11 research outputs found
Large inverse tunneling magnetoresistance in CoCrFeAl/MgO/CoFe magnetic tunnel junctions
Magnetic tunnel junctions with the layer sequence
CoCrFeAl/MgO/CoFe were fabricated by magnetron sputtering
at room temperature (RT). The samples exhibit a large inverse tunneling
magnetoresistance (TMR) effect of up to -66% at RT. The largest value of -84%
at 20 K reflects a rather weak influence of temperature. The dependence on the
voltage drop shows an unusual behavior with two almost symmetric peaks at
mV with large inverse TMR ratios and small positive values around zero
bias
Structural and magneto-transport characterization of Co_2Cr_xFe_(1-x)Al Heusler alloy films
We investigate the structure and magneto-transport properties of thin films
of the Co_2Cr_xFe_(1-x)Al full-Heusler compound, which is predicted to be a
half-metal by first-principles theoretical calculations. Thin films are
deposited by magnetron sputtering at room temperature on various substrates in
order to tune the growth from polycrystalline on thermally oxidized Si
substrates to highly textured and even epitaxial on MgO(001) substrates,
respectively. Our Heusler films are magnetically very soft and ferromagnetic
with Curie temperatures up to 630 K. The total magnetic moment is reduced
compared to the theoretical bulk value, but still comparable to values reported
for films grown at elevated temperature. Polycrystalline Heusler films combined
with MgO barriers are incorporated into magnetic tunnel junctions and yield 37%
magnetoresistance at room temperature
Magnetization dynamics in spin torque nano-oscillators: Vortex state versus uniform state
Lehndorff R, Buergler DE, Gliga S, et al. Magnetization dynamics in spin torque nano-oscillators: Vortex state versus uniform state. PHYSICAL REVIEW B. 2009;80(5): 054412.Current-driven magnetization dynamics in spin torque nano-oscillators (STNOs) is intensely investigated because of its high potential for high-frequency (HF) applications. We experimentally study current-driven HF excitations of STNOs for two fundamental magnetization states of the free layer, namely, vortex state and uniform in-plane magnetization. Our ability to switch between the two states in a given STNO enables a direct comparison of the critical currents, agility, power, and linewidth of the HF output signals. We find that the vortex state has some superior properties, in particular, it maximizes the emitted HF power and shows a wider frequency tuning range at a fixed magnetic field