Yui Ishii

Foucault imaging and small-angle electron diffraction in controlled external magnetic fields.

We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La0.7Sr0.3MnO3 (LSMO) and Nd0.5Sr0.5MnO3, in order to visualize magnetic domains and their magnetic responses to external magnetic fields. In rhombohedral-structured LSMO, pinning of magnetic domain walls at crystallographic twin boundaries was found to have a strong influence on the generation of new magnetic domains in external applied magnetic fields.

Lorentz microscopy and small-angle electron diffraction study of magnetic textures in L a 1 − x S r x Mn O 3 ( 0.15 x 0.30 ) : The role of magnetic anisotropy

Magnetic textures in the ferromagnetic phases of

Structural Phase Transition and Microstructures in Stuffed Tridymite-Type Compounds; Ba(Al, Fe)2O4

\mathrm{L}{\mathrm{a}}_{1\ensuremath{-}x}\mathrm{S}{\mathrm{r}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}

Formation mechanisms of magnetic bubbles in an M -type hexaferrite: Role of chirality reversal at domain walls

for

Structural changes and microstructures in stuffed tridymite-type compounds Ba1−xSrxAl2O4

0.15lxl0.30

A Fluctuating State in the Framework Compounds (Ba,Sr)Al2O4

have been investigated by Lorentz microscopy combined with small-angle electron diffraction experiments. Various types of magnetic textures characterized by stripe, plate-shaped, and cylindrical (magnetic bubble) domains were found. Two distinct types of magnetic stripe domains appeared in the orthorhombic structure with an inversion symmetry of

Modulated structures and associated microstructures in the ferroelectric phase of Ba1−xSrxAl2O4 for 0.7 ≤ x ≤ 1.0

\mathrm{L}{\mathrm{a}}_{0.825}\mathrm{S}{\mathrm{r}}_{0.175}\mathrm{Mn}{\mathrm{O}}_{3}

Observation of spin textures in La1−xSrxMnO3 (x = 0.175)

, depending significantly on magnetocrystalline anisotropy. Based on in situ observations as functions of temperature and the strength of the external magnetic field, a magnetic field-temperature phase diagram was constructed, showing the stabilization of magnetic bubbles in the ferromagnetic phase of

Field-temperature phase diagram of magnetic bubbles spanning charge/orbital ordered and metallic phases in La1−xSrxMnO3(x=0.125)

\mathrm{L}{\mathrm{a}}_{0.825}\mathrm{S}{\mathrm{r}}_{0.175}\mathrm{Mn}{\mathrm{O}}_{3}

Giant thermal vibrations in the framework compounds Ba1-xSrxAl2O4

.