FERROIX

The "ferroix" group focuses on fundamental and functional properties of so-called "ferroic" materials (i.e., ferroelectrics, ferro-/antiferro-/ferrimagnetics, ferroelastics, or multiferroics) and of complex oxides (i.e. perovskite oxides) in general. For that purpose a variety of experimental techniques is frequently applied:

• piezoresponse force microscopy (PFM),
• conductive atomic force microscopy (c-AFM),
• Cherenkov second-harmonic generation (CSHG) microscopy,
• optical coherence tomography (OCT),
• current-voltage spectroscopy (with/without optical excitation),
• photoluminescence spectrocopy. 

Among others, the ferroix group works on the following topics:

The ferroelectric model system lithium niobate (LiNbO₃, LNO)

• visualisation of the domain- and domain wall structure
• comprehensive analysis of the domain wall conductivity and its tunability
• investigation of the influence of doping on the functional properties
• comparison to other ferroelectric systems, such as
  barium titanate (BaTiO₃, BTO),
  lithium tantalate (LiTaO₃, LTO),
  strontium barium niobate (SBN),
  lead magnesium niobate-lead titanate (PMN-Pt),
  lead zirconate titanate (PZT)

Electronic surface and interface defect states in perovskite heterostructures

• surface photovoltage (SPV)- and photoconductivity spectroscopy of the surface states of the model perovskite strontium titanate (SrTiO₃)
• comparative analysis of the interface states in heterostructures such as LaAlO₃/SrTiO₃ or mixed-valence manganites/SrTiO₃

Tuning of the ferroic properties by external mechanical stress

• ferroelectric-hysteresis measurements under stress induced by a bending stage (experiments on the model systems bismuth ferrite and lithium niobate)

Investigation of ferroelectric-magnetic hybride systems

• studied system so far: nickel-barium titanate (Ni-BaTiO₃)

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