We present the application of x-ray magnetic circular dichroism (XMCD) to two intriguing areas of magnetism: magneto structural phase transitions and magnetization dynamics. In the first part, we will discuss the intriguing ordered alloy FeRh, which exhibits an unusual first order antiferromagnetic (AF) to ferromagnetic (FM) phase transition at ~380 K. In epitaxial thin lms of FeRh, XMCD spectra acquired in surface- and bulk-sensitive modes reveal an unexpected persistence of a FM phase in the near-surface region. The magnitude of this effect is dependent on the capping layer for the epitaxial films, and hence investigations are currently underway to examine the effect of surface strain in nucleating the AF to FM phase transition. In the second part of the talk, we will present our implementation of combined time-resolved x-ray magnetic circular dichroism (tr-XMCD) and ferromagnetic resonance (FMR), which produces a new and powerful tool for examining the dynamics of heterogeneous magnetic materials. The excellent resolution of the technique,in both precession amplitude and phase, enables innovative studies of intrinsic and extrinsic damping mechanisms in FM materials. We will present a few examples of our work in alloy systems and magnetic multilayer structures, and discuss prospects for future measurements.
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