Interface control of the magnetic chirality in CoFeB/MgO heterostructures with heavy-metal underlayers

Abstract

Recent advances in the understanding of spin orbital effects in ultrathin magnetic heterostructures have opened new paradigms to control magnetic moments electrically. The Dzyaloshinskii-Moriya interaction (DMI) is said to play a key role in forming a Néel-type domain wall that can be driven by the spin Hall torque. Here we show that the strength and sign of the DMI can be changed by modifying the adjacent heavy-metal underlayer (X) in perpendicularly magnetized X/CoFeB/MgO heterostructures. The sense of rotation of a domain wall spiral is reversed when the underlayer is changed from Hf, Ta to W and the strength of DMI varies as the filling of 5d orbitals, or the electronegativity, of the heavy-metal layer changes. The DMI can even be tuned by adding nitrogen to the underlayer, thus allowing interface engineering of the magnetic texture in ultrathin magnetic heterostructures.

Unlocking Bloch-type chirality in ultrathin magnets through uniaxial strain

“…The results introduce rich possibilities to influence DW dynamics by combining intrinsic phenomena such as spin Hall effects [18][19][20][21]36,37 , Rashba effects 18,36,38,39 or the DMI 15,18 , not only with magnetoelastically induced anisotropy (as we have shown in this work), but also with piezo-induced strain 40 ARTICLE nanowire shape-induced anisotropy 42 or external magnetic fields [19][20][21]43,44 , which may open up new opportunities to design spin-orbitronics devices.…”

“…It was recently found that chiral Néel walls in film and multilayer structures enable fast current-driven DW motion and spin texture-dependent DW propagation direction 15,[18][19][20][21] . A numerical study also predicts that introducing chirality of Bloch walls into magnetic films can extend possibilities to manipulate DW propagation behaviours to new geometries 18 .…”

Temperature dependence of spin-orbit torques across the magnetic compensation point in a ferrimagnetic TbCo alloy film

“…SOTs with both a fieldlike and dampinglike character can manifest in such systems, with the latter capable of driving magnetization switching [1][2][3][4][5]7,9,[11][12][13]15,21,22,24] and magnetic domain wall motion [26][27][28][29][30][31]. SOTs have been identified and quantified by a variety of techniques including spin-torque ferromagnetic resonance [2,7,14,17,19,25], quasistatic magnetization tilting probed through harmonic voltage measurements [6,[8][9][10][11][12][13]17,[19][20][21][22][23][24][25][26]28,31], and current-induced hysteresis loop shift measurements [18,32,33]. Most studies of SOTs have focused on ultrathin metallic ferromagnet/heavy-metal bilayers with interfacial perpendicular magnetic ani...…”

Effect of rare earth metal on the spin-orbit torque in magnetic heterostructures

“…Current-driven magnetization switching [1][2][3][4][5][6][7] and magnetic domain wall motion [8][9][10][11][12][13][14][15][16][17][18][19] have been widely investigated for device applications such as nonvolatile magnetic memory. 9,20 More recently, current-induced control of the magnetization has been achieved by current-induced spin-orbit torques (SOTs) originating from heavy metal layers with strong spin-orbit coupling, from which the resulting effective fields are strong enough to control the magnetization in adjacent ultra-thin ferromagnetic layers.…”

“…9,20 More recently, current-induced control of the magnetization has been achieved by current-induced spin-orbit torques (SOTs) originating from heavy metal layers with strong spin-orbit coupling, from which the resulting effective fields are strong enough to control the magnetization in adjacent ultra-thin ferromagnetic layers. [1][2][3][4][5][6][7]11,[13][14][15][16][17][18][19][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] In the ferromagnet/heavy metal system, SOTs can arise from the interfacial Rashba effect 11,21,24 and the bulk spin Hall effect (SHE), [2][3][4]7,13,16,22,23,27,[29][30][31][32]…”