10 research outputs found
Uncompensated magnetization and exchange-bias field in LaSrMnO/YMnO bilayers: The influence of the ferromagnetic layer
We studied the magnetic behavior of bilayers of multiferroic and nominally
antiferromagnetic o-YMnO (375~nm thick) and ferromagnetic
LaSrMnO and LaCaMnO (nm), in particular the vertical magnetization shift and exchange
bias field for different thickness and magnetic dilution of the
ferromagnetic layer at different temperatures and cooling fields. We have found
very large shifts equivalent to up to 100\% of the saturation value of
the o-YMO layer alone. The overall behavior indicates that the properties of
the ferromagnetic layer contribute substantially to the shift and that
this does not correlate straightforwardly with the measured exchange bias field
.Comment: 10 figures, 8 page
Revealing the origin of the vertical hysteresis loop shifts in an exchange biased Co/YMnO bilayer
We have investigated exchange bias effects in bilayers composed by the
antiferromagnetic o-YMnO and ferromagnetic Co thin film by means of SQUID
magnetometry, magnetoresistance, anisotropic magnetoresistance and planar Hall
effect. The magnetization and magnetotransport properties show pronounced
asymmetries in the field and magnetization axes of the field hysteresis loops.
Both exchange bias parameters, the exchange bias field as well as
the magnetization shift , vanish around the N\'eel temperature K. We show that the magnetization shift is also measured by
a shift in the anisotropic magnetoresistance and planar Hall resistance having
those a similar temperature dependence as the one obtained from magnetization
measurements. Because the o-YMnO film is highly insulating, our results
demonstrate that the shift originates at the interface within the
ferromagnetic Co layer. To show that the main results obtained are general and
not because of some special characteristics of the o-YMO layer, similar
measurements were done in Co/CoO micro-wires. The transport and magnetization
characterization of the micro-wires supports the main conclusion that these
effects are related to the response of the ferromagnetic Co layer at the
interface.Comment: 16 Figures, in press at J. Phys.: Condensed Matter 201
Study of the Negative Magneto-Resistance of Single Proton-Implanted Lithium-Doped ZnO Microwires
The magneto-transport properties of single proton-implanted ZnO and of
Li(7\%)-doped ZnO microwires have been studied. The as-grown microwires were
highly insulating and not magnetic. After proton implantation the Li(7\%) doped
ZnO microwires showed a non monotonous behavior of the negative
magneto-resistance (MR) at temperature above 150 K. This is in contrast to the
monotonous NMR observed below 50 K for proton-implanted ZnO. The observed
difference in the transport properties of the wires is related to the amount of
stable Zn vacancies created at the near surface region by the proton
implantation and Li doping. The magnetic field dependence of the resistance
might be explained by the formation of a magnetic/non magnetic heterostructure
in the wire after proton implantation.Comment: 6 pages with 5 figure
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