Application of strain to orbital-spin-coupled system MnV₂O₄ at cryogenic temperatures within a transmission electron microscope

The impact of mechanical stress on the morphology of crystallographic and magnetic domains in shape-controlled specimens of an orbital-spin-coupled system, MnV₂O₄, was examined by cryogenic Lorentz microscopy. Because of the difference in thermal expansion coefficients of MnV₂O₄ and the supporting Mo mesh, compression on the order of 0.01% was applied to the thin-foil specimens near the structural/magnetic phase transformation temperatures. The extent of compression was comparable to the lattice striction associated with the cubic-to-tetragonal phase transformation in MnV₂O₄. The applied strain thus clearly influenced themorphology of crystallographic domains (i.e. twinning configuration in the tetragonal phase) produced during cooling. The magnetic domain structure was entirely dependent on the configuration of twinning in the tetragonal phase. The observations in this study provided useful information for understanding the relationship between the crystallographic domains and the magnetic domains in MnV₂O₄.