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AM: Magnetismus
AM 11: Postersitzung
AM 11.58: Poster
Dienstag, 24. März 1998, 16:15–20:00, B
Investigation of Physical Properties of CMR Perovskite Manganates — •Y. Xu, A. Müller, A. Drechsler, V. Dworak, W. Guan, and U. Hartmann — Experimentalphysik, Universität des Saarlandes, D-66041 Saarbrücken
We have successfully prepared the perovskite manganates
La0.67Ca0.33MnO3,
La0.67Ba0.33MnO3,
and La0.67Sr0.33MnO3. XRD revealed all samples being single perovskite phase.
Magnetization
measurements show that all samples are ferromagnetic with high Curie temperature close to
room-temperature.
Magnetoresistance
values were deduced from resistivity measurements at various magnetic
fields up to 8 T.
The grain size ranges from a few ten
nm to a few µm demonstrated by SEM. Polishing the sample surface creates some relatively
flat areas of ∼ µm on the crystals. This offers the possibility of local
MFM investigations. With
a magnetic CoCrPt tip even without an external field, the magnetic image contrast is very clear
below TC. Under a field of 23 mT parallel and 45 mT perpendicular to the surface of
La0.67Sr0.33MnO3 sample, the magnetic image contrast increases considerably.
Similar results
were obtained for La0.67Ba0.33MnO3. However, for La0.67Ca0.33MnO3
at room temperature
(above TC) there is no contrast in the magnetic image in zero field and
even under a field of up to 50
mT. Our measurements in particular show the possibility to study the magnetic structure in the
crystals by MFM.