Current-induced magnetization switching of exchange-biased NiO heterostructures characterized by spin-orbit torque
Krzysztof Grochot, Łukasz Karwacki, Stanisław Łazarski, Witold Skowroński, Jarosław Kanak, Wiesław Powroźnik, Piotr Kuświk, Mateusz Kowacz, Feliks Stobiecki, Tomasz Stobiecki
In this work, we study magnetization switching induced by spin-orbit torque in W(Pt)/Co/NiO heterostructures with variable thickness of heavy-metal layers W and Pt, perpendicularly magnetized Co layer and an antiferromagnetic NiO layer. Using current-driven switching, magnetoresistance and anomalous Hall effect measurements, perpendicular and in-plane exchange bias field were determined. Several Hall-bar devices possessing in-plane exchange bias from both systems were selected and analyzed in relation to our analytical switching model of critical current density as a function of Pt and W thickness, resulting in estimation of effective spin Hall angle and perpendicular effective magnetic anisotropy. We demonstrate in both the Pt/Co/NiO and the W/Co/NiO systems the deterministic Co magnetization switching without external magnetic field which was replaced by in-plane exchange bias field. Moreover, we show that due to a higher effective spin Hall angle in W than in Pt-systems the relative difference between the resistance states in the magnetization current switching to difference between the resistance states in magnetic field switching determined by anomalous Hall effect ($ΔR/ΔR_{\text{AHE}}$) is about twice higher in W than Pt, while critical switching current density in W is one order lower than in Pt-devices. The current switching stability and training process is discussed in detail.
Spin backflow and spin-memory loss have been well established to considerably lower the interfacial spin transmissivity of metallic magnetic interfaces and thus the energy efficiency of spin-orbit torque technologies. Here we report that spin backflow and spin-memory loss at Pt-based heavy metal/ferromagnet interfaces can be effectively eliminated by inserting an insulating paramagnetic NiO layer of optimum thickness. The latter enables the thermal magnon-mediated essentially unity spin-current transmission at room temperature due to considerably enhanced effective spin-mixing conductance of t…
We report the control of vertical magnetization shift (VMS) and exchange bias through spin-orbit torque (SOT) in Pt/Co/Ir25Mn75/Co heterostructure device. The exchange bias accompanying with a large relative VMS of about 30 % is observed after applying a single pulse 40 mA in perpendicular field of 2 kOe. Furthermore, the field-free SOT-induced variations of VMS and exchange bias is also observed, which would be related to the effective built-in out-of-plane field due to unequal upward and downward interfacial spin populations. The SOT-induced switched fraction of out-of-plane interfacial spin…
The manipulation of magnetic properties using either electrical currents or gate bias is the key of future high-impact nanospintronics applications such as spin-valve read heads, non-volatile logic, and random-access memories. The current technology for magnetic switching with spin-transfer torque requires high current densities, whereas gate-tunable magnetic materials such as ferromagnetic semiconductors and multiferroic materials are still far from practical applications. Recently, magnetic switching induced by pure spin currents using the spin Hall and Rashba effects in heavy metals, called…
Antiferromagnets are outstanding candidates for the next generation of spintronic applications, with great potential for downscaling and decreasing power consumption. Recently, the manipulation of bulk properties of antiferromagnets has been realized by several different approaches. However, the interfacial spin order of antiferromagnets is an important integral part of spintronic devices, thus the successful control of interfacial antiferromagnetic spins is urgently desired. Here, we report the high controllability of interfacial spins in antiferromagnetic / ferromagnetic / heavy metal hetero…
The emergent two-dimensional (2D) ferromagnetic materials with unique magnetic properties have endowed great potential for next-generation spintronic devices with extraordinary merits of high flexibility, easy controllability, and high heretointegrability, which is expected to promote the development of Moore's Law continuously. However, it is extremely challenging to realize magnetic switching with ultra-low power consumption at room temperature. Here, we demonstrate the room-temperature spin-orbit torque (SOT) driven magnetization switching in a well-epitaxial all-van der Waals (vdW) heteros…
Spin-orbit torque can drive electrical switching of magnetic layers. Here, we report that at least for micrometer-sized samples there is no simple correlation between the efficiency of dampinglike spin-orbit torque (ξ_DL^j) and the critical switching current density of perpendicularly magnetized spin-current generator/ferromagnet heterostructures. We find that the values of ξ_DL^j based on switching current densities can either under- or over-estimated ξ_DL^j by up to tens of times in a domain-wall depinning analysis, while in the macrospin analysis based on the switching current density ξ_DL^…
Recent studies rediscovered the crucial role of field-like spin orbit torque (SOT) in nanosecond-timescale SOT dynamics. However, there is not yet an effective way to control its relative amplitude. Here, we experimentally modulate the field-like SOT in W/CoFeB/MgO trilayers through tuning the interfacial spin accumulation. By performing spin Hall magnetoresistance measurement, we find that the CoFeB with enhanced spin dephasing, either generated from larger layer thickness or from proper annealing, can distinctly boost the spin absorption and enhance the interfacial spin mixing conductance G_…
We report unambiguously experimental evidence of a strong orbital current in Nb films with weak spin-orbit coupling via the spin-torque ferromagnetic resonance (ST-FMR) spectrum for Fe/Nb and Co/Nb bilayers. The sign change of the damping-like torque in Co/Nb demonstrates a large spin-orbit correlation and thus great efficiency of orbital torque in Co/Nb. By studying the efficiency as a function of the thickness of Nb sublayer, we reveal a long orbital diffusion length (~3.1 nm) of Nb. Further planar Hall resistance (PHE) measurements at positive and negative applying current confirm the nonlo…
Spin Hall magnetoresistance (SMR) has been observed in Pt/NiO/Y3Fe5O12 (YIG) heterostructures with characteristics very different from those in Pt/YIG. We show that the SMR in Pt/NiO/YIG strongly correlates with spin conductance, both sharing very strong temperature dependence due to antiferromagnetic magnons and spin fluctuation. This phenomenon indicates that spin current generated by spin Hall effect in the Pt transmits through the insulating NiO and is reflected from the NiO/YIG interface. Inverted SMR has been observed below a temperature which increases with the NiO thickness, suggesting…
Electric-field control of magnetization dynamics is fundamentally and technologically important for future spintronic devices. Here, based on electric-field control of both magnetic anisotropy and spin--orbit torque, two distinct methods are presented for switching the magnetization in topological insulator (TI)/magnetic-TI hybrid systems. The magnetic anisotropy energy in magnetic TIs is formulated analytically as a function of the Fermi energy, and it is confirmed that the out-of-plane magnetization is always favored for the partially occupied surface band. Also proposed is a transistor-like…
Spin-orbit torque is a promising mechanism for writing magnetic memories, while field-effect transistors are the gold-standard device for logic operation. The spin-orbit torque field effect transistor (SOTFET) is a proposed device that couples a spin-orbit-torque-controlled ferromagnet to a semiconducting transistor channel via the transduction in a magnetoelectric multiferroic. This allows the SOTFET to operate as both a memory and a logic device, but its realization depends on the choice of appropriate materials. In this report, we discuss and parametrize the types of materials that can lead…
We show that ideal memristors - devices whose resistance is proportional to the charge that flows through them - can be realized using spin torque-driven viscous magnetization dynamics. The latter can be accomplished in the spin liquid state of thin-film heterostructures with frustrated exchange, where memristive response is tunable by proximity to the glass transition, while current-induced Joule heating facilitates nonvolatile operation and second-order memristive functionality beneficial for neuromorphic applications. Ideal memristive behaviors can be achieved in other systems characterized…
Interfacial chirality-induced magnetic-field-free switching with high energy efficiency in all-vdW heterostructures
Seoul National University（首尔大学）；Pohang University of Science and Technology（浦项科技大学）；Kyungpook National University（庆北国立大学）；Washington University in St. Louis（圣路易斯华盛顿大学）；University of California（加州大学）；Oak Ridge National Laboratory（橡树岭国家实验室）
