479 research outputs found
Magnetocapacitance effect in perovskite-superlattice based multiferroics
We report the structural and magnetoelectrical properties of
LaCaMnO/BaTiO perovskite superlattices grown on
(001)-oriented SrTiO by the pulsed laser deposition technique. Magnetic
hysteresis loops together with temperature dependent magnetic properties
exhibit well-defined coercivity and magnetic transition temperature (T)
\symbol{126}140 K. electrical studies of films show that the
magnetoresistance (MR) is dependent on the BaTiO thickness and negative
as high as 30% at 100K are observed. The electrical studies reveal
that the impedance and capacitance in these films vary with the applied
magnetic field due to the magnetoelectrical coupling in these structures - a
key feature of multiferroics. A negative magnetocapacitance value in the film
as high as 3% per tesla at 1kHz and 100K is demonstrated, opening the route for
designing novel functional materials.Comment: To be published in Applied Physics Letter
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
Effect of ferroelectric layers on the magnetocapacitance properties of superlattices-based oxide multiferroics
A series of superlattices composed of ferromagnetic
LaCaMnO (LCMO) and ferroelectric/paraelectric
BaSrTiO (0x1) were deposited on SrTiO
substrates using the pulsed laser deposition. Films of epitaxial nature
comprised of spherical mounds having uniform size are obtained.
Magnetotransport properties of the films reveal a ferromagnetic Curie
temperature in the range of 145-158 K and negative magnetoresistance as high as
30%, depending on the type of ferroelectric layers employed for their growth
(\QTR{it}{i.e.} '\QTR{it}{x'} value). Ferroelectricity at temperatures ranging
from 55 K to 105 K is also observed, depending on the barium content. More
importantly, the multiferroic nature of the film is determined by the
appearance of negative magnetocapacitance, which was found to be maximum around
the ferroelectric transition temperature (3% per \QTR{it}{tesla}). These
results are understood based on the role of the ferroelectric/paraelectric
layers and strains in inducing the multiferroism.Comment: Accepted to Applied Physics Letter
The role of ferroelectric-ferromagnetic layers on the properties of superlattice-based multiferroics
A series of superlattices and trilayers composed of ferromagnetic and
ferroelectric or paraelectric layers were grown on (100) SrTiO3 by the pulsed
laser deposition technique. Their structural and magneto-electric properties
were examined. The superlattices made of ferromagnetic Pr0.85Ca0.15MnO3 (PCMO)
and a ferroelectric, namely Ba0.6Sr0.4TiO3 (BST) or BaTiO3, showed enhanced
magnetoresistance (MR) at high applied magnetic field, whereas such enhancement
was absent in Pr0.85Ca0.15MnO3/SrTiO3 superlattices, which clearly demonstrates
the preponderant role of the ferroelectric layers in this enhanced MR.
Furthermore, the absence of enhanced MR in trilayers of PCMO/BST indicates that
the magneto-electric coupling which is responsible for MR in these systems is
stronger in multilayers than in their trilayer counterparts.Comment: to be published in J. Appl. Phy
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
Correlation between structure and properties in multiferroic LaCaMnO/BaTiO superlattices
Superlattices composed of ferromagnetics, namely LaCaMnO
(LCMO), and ferroelectrics, namely, BaTiO(BTO) were grown on SrTiO at
720C by pulsed laser deposition process. While the out-of-plane lattice
parameters of the superlattices, as extracted from the X-ray diffraction
studies, were found to be dependent on the BTO layer thickness, the in-plane
lattice parameter is almost constant. The evolution of the strains, their
nature, and their distribution in the samples, were examined by the
conventional sin method. The effects of structural variation on the
physical properties, as well as the possible role of the strain on inducing the
multiferroism in the superlattices, have also been discussed.Comment: To be published in Journal of Applied Physic
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