0000000000222143
AUTHOR
Christopher H. Marrows
showing 4 related works from this author
Spin orbit torque switching in Ta/CoFeB/MgO without longitudinal fields
2015
Intense investigations are carried out on novel magnetic materials systems with perpendicular magnetic anisotropy (PMA), where new spin-orbit effects occur due to structural inversion asymmetry (SIA). So called spin-orbit torques (SOTs), have been observed for the first time in PMA nano-structures with SIA, when an electric current is injected [1-3], leading to ultra-efficient current-induced domain wall motion and current-induced magnetization switching [2,3].
Spin-orbit torque-driven magnetization switching and thermal effects studied in Ta\CoFeB\MgO nanowires
2014
We demonstrate magnetization switching in out-of-plane magnetized Ta\CoFeB\MgO nanowires by current pulse injection along the nanowires, both with and without a constant and uniform magnetic field collinear to the current direction. We deduce that an effective torque arising from spin-orbit effects in the multilayer drives the switching mechanism. While the generation of a component of the magnetization along the current direction is crucial for the switching to occur, we observe that even without a longitudinal field thermally generated magnetization fluctuations can lead to switching. Analysis using a generalized N\'eel-Brown model enables key parameters of the thermally induced spin-orbi…
Role of B diffusion in the interfacial Dzyaloshinskii-Moriya interaction inTa/Co20Fe60B20/MgOnanowires
2015
We report on current-induced domain wall motion in $\mathrm{Ta}/\mathrm{C}{\mathrm{o}}_{20}\mathrm{F}{\mathrm{e}}_{60}{\mathrm{B}}_{20}/\mathrm{MgO}$ nanowires. Domain walls are observed to move against the electron flow when no magnetic field is applied, while a field along the nanowires strongly affects the domain wall motion velocity. A symmetric effect is observed for up-down and down-up domain walls. This indicates the presence of right-handed domain walls, due to a Dzyaloshinskii-Moriya interaction (DMI) with a DMI coefficient $D=+0.06\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}/{\mathrm{m}}^{2}$. The positive DMI coefficient is interpreted to be a consequence of B diffusion into the Ta bu…
Helical magnetic structure and the anomalous and topological Hall effects in epitaxial B20 Fe$_{1-y}$Co$_y$Ge films
2018
Epitaxial films of the B20-structure compound Fe1−yCoyGe were grown by molecular beam epitaxy on Si (111) substrates. The magnetization varied smoothly from the bulklike values of one Bohr magneton per Fe atom for FeGe to zero for nonmagnetic CoGe. The chiral lattice structure leads to a Dzyaloshinskii-Moriya interaction (DMI), and the films' helical magnetic ground state was confirmed using polarized neutron reflectometry measurements. The pitch of the spin helix, measured by this method, varies with Co content y and diverges at y∼0.45. This indicates a zero crossing of the DMI, which we reproduced in calculations using first-principles methods. We also measured the longitudinal and Hall r…