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Sidewall oxide effects on spin-torque- and magnetic-field-induced reversal characteristics of thin-film nanomagnets


The successful operation of spin-based data storage devices depends on thermally stable magnetic bits. At the same time, the data-processing speeds required by today’s technology necessitate ultrafast switching in storage devices. Achieving both thermal stability and fast switching requires controlling the effective damping in magnetic nanoparticles. By carrying out a surface chemical analysis, we show that through exposure to ambient oxygen during processing, a nanomagnet can develop an antiferromagnetic sidewall oxide layer that has detrimental effects, which include a reduction in the thermal stability at room temperature and anomalously high magnetic damping at low temperatures. The in situ deposition of a thin Al metal layer, oxidized to completion in air, greatly reduces or eliminates these problems. This implies that the effective damping and the thermal stability of a nanomagnet can be tuned, leading to a variety of potential applications in spintronic devices such as spin-torque oscillators and patterned media.

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Figure 1: Cross-sectional view of a nanopillar spin-valve device.
Figure 2: Spin-torque switching and magnetic-field-induced switching characteristics of an Al-passivated device.
Figure 3: Temperature dependence of coercivity and spin-torque switching currents.
Figure 4: Spin-torque phase diagrams measured at 4.2 K.


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We thank J. C. Sankey for providing us with the macrospin simulation code and T. Hauet for helpful discussions. This work was supported in part by the Semiconductor Research Corporation, the Office of Naval Research, the NSF/NSEC program through the Cornell Center for Nanoscale Systems and an IBM-Faculty Partnership award. The work was carried out in part at the Cornell NanoScale Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (Grant ECS 03-35765), and it benefited from use of the facilities of the Cornell Center for Materials Research, which is supported by the NSF/MRSEC program.

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Ozatay, O., Gowtham, P., Tan, K. et al. Sidewall oxide effects on spin-torque- and magnetic-field-induced reversal characteristics of thin-film nanomagnets. Nature Mater 7, 567–573 (2008).

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