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MA: Fachverband Magnetismus

MA 15: Spin structures and Magnetic Phase Transitions

MA 15.8: Vortrag

Dienstag, 1. April 2014, 11:30–11:45, HSZ 403

Restoration of 2D Ising criticality in dipolar-frustrated ferromagnetic films — •Danilo Andrea Zanin¹, Niculin Saratz¹, Boris Sangiorgio¹, Thomas C.T. Michaels², Alessandro Vindigni¹, Urs Ramsperger¹, and Danilo Pescia¹ — ¹ETH Zurich, Switzerland — ²University of Cambridge, United Kingdom

For about three decades the quest for novel paradigms for magnetostorage and spintronics has driven the development and investigation of magnetic nanostructured materials. For instance, the study of films magnetized in plane led to the observation of the two-dimensional Ising critical behavior. In films with easy axis directed out of plane the magnetization spontaneously splits into domains because of the competition between short-range exchange coupling and long-range dipolar interaction. A shrinking of the magnetic domains of in these films with increasing temperature was already observed, e.g., in Fe/Cu(001) samples by means of Scanning-Electron-Microscopy with Polarization Analysis (SEMPA). This phenomenon drives the occurrence of re-entrant transitions of magnetic-domain patterns. However, approaching the Curie temperature, magnetic domains become mobile within the timescale of the experiment, which consequently blurs the SEMPA images. In order to extend the phase diagram to higher temperatures, we performed Magneto-Optic Kerr Effect (MOKE) experiments. Even though our MOKE setup does not allow a direct visualization of micrometric magnetic domains, by means of statistical analysis of the large data set, we identify clearly the transition between uniform to domain phase as a function of temperatures and applied magnetic field.