Magnetoresistance Dynamics in Superparamagnetic Co-Fe- B Nanodots

Brad Parks, Ahmed Abdelgawad, Thomas Wong, Richard F.L. Evans, Sara A. Majetich

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Article number014063
JournalPhysical Review Applied
Issue number1
Publication statusPublished - 30 Jan 2020

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