Ferromagnet-Free Magnetoelectric Thin Film Elements

• Main Author: Kosub, Tobias
• Other Authors: TU Chemnitz, Fakultät für Naturwissenschaften
• Format: Doctoral Thesis
• Language: English
• Published: Universitätsbibliothek Chemnitz 2016
• Subjects: Magnetismus; Dünne Schichten; Spintronik; Kontrolle von Magnetismus mit elektrischem Feld; Antiferromagneten; Anomaler Hall Effekt; Magnetischer Proximity Effekt; Zero-Offset Hall; Magnetism; Thin films; Spintronics; Electric field control of magnetism; Antiferromagnets; Anomalous Hall; Magnetic Proximity Effect; ddc:519; ddc:531; ddc:537; ddc:538; ddc:548; ddc:621; Hall-Effekt; Antiferromagnetikum; Magnetspeicher; Magnetoelektronik
• Online Access: http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-215612; http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-215612; http://www.qucosa.de/fileadmin/data/qucosa/documents/21561/20161206_thesis_pc1.pdf; http://www.qucosa.de/fileadmin/data/qucosa/documents/21561/signatur.txt.asc

The work presented in this thesis encompasses the design, development, realization and testing of novel magnetoelectric thin film elements that do not rely on ferromagnets, but are based entirely on magnetoelectric antiferromagnets such as Cr2O3. Thin film spintronic elements, and in particular magnetoelectric transducers, are crucial building blocks of high efficiency data processing schemes that could complement conventional electronic data processing in the future. Recent developments in magnetoelectrics have revealed, that exchange biased systems are ill-suited to electric field induced switching of magnetization due to the strong coupling of their ferromagnetic layer to magnetic fields. Therefore, ferromagnet-free magnetoelectric elements are proposed here in an effort to mitigate the practical problems associated with existing exchange biased magnetoelectric elements. This goal is achieved by establishing an all-electric read-out method for the antiferromagnetic order parameter of thin films, which allows to omit the ferromagnet from conventional exchange biased magnetoelectric elements. The resulting ferromagnet-free magnetoelectric elements show greatly reduced writing thresholds, enabled operation at room temperature and do not require a pulsed magnetic field, all of which is in contrast to state-of-the-art exchange biased magnetoelectric systems. The novel all-electric read-out method of the magnetic field-invariant magnetization of antiferromagnets, so-called spinning-current anomalous Hall magnetometry, can be widely employed in other areas of thin film magnetism. Its high precision and its sensitivity to previously invisible phenomena make it a promising tool for various aspects of thin solid films. Based on this technique, a deep understanding could be generated as to what physical mechanisms drive the antiferromagnetic ordering in thin films of magnetoelectric antiferromagnets. As spinning-current anomalous Hall magnetometry is an integral probe of the magnetic properties in thin films, it offers no intrinsic scale sensitivity. In order to harness its great precision for scale related information, a statistical framework was developed, which links macroscopic measurements with microscopic properties such as the antiferromagnetic domain size.