Tuning the Dzyaloshinskii–Moriya interaction in Pt/Co/MgO heterostructures through the MgO thickness

Abstract

The interfacial Dzyaloshinskii-Moriya interaction (DMI) in ferromagnetic/heavy metal ultra-thin film structures has attracted a lot of attention thanks to its capability to stabilize Néel-type domain walls (DWs) and magnetic skyrmions for the realization of non-volatile memory and logic devices. In this study, we demonstrate that magnetic properties in perpendicularly magnetized Ta/Pt/Co/MgO/Pt heterostructures, such as magnetization and DMI, can be significantly influenced by the MgO thickness. To avoid the excessive oxidation of Co, an ultrathin Mg layer is inserted to improve the quality of the Co-MgO interface. By using field-driven domain wall expansion in the creep regime, we find that non-monotonic tendencies of the DMI field appear when changing the thickness of MgO. With the insertion of a monatomic Mg layer, the strength of the DMI could reach a high level and saturate. We conjecture that the efficient control of the DMI is a result of subtle changes of both Pt/Co and Co/MgO interfaces, which provides a method to optimize the design of ultra-thin structures achieving skyrmion electronics.

Manipulation of Magnetization by Spin–Orbit Torque

“…The domain wall velocity can reach up to 400 m s −1 in an ultrathin Pt/Co/AlO x nanowire. The asymmetric layer structure can induce large DMI . Thiaville et al .…”

Field-free spin-orbit torque switching of a perpendicular ferromagnet with Dzyaloshinskii-Moriya interaction

“…Incidentally, the spin-orbit coupling at the interface leads to chiral interactions, Dzyaloshinskii-Moriya interaction (DMI), appearing at the FM/HM interface. [23][24][25][26][27][28] The effect of DMI on SOT switching has been studied recently both experimentally [29][30][31] and through micromagnetic simulations. [32][33][34][35] DMI can induce non-uniform magnetization textures of a definite chirality and significantly affects the magnetization reversal process.…”

Magnetization Dynamics Modulated by Dzyaloshinskii-Moriya Interaction in the Double-Interface Spin-Transfer Torque Magnetic Tunnel Junction

“…DMI favors the chiral magnetic textures (e.g. spin spirals, skyrmions, and Neel type domain walls) and dramatically affects the magnetization dynamics, as validated by the recent studies [14][15][16][17][18][19][20][21][22][23][24][25]. It is important to mention that the role of the DMI will become more complicated in the double-interface MTJ, since two FM/HM interfaces need to be considered together with an additional RKKY interaction.…”

“…On the other hand, the heavy metal works as a spacer between two ferromagnetic layers of the composite free layer to provide the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction [11], which ferromagnetically couples the magnetizations of the two ferromagnetic layers in order that they behaves like an identical layer. However, recent works demonstrate that an antisymmetric exchange coupling called Dzyaloshinskii-Moriya interaction (DMI) [12][13] inevitably exists at the FM/HM interface due to the lack of inversion symmetry [14][15][16][17][18]. Therefore the DMI is naturally induced in the double-interface MTJ with FM/HM structures.…”