165 research outputs found
Effects of impurity atoms on sputtered GMR multilayers
We have investigated the effects of residual
gas impurity atoms on interlayer exchange coupling
and giant magnetoresistance (GMR) in Co(9Ä)/Cu(9Ä)
multilayers. Structural analysis was performed by Co(59)
NMR. We deposited sub-monolayer quantities of residual
gases at different points in the Co/Cu bilayer; the
interfaces, or the middle of the Cu spacers or CO magnetic
layers. Impurities at the interface lower the GMR
and increase remenant fraction and saturation field. We
are able to model these results phenomenologically by
adding biquadratic coupling. Impurities in the bulk of
the Cu layers lower GMR still further, and such samples
are well described by models containing almost
100% biquadratic coupling. We have demonstrated that
the ttansport parameters in our samples are largely
unaffected by small quantities of impurities, but that
the interlayer coupling is extremely sensitive to them,
particularly in the bulk of the Cu spacer layers
Reply on the comment on the paper "Superconducting transition in Nb nanowires fabricated using focused ion beam"
In this communication we present our response to the recent comment of A.
Engel regarding our paper on FIB- fabricated Nb nanowires (see Vol. 20 (2009)
Pag. 465302). After further analysis and additional experimental evidence, we
conclude that our interpretation of the experimental results in light of QPS
theory is still valid when compared with the alternative proximity-based model
as proposed by A. Engel.Comment: 3 pages, 1 figure, accepted by Nanotechnolog
Controlled enhancement or suppression of exchange biasing using impurity -layers
The effects of inserting impurity -layers of various elements into a
Co/IrMn exchange biased bilayer, at both the interface, and at given points
within the IrMn layer a distance from the interface, has been investigated.
Depending on the chemical species of dopant, and its position, we found that
the exchange biasing can be either strongly enhanced or suppressed. We show
that biasing is enhanced with a dusting of certain magnetic impurities, present
at either at the interface or sufficiently far away from the Co/IrMn interface.
This illustrates that the final spin structure at the Co/IrMn interface is not
only governed by interface structure/roughness but is also mediated by local
exchange or anisotropy variations within the bulk of the IrMn
Scattering in InAs/GaSb Coupled Quantum Wells as a Probe of Higher Order Subband Hybridisation
We have performed a detailed investigation into the inter-subband scattering within InAs/GaSb coupled quantum wells in the electron dominated regime. By considering the carrier mobilities and the quantum lifetime as a function of carrier density, we find that the occupation of higher order electron-like subbands are inhibited by anticrossing with the hole subbands. We also find that, by applying a gate bias to the GaSb layer, we are able to move the electron-hole anticrossing point in energy, modulating the electron-like states that should be localised within the InAs layer
Exchange anisotropy pinning of a standing spin wave mode
Standing spin waves in a thin film are used as sensitive probes of interface
pinning induced by an antiferromagnet through exchange anisotropy. Using
coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin
wave thickness mode in Ni(80)Fe(20)/Ir(25)Mn(75) exchange biased bilayers was
studied for a range of IrMn thicknesses. We show that pinning of the standing
mode can be used to amplify, relative to the fundamental resonance, frequency
shifts associated with exchange bias. The shifts provide a unique `fingerprint'
of the exchange bias and can be interpreted in terms of an effective
ferromagnetic film thickness and ferromagnet/antiferromagnet interface
anisotropy. Thermal effects are studied for ultra-thin antiferromagnetic
Ir(25)Mn(75) thicknesses, and the onset of bias is correlated with changes in
the pinning fields. The pinning strength magnitude is found to grow with
cooling of the sample, while the effective ferromagnetic film thickness
simultaneously decreases. These results suggest that exchange bias involves
some deformation of magnetic order in the interface region.Comment: 7 pages, 7 figure
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