Electrical manipulation of magnetization switching in Co2FeAl alloy based magnetic tunnel junctions with in-plane and perpendicular magnetization
Electrical manipulation of magnetization switching, such as spin-transfer torque (STT) switching, electric-field-assistant magnetization switching, and spin-orbit torque (SOT) switching, has been attracting great attentions due to its applications in low-power-consumption spintronic devices, such as magnetoresistive random access memories (MRAMs) and non-volatile magnetic-logic circuits. Recent investigations of electrical manipulation of magnetization switching in magnetic tunnel junctions (MTJs) have mainly been carried out in CoFeB/MgO/CoFeB structures. However, the switching current density of those MTJs is still too high for the scaling of gigabit MRAMs. Therefore, the establishment of new ferromagnetic materials for MTJs is greatly desired.
Spin-transfer switching in full-Heusler Co2FeAl-based magnetic tunnel junctions
We demonstrated spin-transfer magnetization switching using magnetic tunnel junctions (MTJs) with a full-Heusler alloy Co2FeAl (CFA). We prepared CFA (1.5 nm)/MgO/CoFe (4 nm) (“CFA-free”) and CFA (30 nm)/MgO/CoFeB (2 nm) (“CFA-reference”) MTJs on a Cr(001) layer. The intrinsic critical current density (Jc0) of the CFA-free (CFA-reference) MTJ was 29 MA/cm2 (7.1 MA/cm2). The larger Jc0 of the CFA-free MTJ is attributed to the significant enhancement of the Gilbert damping factor (∼0.04) of the CFA due to the Cr layer. The Jc0 of the CFA-reference is as small as that reported for typical CoFeB/MgO/CoFeB MTJs.
The fragmentation of small asteroids in the atmosphere
The fragmentation of a small asteroid in the atmosphere greatly increases its cross-sections for aerodynamic braking and energy dissipation. The differential pressure across a meteoroid disperses its fragments at a velocity that increases with atmospheric density and impact velocity and decreases with meteoroid density. At a typical impact velocity of 22 km/s, the atmosphere absorbs more than half the kinetic energy of stony meteoroids with diameters, D M < 220 M AND IRON METEOROIDS WITH D M < 80 m. The corresponding diameter for comets with impact velocity 50 km/s is D M < 1600 m. Most of this energy dissipation occurs in a fraction of a scale height, which causes large meteoroids to appear to »explode« or »flare« at the end of their visible paths