Magnetic Fluctuations Measured with X-ray Photon Correlation Spectroscopy
J. B. Goedkoop
University of Amsterdam
This talk will introduce the principle of X-ray photon correlation spectroscopy for the study of magnetic fluctuations and a successful application of this technique to the investigation of such fluctuations in a high-quality epitaxially grown Y/Ho/Y film. The incoherent resonant magnetic diffraction peak of this antiferromagnetic system shows pronounced critical broadening at temperatures around the ordering temperature.
Under coherent illumination, this broadened diffraction peak breaks up in a pronounced speckle pattern that reflects the local structure of the illuminated sample area. By correlating the fluctuations in the speckle intensity we could follow the magnetization dynamics over time scales ranging from seconds to hours. The data indicate a transition from a thermally activated pinned behaviour at low temperatures to a critical fluctuation regime above the ordering temperature.
