Browsing by Author "Grutter, Alexander J."

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    Vertically graded Fe-Ni alloys with low damping and a sizable spin-orbit torque
    Maizel, Rachel E.; Wu, Shuang; Balakrishnan, Purnima P.; Grutter, Alexander J.; Kinane, Christy J.; Caruana, Andrew J.; Nakarmi, Prabandha; Nepal, Bhuwan; Smith, David A.; Lim, Youngmin; Jones, Julia L.; Thomas, Wyatt C.; Zhao, Jing; Michel, F. Marc; Mewes, Tim; Emori, Satoru (American Physical Society, 2024-10-21)
    Energy-efficient spintronic devices require a large spin-orbit torque (SOT) and low damping to excite magnetic precession. In conventional devices with heavy-metal/ferromagnet bilayers, reducing the ferromagnet thickness to approximately 1 nm enhances the SOT but dramatically increases damping. Here, we investigate an alternative approach based on a 10-nm-thick single-layer ferromagnet to attain both low damping and a sizable SOT. Instead of relying on a single interface, we continuously break the bulk inversion symmetry with a vertical compositional gradient of two ferromagnetic elements: Fe with low intrinsic damping and Ni with sizable spin-orbit coupling. We find low effective damping parameters of αeff<5×10-3 in the Fe-Ni alloy films, despite the steep compositional gradients. Moreover, we reveal a sizable antidamping SOT efficiency of |θAD|≈0.05, even without an intentional compositional gradient. Through depth-resolved x-ray diffraction, we identify a lattice strain gradient as crucial symmetry breaking that underpins the SOT. Our findings provide fresh insights into damping and SOTs in single-layer ferromagnets for power-efficient spintronic devices.