783 research outputs found
Magnetic-history-dependent nanostructural and resistivity changes in Pr0.5Ca0.5Mn0.98Cr0.02O3
We show that nanostructure and resistivity of Pr0.5Ca0.5Mn0.98Cr0.02O3 are
sensitive to whether the sample is zero-field-cooled (ZFC) of field-cooled (FC)
either in the 'self magnetic field (H = 2 T)' of the electron microscope or
under the external magnetic field of 2 T. FC resistivity at H = 2 T is lower
than ZFC values below 140 K. The average value of the chare-orbital modulation
vector (q = 0.44) of the FC crystallites is lower than that of the ZFC
cystallites (q = 0.48) and the FC crystallites exhibit numerous defects like
discommensuration, dislocations and regios with loss of superstructures
compared to the ZFC crystallites.Comment: 7 pages, 3 figure
Structure determination of a brownmillerite Ca2Co2O5 thin film by Precession Electron Diffraction
Calcium cobaltite thin films with a ratio Ca/Co=1 were grown on (101)-NdGaO3
substrate by the pulsed laser deposition technique. The structure of the
deposited metastable phase is solved using a precession electron diffraction 3D
dataset recorded from a cross-sectional sample. It is shown that an ordered
oxygen-deficient Ca2Co2O5+d perovskite of the brownmillerite-type with lattice
parameters a= 0.546nm, b=1.488nm and c=0.546nm (SG: Ibm2) has been stabilized
using the substrate induced strain. The structure and microstructure of this
metastable cobaltite is further discussed and compared to related bulk
materials based on our transmission electron microscopy investigationsComment: 13 pages, 10 figures, 2 tables, accepted in Phys. Rev.
Rhodium Doped Manganites : Ferromagnetism and Metallicity
The possibility to induce ferromagnetism and insulator to metal transitions
in small A site cation manganites Ln_{1-x}Ca_xMnO_3 by rhodium doping is shown
for the first time. Colossal magnetoresistance (CMR) properties are evidenced
for a large compositional range (0.35 \leq x < 0.60). The ability of rhodium to
induce such properties is compared to the results obtained by chromium and
ruthenium doping. Models are proposed to explain this behavior.Comment: 11 pages, 8 figure
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