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Spin-transfer devices that incorporate a polarizer with its magnetization orthogonal to a switchable (free) layer
offer the potential for ultra-fast switching, low power consumption and reliable operation. The non-collinear
magnetizations lead to large initial spin-transfer torques, eliminating the incubation delay seen in devices with
collinear magnetization. Here we present the basic electrical and magnetic characteristics of spin-valve nanopillars
that incorporate a perpendicularly magnetized polarizer and demonstrate current-induced switching with
short current pulses, down to 100 ps in duration. We have fabricated devices that have a CoNi polarizer with
perpendicular magnetization and an in-plane magnetized 3 nm thick Co free layer and a 12 nm thick Co reference
layer, each separated by thin (~ 10 nm) Cu layers. The magnetization of the reference layer is collinear with that
of free layer to read out the device state. The reference layer also contributes to the spin-accumulation acting on
the free layer and leads to a spin-torque that favors the parallel (P) or antiparallel (AP) state depending on the
current pulse polarity, reducing the requirement of precise pulse timing in precessional reversal. The anisotropy
field of the perpendicular polarizer is 1.3 T, i.e. it is high enough so that in-plane fields (< 0.3 T) applied to
switch the magnetizations of the reference and free layers do not reorient the polarizer. Our typical nanopillar
device lateral dimensions are between 60 nm and 300 nm and nanopillars are positioned on coplanar waveguides
to allow for broadband electrical connections and studies with fast rise time pulses, generated by an arbitrary
waveform generator. The switching probability has been determined for variable pulse amplitude and duration,
from 0.1 to 10 ns at room temperature.
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