Skip to ContentSkip to Navigation
University of Groningenfounded in 1614  -  top 100 university
About us Latest news News News articles

On ferroelectricity of magnets

29 November 2010

PhD ceremony: Mr. A. Scaramucci, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Thesis: On ferroelectricity of magnets

Promotor(s): prof. M.V. Mostovoy, prof. J. Knoester

Faculty: Mathematics and Natural Sciences

 

Ferroelectric compounds possess a spontaneous and reversible electric polarization, P.Magnetic materials, on the other hand, display a spontaneous order of magnetic dipoles induced by electron spins. The cross-coupling between P and magnetism, which can potentially lead to novel memory storage devices, is found in magnetoelectric compounds, where magentization can be induced by an appliedelectric field (or vice versa), and in so-called magnetic ferroelectrics, where a spontaneous polarization is induced by spin ordering. Understanding the physics underlying the rich variety of observed phenomena in these compounds is both of fundamental and technological interest.

In this thesis we study model Hamiltonians for compounds in which magnetic ordering and electric polarization are coupled. Using symmetry considerations, the form of microscopic couplings between spins and electric polarization are obtained for different systems. These expressions are used to reveal the mechanism behind the magnetoelectric effect in Cr2O3 and to find the origin of so-called electromagnon excitations in YMn2O5. Furthermore, the theoretical analysis of materials with so-called magnetic spiral states allows us to explain a number of recently observed phenomena, in which electric polarization is controlled by an applied magnetic field. These include the rotation of electric polarization by rotating an applied magnetic field, and the clamping of ferromagnetic and ferroelectric domain walls. Finally, novel effects, such as the high-temperature induction of electric polarization by arrays of ferromagnetic domain walls, are predicted.

 

Last modified:13 March 2020 01.16 a.m.
Share this Facebook LinkedIn
View this page in: Nederlands

More news

  • 10 September 2025

    Funding for Feringa and Minnaard from National Growth Fund project Big Chemistry

    Two UG research projects have received funding from the National Growth Fund project Big Chemistry via NWO.

  • 09 September 2025

    The carbon cycle as Earth’s thermostat

    Earth's natural carbon cycle becomes unbalanced if we, humans, continue to release extra carbon dioxide (CO2) into the atmosphere. In this overview article about the carbon cycle, you can find out how Earth generally keeps itself in balance and how...

  • 09 September 2025

    Carbon dioxide’s fingerprint

    In the year 2000, Harro Meijer, Professor of Isotope Physics at the University of Groningen, set up the Lutjewad Measurement Station near Hornhuizen. There, researchers from Groningen are mapping where CO2 in the atmosphere originates and where it...