17 research outputs found
Origin of training effect of exchange bias in Co/CoO due to irreversible thermoremanent magnetization of the magnetically diluted antiferromagnet
The irreversible thermoremanent magnetization of a sole, magnetically diluted
epitaxial antiferromagnetic CoO(100) layer is determined by the mean of
its thermoremanent magnetizations at positive and negative remanence. During
hysteresis-loop field cycling, thermoremanent magnetization exhibits successive
reductions, consistent with the training effect (TE) of the exchange bias
measured for the corresponding CoO(100)/Co bilayer. The TE of exchange
bias is shown to have its microscopic origin in the TE of the irreversible
thermoremanent magnetization of the magnetically diluted AFM
Exchange Bias in BiFe_{0.8}Mn_{0.2}O_3 Nanoparticles with an Antiferromagnetic Core and a Diluted Antiferromagnetic Shell
We have observed conventional signature of exchange bias (EB), in form of
shift in field-cooled (FC) hysteresis loop, and training effect, in
BiFe0.8Mn0.2O3 nanoparticles. From neutron diffraction, thermoremanent
magnetization and isothermoremanent magnetization measurements, the
nanoparticles are found to be core-shell in nature, consisting of an
antiferromagnetic (AFM) core, and a 2-dimensional diluted AFM (DAFF) shell with
a net magnetization under a field. The analysis of the training effect data
using the Binek's model shows that the observed loop shift arises entirely due
to an interface exchange coupling between core and shell, and the intrinsic
contribution of the DAFF shell to the total loop shift is zero. A significantly
high value of EB field has been observed at room temperature. The present study
is useful to understand the origin of EB in other DAFF-based systems as well.Comment: 20 pages, 7 figures, Phys. Rev. B 2011 (accepted
Complex ferromagnetic state and magnetocaloric effect in single crystalline Nd_{0.7}Sr_{0.3}MnO_{3}
The magnetocaloric effect in single crystalline Nd_{0.7}Sr_{0.3}MnO_{3} is
investigated by measuring the field-induced adiabatic change in temperature
which reveals a single negative peak around 130 K well below the Curie
temperature (T_C=203 K). In order to understand this unusual magnetocaloric
effect, we invoke the reported {55}^Mn spin-echo nuclear magnetic resonance,
electron magnetic resonance and polarized Raman scattering measurements on
Nd_{0.7}Sr_{0.3}MnO_{3}. We show that this effect is a manifestation of a
competition between the double exchange mechanism and correlations arising from
coupled spin and lattice degrees of freedom which results in a complex
ferromagnetic state. The critical behavior of Nd_{0.7}Sr_{0.3}MnO_{3} near
Curie temperature is investigated to study the influence of the coupled degrees
of freedom. We find a complicated behavior at low fields in which the order of
the transition could not be fixed and a second-order-like behavior at high
fields.Comment: Accepted for publication in Phys. Rev.
Hysteretic giant magnetoimpedance effect analyzed by first-order reversal curves
Hysteretic giant magnetoimpedance (GMI) of amorphous ribbons with a
well-defined transversal domain structure is investigated by means of
first-order reversal curves (FORC) analysis. The FORCs are not confined to the
hysteretic area, exceeding the major curve amplitude. Irreversible switches of
the transverse permeability, caused by domain wall structure transitions, may
be the origin of the observed FORC distribution. An interlinked
hysteron/anti-hysteron model is proposed to interpret it, which allows
analyzing the influence of frequency and magnetostriction upon the hysteretic
GMI effect.Comment: 19 pages, 9 figure