580 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
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
Gallium Substituted "114" YBaFe4O7: From a ferrimagnetic cluster glass to a cationic disordered spin glass
The study of the ferrites YBaFe4-xGaxO7 shows that the substitution of Ga for
Fe in YBaFe4O7 stabilizes the hexagonal symmetry for 0.40 < x < 0.70, at the
expense of the cubic one. Using combined measurements of a. c. and d. c.
magnetization, we establish that Ga substitution for Fe in YBaFe4O7 leads to an
evolution from a geometrically frustrated spin glass (for x = 0) to a cationic
disorder induced spin glass (x = 0.70). We also find an intermediate narrow
range of doping where the samples are clearly phase separated having small
ferrimagnetic clusters embedded in a spin glass matrix. The origin of the
ferrimagnetic clusters lies in the change in symmetry of the samples from cubic
to hexagonal (and a consequent lifting of the geometrical frustration) as a
result of Ga doping. We also show the presence of exchange bias and domain wall
pinning in these samples. The cause of both these effects can be traced back to
the inherent phase separation present in the samples.Comment: 25 pages, 10 figure
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