Congratulations to Michael Grimes who has had his latest research published in Nature Scientific Reports: “Determination of sub-ps lattice dynamics in FeRh thin films” by M. Grimes, H. Ueda, D. Ozerov, F. Pressacco, S. Parchenko, A. Apseros, M. Scholz, Y. Kubota, T. Togashi, Y. Tanaka, L. Heyderman, T. Thomson and V. Scagnoli. You can view the paper online here.

Abstract: Understanding the ultrashort time scale structural dynamics of the FeRh metamagnetic phase transition is a key element in developing a complete explanation of the mechanism driving the evolution from an antiferromagnetic to ferromagnetic state. Using an X-ray free electron laser we determine, with sub-ps time resolution, the time evolution of the (–101) lattice diffraction peak following excitation using a 35 fs laser pulse. The dynamics at higher laser fluence indicates the existence of a transient lattice state distinct from the high temperature ferromagnetic phase. By extracting the lattice temperature and comparing it with values obtained in a quasi-static diffraction measurement, we estimate the electron–phonon coupling in FeRh thin films as a function of laser excitation fluence. A model is presented which demonstrates that the transient state is paramagnetic and can be reached by a subset of the phonon bands. A complete description of the FeRh structural dynamics requires consideration of coupling strength variation across the phonon frequencies.