality effects from the Dzyaloshinskii-Moriya interaction are significant examples. Induced moments in non-ferromagnetic layers[1] and even a modification to the damping in NiFe/Cr bilayers[2] has been identified. However, in this latter case the elemental contribution to this dynamic effect is unknown.

With x-ray scattering techniques, the varying penetration depth of the x-ray probe with grazing incidence angle provides depth dependent interrogation of the structure. When performed with varying x-ray polarisation in an applied magnetic field, additional sensitivity to the magnetic moment arises. This makes x-ray reflectivity a valuable tool to interrogate element specific interfacial contributions to the magnetism in thin film multi-layered samples.

Key to the high speed operation of future devices is a solid understanding of the magnetisation dynamics and time-dependent magnetisation processes taking place in thin film multilayered materials. To investigate this temporal behaviour we employ a stroboscopic pump-probe measurement approach. Here, the time structure of x-rays produced by the synchrotron source is synchronised with a pulsed magnetic field with a variable delay from the arrival time of x-ray photons. This allows us to probe the element specific magnetisation dynamics within the layered structure with sub-nanosecond resolution. Results from a NiFe/Cr bilayer interface will be presented.

[1] D.M. Burn, T.P.A. Hase and D. Atkinson, J. Phys.: Condens. Matter 26, 236002 (2014) Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties
[2] J.A. King, A. Ganguly, D.M. Burn, et.al. Applied Physics Letters 104 242410 (2014). Local control of magnetic damping in ferromagnetic/non-magnetic bilayers by interfacial intermixing induced by focused ion-beam irradiation.