arXiv subjects

Rachel E. Maizel

Publications and source records attributed to Rachel E. Maizel.

3 recordsLinked to original sources

arXiv2026

Enabling high giant magnetoresistance in simple spin valves with ultrathin seed and free layers

Emerging spin-orbit-torque devices based on spin valves require a thin magnetic free layer to maximize the torque per moment. However, reducing the free-layer thickness to $\lesssim 2$ nm deteriorates the giant magnetoresistance (GMR) signal for electrical readout. Here, we demonstrate that the addition of a 1-nm Cu seed layer promotes sharp interfaces in simple polycrystalline Co-based spin valves, enabling high GMR ratios of 5-7% at sub-2-nm free-layer thicknesses. Our work offers a pathway for engineering high-signal GMR readout in spin-orbit-torque digital memories and neuromorphic computers.

cond-mat.mtrl-sci↗

arXiv2025

Absence of detectable spin and orbital pumping from Ni to Nb by out-of-plane ferromagnetic resonance

Excited ferromagnets can pump spin angular momentum, along with possibly orbital angular momentum. Among elemental ferromagnets, Ni has been proposed to exhibit substantial orbital pumping relative to spin pumping. Here, we search for a signature of orbital pumping by Ni, specifically by comparing out-of-plane ferromagnetic resonance in heterostructures without Ni (FeV/Nb) and with Ni (FeV-Ni/Nb). The FeV/Nb series shows a clear increase in Gilbert damping with the Nb sink thickness, attributed to spin pumping from FeV to Nb. Surprisingly, the FeV-Ni/Nb series exhibits no such damping increase, revealing no significant spin or orbital pumping from Ni to Nb. Our results offer a fresh perspective on angular-momentum transfer in Ni-based heterostructures, suggesting that the interpretation of some strong orbitronic effects may require further consideration.

cond-mat.mes-hall↗

arXiv2024

Vertically Graded Fe-Ni Alloys with Low Damping and a Sizeable Spin-Orbit Torque

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 $\sim$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 $α_\mathrm{eff} < 5\times10^{-3}$ in the FeNi alloy films, despite the steep compositional gradients. Moreover, we reveal a sizable anti-damping SOT efficiency of $|θ_\mathrm{DL}| \approx 0.05$, 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.

cond-mat.mtrl-sci↗