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Invited Lecture

Vortex-antivortex topological structures in multiferroic tunnel junctions

Thursday (08.06.2017)
09:10 - 09:50 Förde II + III
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Line-Up:
12:20 Invited Lecture Similarities and differences between magnetic hysteresis and hysteresis in phase transformations 0 Richard James
13:00 Invited Lecture Discovery and Design of Multifunctional Materials using Combinatorial and High-Throughput Experimentation 1 Prof. Dr. Alfred Ludwig
15:10 Invited Lecture Tuning Mechanical Properties of Spider Cuticle by its Composition and by Structural Gradients 0 Dr. Yael Politi
15:50 Invited Lecture Surfaces and Gels for controlling Calcium Phosphate Deposition 0 Prof. Dr. Andreas Taubert
17:40 Invited Lecture Probing the Structure and Dynamic Behaviors of Ferroelectrics by Electron Microscopy with Atomic Resolution in Real Time 0 Prof. Xiaoqing Pan
18:20 Invited Lecture Magnetoelectric Composites for Energy Harvesting 1 Robert E. Hord, Jr. Professor Shashank Priya
19:40 Invited Lecture Declamping in Lead Magnesium Niobate – Lead Titanate Films 1 Prof. Susan Trolier-McKinstry
20:20 Invited Lecture Integrated Magnetics and Multiferroics for Compact and Power Efficient Sensing, Power, RF, Microwave and mm-Wave Electronics 0 Prof. Nian X. Sun
21:00 Invited Lecture From Maxwell’s displacement current to nanogenerator driven self-powered systems and blue energy 0 Prof. Zhong Lin Wang
21:40 Invited Lecture Magnetoelectric Composites: from Sensors to Sensor Systems 0 Prof. Dr.-Ing. Gerhard Schmidt
22:20 Invited Lecture Metal–insulator transition in vanadium oxides films and its applications 1 Dr. Keisuke Shibuya
00:20 Invited Lecture In operando photoemission spectroscopy of PMN-PT interfaces 0 Prof. Dr. Kai Rossnagel
08:30 Invited Lecture Titanium-Tantalum High Temperature Shape Memory Spring Actuators 1 Prof. Dr. Gunther Eggeler
09:10 Invited Lecture Vortex-antivortex topological structures in multiferroic tunnel junctions 1 Dr. Ana Sanchez
09:50 Invited Lecture Artificial Ferroic Systems 1 Prof. Laura Heyderman
17:40 Invited Lecture Biomimicry at the molecular level: Molecularly imprinted polymers as synthetic antibody mimics 0 Karsten Haupt
Session Chair
Topic Invited Lecture:
Belongs to:


J.J.P. Peters, G. Apachitei, R. Beanland, A. Sanchez, M. Alexe
1 Department of Physics, University of Warwick, Gibbet Hill Road, CV4 7AL Coventry, UK  

It  has  been  theoretically  shown  that  in  very  thin  and/or  small  systems  the  formation  of ferroelectric  domain  walls  is  not  energetically  favourable.  Instead  vortex-type  structure, involving polarization curling at unit cell, will form. [1] This has been recently shown at all scales, from macroscopic to medium range super-lattices and atomic scale.[3-5] Arguably, all reports  on  atomic  scale  curling  of  polarisation  and  vortex  structures  are  on  systems  without electrodes.  Whilst  this  favours  vortex  structures  through  enhancement  of  depolarising  fields, manipulation and real use of these vortices necessitates metal electrodes to apply electric fields. 

The screening effect of free carriers in the electrodes will apply a different set of constraints to those found in previously studied vortex structures. This raises the fundamental question of the stability of these vortex structures in metal-ferroelectric-metal, i.e. capacitor, devices.   

Here  we  discuss  occurrence  and  thickness  dependence  of  topological  features  in multiferroic  tunnel  junction  devices  with  ultra-thin,  respectively  3,  6  and  9  unit  cells  (u.c.), PbTiO 3   films  sandwiched  between  Co  and  La 0.7 Sr 0.3 MnO 3   (LSMO)  electrodes.  The  structural data acquired using aberration-free scanning transmission electron microscopy (STEM) will be presented  and  discussed  in  relation  with  electrical  characteristics  of  the  multiferroic  tunnel junctions.  

As pointed recently, [6] the present study might have implications in defining a new state of matter in polar materials. The presence of these chiral topological states in bare capacitors, i.e.  metal-ferroelectric-metal  heterostructures,  opens  avenues  in  electrical  control  including local switching of chirality.

References

[1] I. Naumov, I. Bellaiche, and H. Fu, Nature (London) 432,737 (2004).
[2] R. G. P. McQuaid et al., Nat. Commun. 2, 404 (2011).
[3] Y-L. Tang et al. Science 348, 547 (2015).
[4] C.-L. Jia, et al., Science 331, 1420–1423 (Mar. 2011).
[5] J.J.P. Peters et al., Nature Communication, in press.
[6] A. K. Yadav, et al, Nature doi:10.1038/nature16463 (2016)

 

 

Speaker:
Dr. Ana Sanchez
University of Warwick
Additional Authors:
  • J.J.P. Peters
    University of Warwick
  • G. Apachitei
    University of Warwick