Individual disk-shaped Co-Fe-B nanodots are driven into a superparamagnetic state by a spin-transfer torque, and their time-dependent magnetoresistance fluctuations are measured as a function of current. A thin layer of oxidation at the edges has a dramatic effect on the magnetization dynamics. A combination of experimental results and atomistic spin simulations shows that pinning to oxide grains can reduce the likelihood that fluctuations lead to reversal, and can even change the easy-axis direction. Exchange-bias loop shifts and training effects are observed even at room temperature after brief exposure to small fields. The results have implications for studies of core-shell nanoparticles and small magnetic tunnel junctions and spin-torque oscillators.
Magnetization switching utilizing the spin orbit torque of heavy metals is a promising alternative to spin transfer torque for a faster and more energy efficient write mechanism for magnetic random-access memory. We report spin orbit torque switching in a 20 nm diameter, CoFeB-MgO-based perpendicular magnetic tunnel junctions with a thermal stability factor of ~47. Conductive atomic force microscopy was used to measure the tunnel magnetoresistance before and after current pulses through the heavy metal underlayer, and magnetostatic shifts in the minor loops provided evidence of spin orbit torque switching. Comparison of estimated critical current densities and write energies suggest that spin orbit torque can be used as an effective switching mechanism for small and thermally stable perpendicular magnetic tunnel junctions.
I.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.