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Register a new userLongitudinal Spin Seebeck effect in Pyrochlore Iridates with Bulk and Interfacial Dzyaloshinskii-Moriya interaction
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The longitudinal spin-Seebeck effect (SSE) in magnetic insulator$|$non-magnetic metal heterostructures has been theoretically studied primarily with the assumption of an isotropic interfacial exchange coupling. Here, we present a general theory of the SSE in the case of an antisymmetric Dzyaloshinskii-Moriya interaction (DMI) at the interface, in addition to the usual Heisenberg form. We numerically evaluate the dependence of the spin current on the temperature and bulk DMI using a pyrochlore iridate as a model insulator with all-in all-out (AIAO) ground state configuration. We also compare the results of different crystalline surfaces arising from different crystalline orientations and conclude that the relative angles between the interfacial moments and Dzyaloshinskii-Moriya vectors play a significant role in the spin transfer. Our work extends the theory of the SSE by including the anisotropic nature of the interfacial Dzyaloshinskii-Moriya exchange interaction in magnetic insulator$|$non-magnetic metal heterostructures and can suggest possible materials to optimize the interfacial spin transfer in spintronic devices.
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We report current-induced domain wall motion (CIDWM) in TaCo20Fe60B20MgO 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 direction and 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 mJ/m2. The positive DMI coefficient is interpreted to be a consequence of boron diffusion into the tantalum buffer layer during annealing. In a PtCo68Fe22B10MgO nanowire CIDWM along the electron flow was observed, corroborating this interpretation. The experimental results are compared to 1D-model simulations including the effects of pinning. This advanced modelling allows us to reproduce the experiment outcomes and reliably extract a spin-Hall angle {theta}SH=-0.11 for Ta in the nanowires, showing the importance of an analysis that goes beyond the currently used model for perfect nanowires.
The Dzyaloshinskii-Moriya interaction (DMI), being one of the origins for chiral magnetism, is currently attracting huge attention in the research community focusing on applied magnetism and spintronics. For future applications an accurate measurement of its strength is indispensable. In this work, we present a review of the state of the art of measuring the coefficient $D$ of the Dzyaloshinskii-Moriya interaction, the DMI constant, focusing on systems where the interaction arises from the interface between two materials. The measurement techniques are divided into three categories: a) domain wall based measurements, b) spin wave based measurements and c) spin orbit torque based measurements. We give an overview of the experimental techniques as well as their theoretical background and models for the quantification of the DMI constant $D$. We analyze the advantages and disadvantages of each method and compare $D$ values in different stacks. The review aims to obtain a better understanding of the applicability of the different techniques to different stacks and of the origin of apparent disagreement of literature values.
We study in this paper magnetic properties of a system of quantum Heisenberg spins interacting with each other via a ferromagnetic exchange interaction J and an in-plane Dzyaloshinskii-Moriya interaction D. The non-collinear ground state due to the competition between J and D is determined. We employ a self-consistent Greenfunction theory to calculate the spin-wave spectrum and the layer magnetizations at finite T in two and three dimensions as well as in a thin film with surface effects. Analytical details and the validity of the method are shown and discussed.
The interfacial Dzyaloshinskii-Moriya interaction (DMI) has been shown to stabilize homochiral Neel-type domain walls in thin films with perpendicular magnetic anisotropy and as a result permit them to be propagated by a spin Hall torque. In this study, we demonstrate that in Ta/Co$_{20}$Fe$_{60}$B$_{20}$/MgO the DMI may be influenced by annealing. We find that the DMI peaks at $D=0.057pm0.003$ mJ/m$^{2}$ at an annealing temperature of 230 $^{circ}$C. DMI fields were measured using a purely field-driven creep regime domain expansion technique. The DMI field and the anisotropy field follow a similar trend as a function of annealing temperature. We infer that the behavior of the DMI and the anisotropy are related to interfacial crystal ordering and B expulsion out of the CoFeB layer as the annealing temperature is increased.
We show a method to control magnetic interfacial effects in multilayers with Dzyaloshinskii-Moriya interaction (DMI) using helium (He$^{+}$) ion irradiation. We compare results from SQUID magnetometry, ferromagnetic resonance as well as Brillouin light scattering results on multilayers with DMI as a function of irradiation fluence to study the effect of irradiation on the magnetic properties of the multilayers. Our results show clear evidence of the He$^{+}$ irradiation effects on the magnetic properties which is consistent with interface modification due to the effects of the He$^{+}$ irradiation. This external degree of freedom offers promising perspectives to further improve the control of magnetic skyrmions in multilayers, that could push them towards integration in future technologies, such as in low-power neuromorphic computing.
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