16 research outputs found
Buffer influence on magnetic dead layer, critical current and thermal stability in magnetic tunnel junctions with perpendicular magnetic anisotropy
We present a thorough research on Ta/Ru-based buffers and their influence on
features crucial from the point of view of applications of MTJs, such as
critical switching current and thermal stability. We investigate devices
consisting of buffer/FeCoB/MgO/FeCoB/Ta/Ru multilayers for three different
buffers: Ta 5 / Ru 10 / Ta 3, Ta 5 / Ru 10 / Ta 10 and Ta 5 / Ru 20 / Ta 5 (all
thicknesses in nm). In addition, we study systems with a single FeCoB layer
deposited above as well as below the MgO barrier. The crystallographic texture
and the roughness of the buffers are determined by means of XRD and atomic
force microscopy measurements. Furthermore, we examine the magnetic domain
pattern, the magnetic dead layer thickness and the perpendicular magnetic
anisotropy fields for each sample. Finally, we investigate the effect of the
current induced magnetization switching for nanopillar junctions with lateral
dimensions ranging from 1 {\mu}m down to 140 nm. Buffer Ta 5 / Ru 10 / Ta 3,
which has the thickest dead layer, exhibits a large increase in the thermal
stability factor while featuring a slightly lower critical current density
value when compared to the buffer with the thinnest dead layer Ta 5 / Ru 20 /
Ta 5
Study of Spin-Orbit Interactions and Interlayer Ferromagnetic Coupling in Co/Pt/Co Trilayers in Wide Range of Heavy Metal Thickness
The spin-orbit torque, a torque induced by a charge current flowing through
the heavy-metal conducting layer with strong spin-orbit interactions, provides
an efficient way to control the magnetization direction in
heavy-metal/ferromagnet nanostructures, required for applications in the
emergent magnetic technologies like random access memories, high-frequency nano
oscillators, or bio-inspired neuromorphic computations. We study the interface
properties, magnetization dynamics, magnetostatic features and spin-orbit
interactions within the multilayer system
Ti(2)/Co(1)/Pt(0-4)/Co(1)/MgO(2)/Ti(2) (thicknesses in nanometers) patterned by
optical lithography on micrometer-sized bars. In the investigated devices, Pt
is used as a source of the spin current and as a non-magnetic spacer with
variable thickness, which enables the magnitude of the interlayer ferromagnetic
exchange coupling to be effectively tuned. We also find the Pt
thickness-dependent changes in magnetic anisotropies, magnetoresistance,
effective Hall angle and, eventually, spin-orbit torque fields at interfaces.
The experimental findings are supported by the relevant interface
structure-related simulations, micromagnetic, macrospin, as well as the spin
drift-diffusion models. Finally, the contribution of the spin-orbital
Edelstein-Rashba interfacial fields is also briefly discussed in the analysis.Comment: 39 pages, 14 figure
Magnetic Noise Prediction and Evaluation in Tunneling Magnetoresistance Sensors
We propose a simple model for prediction of magnetic noise level in tunneling magnetoresistance (TMR) sensors. The model reproduces experimental magnetic 1/f and white noise components, which are dependent on sensors resistance and field sensitivity. The exact character of this dependence is determined by comparing the results with experimental data using a statistical cross-validation procedure. We show that the model is able to correctly predict magnetic noise level for systems within wide range of resistance, volume and sensitivity, and that it can be used as a robust method for noise evaluation in TMR sensors based on a small number of easily measurable parameters only