We are happy to invite you to the following ICMAB Invited Seminar:
The seminar will take place at the Sala d'Actes MATGAS and online:
by Silvia Damerio, Zernike Institute for Advanced Materials, University of Groningen, Groningen, NL
Tuesday, 2 November 2021, 11 am
ICMAB-Sala d'Actes MATGAS and Online by Zoom. Register here to attend.
Periodic structures and patterns are ubiquitous in solid state systems and evolve similarly under external perturbations, suggesting an underlying universal principle. Spatial modulations arise from the presence of competing interactions between the constituting elements of the system at different length scales. In magnetic materials these interactions include magnetic exchange between spins, anisotropy and dipolar fields and are responsible for the formation of complex spin textures and domain patterns. Similarly, in ferroelectrics the interplay between depolarizing fields and elastic energy generates ferroelectric domains and domain walls. Furthermore, when ferroic materials are grown in thin film form, the additional contributions of shape anisotropy and strain can lead to the formation of new phases. In this talk, thin films of ferroic oxides displaying modulated phases are discussed, focusing on two exemplary systems.
The first system is the antiferromagnet CaFe2O4, characterized by two differently modulated spin arrangements that coexist over a large temperature range . The magnetic properties of the films are investigated by means of several complementary techniques, including Mossbauer spectroscopy and spin-Hall magnetoresistance measurements, that reveal the presence of long-range antiferromagnetic ordering as well as a net magnetization.
The second system is thin films of the ferroelectric/ferroelastic BaTiO3, in which compressive strain from a crystalline substrate induces the formation of periodic stripe domains. Here, the evolution of the domain structure is studied across the phase transition between a purely in-plane ferroelectric phase at low temperature and an alternating in-plane and out-of-plane phase at high temperature. Upon heating and cooling, the equilibrium periodicities are reached by means of period-doubling cascades, a feature of systems approaching chaos.
 Damerio, S. et al. Npj Quantum Materials 5 (33), (2020)
 Lane, H. et al., Phys. Rev. B, 104, 104404 (2021)
 Everhardt, A. S., Damerio, S. et al. Physical review letters 123, 087603(2019)
Hosted by Can Onur Avci, MULFOX group, ICMAB-CSIC