963 research outputs found
Proximity-induced density-of-states oscillations in a superconductor/strong-ferromagnet system
We have measured the evolution of the tunneling density of states (DOS) in
superconductor/ferromagnet (S/F) bilayers with increasing F-layer thickness,
where F in our experiment is the strong ferromagnet Ni. As a function of
increasing Ni thickness, we detect multiple oscillations in the DOS at the
Fermi energy from differential conductance measurements. The features in the
DOS associated with the proximity effect change from normal to inverted twice
as the Ni thickness increases from 1 to 5 nm.Comment: 4 pages, 4 figure
Switching Current vs. Magnetoresistance in Magnetic Multilayer Nanopillars
We study current-driven magnetization switching in nanofabricated magnetic
trilayers, varying the magnetoresistance in three different ways. First, we
insert a strongly spin-scattering layer between the magnetic trilayer and one
of the electrodes, giving increased magnetoresistance. Second, we insert a
spacer with a short spin-diffusion length between the magnetic layers,
decreasing the magnetoresistance. Third, we vary the angle between layer
magnetizations. In all cases, we find an approximately linear dependence
between magnetoresistance and inverse switching current. We give a qualitative
explanation for the observed behaviors, and suggest some ways in which the
switching currents may be reduced.Comment: 3 pages, 4 figure
Measurement of spin memory lengths in PdNi and PdFe ferromagnetic alloys
Weakly ferromagnetic alloys are being used by several groups in the study of
superconducting/ferromagnetic hybrid systems. Because spin-flip and spin-orbit
scattering in such alloys disrupt the penetration of pair correlations into the
ferromagnetic material, it is desirable to have a direct measurement of the
spin memory length in such alloys. We have measured the spin memory length at
4.2 K in sputtered Pd0.88Ni0.12 and Pd0.987Fe0.013 alloys using methods based
on current-perpendicular-to-plane giant magnetoresistance. The alloys are
incorporated into hybrid spin valves of various types, and the spin memory
length is determined by fits of the Valet-Fert spin-transport equations to data
of magnetoresistance vs. alloy thickness. For the case of PdNi alloy, the
resulting values of the spin memory length are lsf(PdNi) = 2.8 +/- 0.5 nm and
5.4 +/- 0.6 nm, depending on whether or not the PdNi is exchange biased by an
adjacent Permalloy layer. For PdFe, the spin memory length is somewhat longer,
lsf(PdFe) = 9.6 +/- 2 nm, consistent with earlier measurements indicating lower
spin-orbit scattering in that material. Unfortunately, even the longer spin
memory length in PdFe may not be long enough to facilitate observation of
spin-triplet superconducting correlations predicted to occur in
superconducting/ferromagnetic hybrid systems in the presence of magnetic
inhomogeneity.Comment: 7 pages, 8 figure
Manipulating Current-Induced Magnetization Switching
We summarize our recent findings on how current-driven magnetization
switching and magnetoresistance in nanofabricated magnetic multilayers are
affected by varying the spin-scattering properties of the non-magnetic spacers,
the relative orientations of the magnetic layers, and spin-dependent scattering
properties of the interfaces and the bulk of the magnetic layers. We show how
our data are explained in terms of current-dependent effective magnetic
temperature.Comment: 6 pages, 6 figures, submitted to MMM'04 proceeding
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