Department Spin and Topology in Quantum Materials

χ_ac(T) in Fe microstructures

A fundamental question in ferromagnetic systems with reduced dimensions is, whether magnetic properties vary laterally at the edges of the sample, at defects or at steps due to the underlying substrate. Due to changes in the local fluctuation rate of the magnetic moments, the Curie Temperature (TC) is a good quantity to detect such variations. Here we use x-ray photoelectron emission microscopy to image local variations of TC in micro-structured Fe films.

• Figure 1: Fe grown in-situ on pre-structured Si substrates Þ topography avoids magnetic coupling but allows to measure film/structures simultaneously.
• Figure 2: Curie temperature (TC) determined from fit to Curie-Weiss law of the spatially resolved ac magnetic susceptibility (cac) signal in the paramagnetic phase (thus avoiding the influence of the local demagnetization fields below TC)
• Figure 3: cac signal as a function of Temperature (Hac = 0.1 mT at 80 Hz)

_{O. Sandig, J. Herrero-Albillos, F. Kronast, F. Römer, M. Farle}