Domains In Epitaxial Films Research Articles

Nanoscale imaging of antiferromagnetic domains in epitaxial films of Cr2O3 via scanning diamond magnetic probe microscopy.

We report direct imaging of boundary magnetization associated with antiferromagnetic domains in magnetoelectric epitaxial Cr2O3 thin films using diamond nitrogen vacancy microscopy. We found a correlation between magnetic domain size and structural grain size which we associate with the domain formation process. We performed field cooling, i.e., cooling from above to below the Néel temperature in the presence of a magnetic field, which resulted in the selection of one of the two otherwise degenerate 180° domains. Lifting of such a degeneracy is achievable with a magnetic field alone due to the Zeeman energy of a weak parasitic magnetic moment in Cr2O3 films that originates from defects and the imbalance of the boundary magnetization of opposing interfaces. This boundary magnetization couples to the antiferromagnetic order parameter enabling selection of its orientation. Nanostructuring the Cr2O3 film with mesa structures revealed reversible edge magnetic states with the direction of magnetic field during field cooling.

Phase engineering in oxides by interfaces

Optical second harmonic generation and piezoresponse force microscopy are used to investigate manifestations of ordered states directly related to the presence of an oxide interface. Three examples, each with a very different scope, are reviewed in order to highlight the richness of interface-related phenomena in oxides. (i) The orbital states involved in the emergence of an interfacial conducting state in LaAlO(3)/SrTiO(3) heterostructures are investigated, which reveal a surprising decoupling of orbital and transport properties; (ii) the distribution of ferroelectric and antiferromagnetic domains in epitaxial films of the multiferroic hexagonal manganites is investigated, which reveals striking differences to the corresponding bulk crystals; and (iii) the distribution of trimerization-polarization domains in the hexagonal manganites is investigated, which reveals the presence of topologically protected domain walls with properties different from the bulk.

Lateral periodicity of elastic domains in MnAs/GaAs(001) epitaxial layers studied by high resolution X-ray diffraction

Abstract Periodic elastic domains in epitaxial films of MnAs(11̅00)/GaAs(001) are studied near the ferromagnetic phase transition. We obtain the period of the domain structure from the observed the X-ray diffraction satellites arising from the lateral periodicity. The application of the X-ray methods provides a high level of accuracy and gives information about average values over areas of several mm2. The observed periods are in a good agreement with those obtained by calculation and minimization of the elastic energy.

Stability diagram for elastic domains in epitaxial ferroelectric thin films

The statics of isolated elastic domains (twins) in epitaxial thin tetragonal films grown on a cubic substrate is investigated theoretically. Different possible variants of the geometric shape of a domain are studied: plate, trapezoidal, and triangular. The nonuniform internal stresses, which also exist in polydomain epitaxial systems, are calculated by the effective-dislocation method. Hence the elastic energies stored in heterostructures with different domains are determined. The equilibrium width of a domain is calculated by minimizing the total internal energy of the heterostructure. Next, the stability diagram for isolated domains in epitaxial films is constructed from energy considerations. It is shown that in a large part of this diagram trapezoidal domains are energetically more advantageous than plate-shaped domains. The effect of an external electric field on the stability of 90° domains in epitaxial ferroelectric films is investigated.