Combined time-resolved x-ray magnetic circular dichroism and ferromagnetic resonance studies of magnetic alloys and multilayers (invited)

Abstract

We present measurements of element- and time-resolved ferromagnetic resonance (FMR) in magnetic thin films at gigahertz frequencies via an implementation of time-resolved x-ray magnetic circular dichroism (TR-XMCD). By combining TR-XMCD and FMR, using a rf excitation that is phase locked to the photon bunch clock, the dynamic response of individual layers or precession of individual elements in an alloy can be measured. The technique also provides extremely accurate measurements of the precession cone angle (to 0.1°) and the phase of oscillation (to 2°, or ∼5ps at 2.3GHz). TR-XMCD combined with FMR can be used to study the origins of precessional damping by measuring the relative phase of dissimilar precessing magnetic moments. We have used the technique to measure the response of specific elements and separate layers in several alloys and structures, including a single Ni81Fe19 layer, a pseudo-spin-valve structure (Ni81Fe19∕Cu∕Co93Zr7), magnetic bilayers consisting of low damping (Co93Zr7) and high damping (Tb-doped Ni81Fe19) layers joined across a common interface, and elemental moments in Tb-doped Ni81Fe19.