Browsing by Author "Maizel, Rachel E."

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    Quantifying the orbital-to-spin moment ratio under dynamic excitation
    Emori, Satoru; Maizel, Rachel E.; Street, Galen T.; Jones, Julia L.; Arena, Dario A.; Shafer, Padraic; Klewe, Christoph (AIP Publishing, 2024-03-18)
    The orbital component of magnetization dynamics, e.g., excited by ferromagnetic resonance (FMR), may generate “orbitronic” effects in nanomagnetic devices. Yet, distinguishing orbital dynamics from spin dynamics remains a challenge. Here, we employ x-ray magnetic circular dichroism (XMCD) to quantify the ratio between the orbital and spin components of FMR-induced dynamics in a Ni80Fe20 film. By applying the XMCD sum rules at the Ni L 3 , 2 edges, we obtain an orbital-to-spin ratio of 0.108 ± 0.005 for the dynamic magnetization. This value is consistent with 0.102 ± 0.008 for the static magnetization, probed with the same x-ray beam configuration as the dynamic XMCD experiment. The demonstrated method presents a possible path to disentangle orbitronic effects from their spintronic counterparts in magnetic media.
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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.