Switching field distributions with spin transfer torques in perpendicularly magnetized spin-valve nanopillars

Abstract

We present switching field distributions of spin-transfer-assisted magnetization reversal in perpendicularly magnetized Co/Ni multilayer spin-valve nanopillars at room temperature. Switching field measurements of the Co/Ni free layer of spin-valve nanopillars with a 50 nm × 300 nm ellipse cross section were conducted as a function of current. The validity of a model that assumes a spin-current-dependent effective barrier for thermally activated reversal is tested by measuring switching field distributions under applied direct currents. We show that the switching field distributions deviate significantly from the double exponential shape predicted by the effective barrier model, beginning at applied currents as low as half of the zero field critical current. Barrier heights extracted from switching field distributions for currents below this threshold are a monotonic function of the current. However, the thermally induced switching model breaks down for currents exceeding the critical threshold.

Magnetization switching by current and microwaves

“…Solving Eqs. (19) and (20) with respect to f b and θ d , we found that the frequency determining the boundary between region 1 and region 2 is given by…”

Shape effects on the cluster spreading process of spin-crossover compounds analyzed within an elastic model with Eden and Kawasaki dynamics

“…27,36 Therefore, it is important to study clustering in highly anisotropic shapes, such as ellipses, used also as sample shapes in other magnetic materials, such as nanopillars. 37 Moreover, the study of ellipses is useful as different points on their surface are characterized by different radii of curvature, with the smallest ones at vertices corresponding to the corners of hexagonal/ rectangular systems and the largest ones at co-vertices, approaching infinity for elongated ellipses and then corresponding to linear edges. In addition, the control of the eccentricity of ellipses enables one to study systems with shapes changing from circular to needles.…”

Magnetic Multilayer Structures for Spin Torque Nano Oscillator

“…Moreover, such devices would be able to generate oscillations requiring low or even zero external magnetic fields [13][14][15][16][17]. Given this context, this dissertation is focused on the exploration of innovated magnetic multilayers systems utilizing PMA materials with an ultimate goal to lower the switching current density of STT devices and to create coherent oscillation with output powers larger than 0.5W.…”

“…Moreover, the low damping constant of MnAl (~0.006) [84] is very desirable for low energy dissipation spin torque devices such as spin-transfer torque magnetic tunnel junctions and spin torque nano-oscillators (STNO) [85]. Typically STNO operation requires very large external magnetic fields, however recent innovation utilizing PMA materials has made it possible to operate at low field or even at zero field [13][14][15][16][17].…”

“…By extracting the slope of J C AP-P and comparing with the pre-factor in Eq. (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), we estimate /P = 0.42g(). Given that  = 0.009 and P = 0.4 [177], then g()=0.054, which is almost an order smaller than the expected range between 0.1 and 0.5 [38].…”