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The ability to achieve perpendicular magnetization switching via spin–orbit torques (SOTs) is a critical advance for the development of the next generation of spintronic applications. However, the use of an external magnetic field to break the mirror symmetry is typically required to facilitate current-induced magnetization switching, which poses a significant challenge for practical implementation. Here, we demonstrate the field-free magnetization switching in the Y3Fe5O12 (YIG)/Pt heterostructure. This is achieved by introducing a lateral structure asymmetry in our devices, which can lead to an out-of-plane effective field. Our results provide an alternative solution for achieving field-free magnetization switching in nanoscale ferrimagnet-based heterostructures, thereby advancing the development of emerging SOT-based devices. [ABSTRACT FROM AUTHOR]

Machine vision techniques are widely applied for object identification in daily life and industrial production, where images are captured and processed by sensors, memories, and processing units sequentially. Neuromorphic optoelectronic synapses, as a preferable option to promote the efficiency of image recognition, are hotly pursued in non‐ionizing radiation range, but rarely in ionizing radiation including X‐rays. Here, the study proposes an X‐ray optoelectronic synapse using amorphous Ga2O3 (a‐Ga2O3) thin film. Boosted by the interfacial VO2+ defects and its slow neutralization rate, the enhanced electron tunneling process at metal/a‐Ga2O3 interface produces remarkable X‐ray‐induced post‐synaptic current, contributing to a sensitivity of 20.5, 64.3, 164.1 µC mGy−1 cm−2 for the 1st, 5th, and 10th excitation periods, respectively. Further, a 64 × 64 imaging sensor is constructed on a commercial amorphous Si (a‐Si) thin film transistor (TFT) array. The image contrast can be apparently improved under a series of X‐ray pulses due to an outstanding long‐term plasticity of the single pixel, which is beneficial to the subsequent image recognition and classification based on artificial neural network. The merits of large‐scale production ability and good compatibility with modern microelectronic techniques belonging to amorphous oxide semiconductors may promote the development of neuro‐inspired X‐ray imagers and corresponding machine vision systems. [ABSTRACT FROM AUTHOR]

Field‐free switching of a perpendicularly magnetized heavy metal/ferromagnetic metal bilayer or single alloy layer through spin‐orbit torque (SOT) provides a potential way for next‐generation spintronic devices with fast speed and high efficiency. Here, a sizable symmetry dependence of field‐free magnetization switching via an out‐of‐plane torque in CoxPt100−x single layers is reported. It is found that the sign of in‐plane SOT in CoxPt100−x when x ≤ 25 is positive. However, it changes to negative when x > 25, while the out‐of‐plane SOT changes its sign when x > 30. The polarized neutron reflectometry measurement further suggests an interface layer with rich Pt content near the substrate, which could have a strong interface effect on the out‐of‐plane SOT. The sign of the out‐of‐plane SOT, and then the polarity of the field‐free magnetization switching, is determined by the competition between the out‐of‐plane torques arising from the bulk and interface parts in the CoxPt100−x single layers. It is expected that such interface effect of the out‐of‐plane torque is desirable to the applications in spin logic devices using symmetry dependence of field‐free magnetization switching in the ferromagnetic CoPt single layers. [ABSTRACT FROM AUTHOR]

Due to the strong interlayer coupling between multiple degrees of freedom, oxide heterostructures usually produce distinct interfacial phases with unexpected functionalities. Here, we report on the realization of quasi-two-dimensional ferromagnetic state in ultrathin La0.7Sr0.3MnO3 (LSMO) layer down to two unit cells (u.c.), being sandwiched by the planar infinite-layer structured SrCuO2 layers (P-SCO). We find the LSMO/P-SCO interface coupling has greatly suppressed the magnetic dead layer of LSMO, resulting in an emergent interfacial ferromagnetic phase. Thus, robust ferromagnetic order can be maintained in the 2 u.c.-thick LSMO layer (∼7.7 Å), showing a Curie temperature of ∼260 K and remarkable perpendicular magnetic anisotropy. X-ray absorption spectra reveal notable charge transfer from Mn to Cu at the interface, and thus, resulted preferential d3z2−r2 orbital occupation for interfacial Mn ions plays an important role in the inducing of perpendicular magnetic anisotropy in quasi-two-dimensional LSMO layer. Our work demonstrates a unique approach for tuning the properties of oxides via an interface engineering of oxygen coordination in perovskite/infinite-layer heterostructures. [ABSTRACT FROM AUTHOR]

The interlayer coupling and magnetization reversal behaviors in NiFe/NiO/NiFe trilayers were investigated using polarized neutron reflectivity and Monte Carlo (MC) simulations. Our results reveal that the shape of NiFe loops transitions from square to tilted as the NiO thicknesses decrease, indicating changes in the direction of NiFe layer's easy axis. This phenomenon can be attributed to variations occurring at NiO/NiFe interfaces for different NiO layer thicknesses. With thin NiO layer, interdiffusion at the NiO/NiFe interfaces leads to frustrated coupling, resulting in a noncollinear interlayer coupling. This observation is supported by MC simulations. Conversely, hardly any coupling frustration is observed for the sample with a thick NiO layer. Our findings propose a novel way to tailor the interlayer coupling through interface engineering. [ABSTRACT FROM AUTHOR]

Numerous studies pay more attention to the heterophase interfaces of nanocomposites due to their effective sinks for radiation-induced point defects and traps for helium. An amorphous structure with excessive free volume also possesses high He solubility and irradiation resistance, but its effect on helium irradiation of the nanocomposites is not clear. Here, the helium irradiation effect of a crystalline/amorphous/crystalline sandwich structured W/Amorphous/Cu nanocomposite (W/A/Cu) is investigated. The results show that helium swelling resistance of a W/A/Cu nanocomposite is enhanced after introducing an amorphous layer due to strong sink strength of the crystalline/amorphous-W(Cu)/A interface and high He solubility of amorphous layers. This result sheds light on the design of radiation-tolerant materials for advanced nuclear reactor applications. [ABSTRACT FROM AUTHOR]

Ferromagnetic materials with a strong spin‐orbit coupling (SOC) have attracted much attention in recent years because of their exotic properties and potential applications in energy‐efficient spintronics. However, such materials are scarce in nature. Here, a proximity‐induced paramagnetic to ferromagnetic transition for the heavy transition metal oxide CaRuO3 in (001)‐(LaMnO3/CaRuO3) superlattices is reported. Anomalous Hall effect is observed in the temperature range up to 180 K. Maximal anomalous Hall conductivity and anomalous Hall angle are as large as ∼15 Ω−1 cm−1 and ∼0.93%, respectively, by one to two orders of magnitude larger than those of the typical 3d ferromagnetic oxides such as La0.67Sr0.33MnO3. Density functional theory calculations indicate the existence of avoid band crossings in the electronic band structure of the ferromagnetic CRO layer, which enhances Berry curvature thus strong anomalous Hall effects. Further evidences from polarized neutron reflectometry show that the CaRuO3 layers are in a fully ferromagnetic state (∼0.8 μB/Ru), in sharp contrast to the proximity‐induced canted antiferromagnetic state in 5d oxides SrIrO3 and CaIrO3 (∼0.1 μB/Ir). More than that, the magnetic anisotropy of the (001)‐(LaMnO3/CaRuO3) superlattices is eightfold symmetric, showing potential applications in the technology of multistate data storage. [ABSTRACT FROM AUTHOR]

By modifying the entangled multi‐degrees of freedom of transition‐metal oxides, interlayer coupling usually produces interfacial phases with unusual functionalities. Herein, a symmetry‐mismatch‐driven interfacial phase transition from paramagnetic to ferromagnetic state is reported. By constructing superlattices using CaRuO3 and SrTiO3, two oxides with different oxygen octahedron networks, the tilting/rotation of oxygen octahedra near interface is tuned dramatically, causing an angle increase from ≈150° to ≈165° for the RuORu bond. This in turn drives the interfacial layer of CaRuO3, ≈3 unit cells in thickness, from paramagnetic into ferromagnetic state. The ferromagnetic order is robust, showing the highest Curie temperature of ≈120 K and the largest saturation magnetization of ≈0.7 µB per formula unit. Density functional theory calculations show that the reduced tilting/rotation of RuO6 octahedra favors an itinerant ferromagnetic ground state. This work demonstrates an effective phase tuning by coupled octahedral rotations, offering a new approach to explore emergent materials with desired functionalities. [ABSTRACT FROM AUTHOR]

Complex oxides with tunable structures have many fascinating properties, though high-quality complex oxide epitaxy with precisely controlled composition is still out of reach. Here we have successfully developed solution-based single-crystalline epitaxy for multiferroic (1- x)BiTi(1- y)/2Fe y Mg(1- y)/2O3–(x)CaTiO3 (BTFM–CTO) solid solution in large area, confirming its ferroelectricity at the atomic scale with strong spontaneous polarization. Careful compositional tuning leads to a bulk magnetization of 0.07 ± 0.035 μB/Fe at room temperature, enabling magnetically induced polarization switching exhibiting a large magnetoelectric coefficient of 2.7–3.0 × 10−7 s/m. This work demonstrates the great potential of solution processing in large-scale complex oxide epitaxy and establishes novel room-temperature magnetoelectric coupling in epitaxial BTFM–CTO film, making it possible to explore a much wider space of composition, phase, and structure that can be easily scaled up for industrial applications. [ABSTRACT FROM AUTHOR]

Ferromagnetic materials with a strong spin‐orbit coupling (SOC) have attracted much attention in recent years because of their exotic properties and potential applications in energy‐efficient spintronics. However, such materials are scarce in nature. Here, a proximity‐induced paramagnetic to ferromagnetic transition for the heavy transition metal oxide CaRuO3 in (001)‐(LaMnO3/CaRuO3) superlattices is reported. Anomalous Hall effect is observed in the temperature range up to 180 K. Maximal anomalous Hall conductivity and anomalous Hall angle are as large as ∼15 Ω−1 cm−1 and ∼0.93%, respectively, by one to two orders of magnitude larger than those of the typical 3d ferromagnetic oxides such as La0.67Sr0.33MnO3. Density functional theory calculations indicate the existence of avoid band crossings in the electronic band structure of the ferromagnetic CRO layer, which enhances Berry curvature thus strong anomalous Hall effects. Further evidences from polarized neutron reflectometry show that the CaRuO3 layers are in a fully ferromagnetic state (∼0.8 μB/Ru), in sharp contrast to the proximity‐induced canted antiferromagnetic state in 5d oxides SrIrO3 and CaIrO3 (∼0.1 μB/Ir). More than that, the magnetic anisotropy of the (001)‐(LaMnO3/CaRuO3) superlattices is eightfold symmetric, showing potential applications in the technology of multistate data storage. [ABSTRACT FROM AUTHOR]