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Magneto-Seebeck Microscopy


In scanning probe microscopy (SPM) images of surfaces are created by moving a tip across the surface. Research in SPM aims to find suitable tips and physical interaction mechanisms which uncover specific surface properties. An important and proven method for mapping the magnetic order of ferromagnetic surfaces is magnetic force microscopy based on the magnetic dipole interaction. The antiferromagnetic order is one of the surface properties which has so far been difficult to image due to the lack of magnetic dipole interaction with magnetic tips.

For the measurement of antiferromagnetic order in SPM a novel contrast mechanism has been introduced by combining the magneto-Seebeck effect with local heat gradients. Here, the thermal gradient is created when a metal-coated SPM tip interacts with an infrared laser, inducing an optical near field at the apex of the tip. Simultaneously, the voltage VT induced across the sample is recorded. Antiferromagnetic order is characterized by the formation of domains which possess a certain magnetic orientation and a corresponding magneto-Seebeck coefficient. Moving the tip across a region where a domain changes its orientation a characteristic modification in the voltage, VT, is created. In this way, Magneto-Seebeck Microscopy can characterize antiferromagnetic order.

The method has recently been used to image domains in a 20-nm thick antiferromagnetic layer of CuMnAs as well as their manipulation by electric current pulses. It will be a primary tool for future investigations into the physical origins of novel switching mechanisms within the DFG project “Quench-switching of antiferromagnets explored with high spatial and temporal resolution” (KA 2866/2-1), which will be carried out together with the Universities of Regensburg (Prof. Wunderlich) and Mainz (Prof. Sinova). Such switching mechanisms are important building blocks in the emerging field of antiferromagnetic spintronics which aims for high-speed operation combined with neuromorphic memory characteristics.

The research was performed by a research team from the Czech Republic, Germany, Spain, and the United Kingdom in which the working group 7.11 IR Spectrometry participated.


T. Janda, J. Godinho, T. Ostatnicky, E. Pfitzner, G. Ulrich, A. Hoehl, S. Reimers, Z. Šobáň, T. Metzger, H. Reichlová, V. Novák, R. P. Campion, J. Heberle, P. Wadley, K. W. Edmonds, O. J. Amin, J. S. Chauhan, S. S. Dhesi, F. Maccherozzi, R. M. Otxoa, P. E. Roy, K. Olejník, P. Němec, T. Jungwirth, B. Kaestner, and J. Wunderlich, "Magneto-Seebeck microscopy of domain switching in collinear antiferromagnet CuMnAs,"
Phys. Rev. Mater. 4, 94413 (2020), Opens external link in new windowhttps://doi.org/10.1103/PhysRevMaterials.4.094413


B. Kästner, 7.11, E-Mail: Opens local program for sending emailBernd.Kaestner(at)ptb.de


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