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  1. Abstract Transition metal oxides are promising candidates for the next generation of spintronic devices due to their fascinating properties that can be effectively engineered by strain, defects, and microstructure. An excellent example can be found in ferroelastic LaCoO 3 with paramagnetism in bulk. In contrast, unexpected ferromagnetism is observed in tensile-strained LaCoO 3 films, however, its origin remains controversial. Here we simultaneously reveal the formation of ordered oxygen vacancies and previously unreported long-range suppression of CoO 6 octahedral rotations throughout LaCoO 3 films. Supported by density functional theory calculations, we find that the strong modification of Co 3 d -O 2 p hybridization associated with the increase of both Co-O-Co bond angle and Co-O bond length weakens the crystal-field splitting and facilitates an ordered high-spin state of Co ions, inducing an emergent ferromagnetic-insulating state. Our work provides unique insights into underlying mechanisms driving the ferromagnetic-insulating state in tensile-strained ferroelastic LaCoO 3 films while suggesting potential applications toward low-power spintronic devices. 
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    Free, publicly-accessible full text available December 1, 2024
  2. The prototypical chalcogenide perovskite, BaZrS3 (BZS), with its direct bandgap of 1.7–1.8 eV, high chemical stability, and strong light–matter interactions, has garnered significant interest over the past few years. So far, attempts to grow BaZrS3 films have been limited mainly to physical vapor deposition techniques. Here, we report the fabrication of BZS thin films via a facile aqueous solution route of polymer-assisted deposition (PAD), where the polymer-chelated cation precursor films were sulfurized in a mixed CS2 and Ar atmosphere. The formation of a single-phase polycrystalline BZS thin film at a processing temperature of 900 °C was confirmed by X-ray diffraction and Raman spectroscopy. The stoichiometry of the films was verified by Rutherford Backscattering spectrometry and energy-dispersive X-ray spectroscopy. The BZS films showed a photoluminescence peak at around 1.8 eV and exhibited a photogenerated current under light illumination at a wavelength of 530 nm. Temperature-dependent resistivity analysis revealed that the conduction of BaZrS3 films under the dark condition could be described by the Efros–Shklovskii variable range hopping model in the temperature range of 60–300 K, with an activation energy of about 44 meV. 
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    Free, publicly-accessible full text available April 1, 2024
  3. Free, publicly-accessible full text available May 1, 2024
  4. Abstract

    Phase separation in manganites leads to unique magnetic and electronic properties. 50% Ca‐doped LaMnO3(LCMO), at the boundary of ferromagnetic (FM) and antiferromagnetic (AFM) states in La1‐xCaxMnO3(0 ≤ x ≤ 1), is an ideal system to study phase separation behavior. The investigation reveals the effect of a 5d‐metal perovskite SrIrO3(SIO) on the phase separation, magnetic, and magnetoresistance (MR) properties of LCMO. Single‐layer and bilayer LCMO films, both appear purely ferromagnetic along the in‐plane (IP) magnetic field direction, but show the tendency of temperature‐dependent ferromagnetic and antiferromagnetic or charge‐ordered (CO) phase separation with the out‐of‐plane (OOP) applied field. The MR, and colossal magnetoresistance (CMR), observed in LCMO/SIO bilayers are two orders and an order of magnitude (in %) larger, respectively than that in the single‐layer film. The coexistence of FM and AFM/CO phases is responsible for the CMR and MR enhancement in the LCMO/SIO bilayer, pointing toward the importance of the phase separation and competition of both the individual materials in enhancing their magnetic and electronic properties.

     
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  5. null (Ed.)
  6. Interface‐type (IT) metal/oxide Schottky memristive devices have attracted considerable attention over filament‐type (FT) devices for neuromorphic computing because of their uniform, filament‐free, and analog resistive switching (RS) characteristics. The most recent IT devices are based on oxygen ions and vacancies movement to alter interfacial Schottky barrier parameters and thereby control RS properties. However, the reliability and stability of these devices have been significantly affected by the undesired diffusion of ionic species. Herein, a reliable interface‐dominated memristive device is demonstrated using a simple Au/Nb‐doped SrTiO3(Nb:STO) Schottky structure. The Au/Nb:STO Schottky barrier modulation by charge trapping and detrapping is responsible for the analog resistive switching characteristics. Because of its interface‐controlled RS, the proposed device shows low device‐to‐device, cell‐to‐cell, and cycle‐to‐cycle variability while maintaining high repeatability and stability during endurance and retention tests. Furthermore, the Au/Nb:STO IT memristive device exhibits versatile synaptic functions with an excellent uniformity, programmability, and reliability. A simulated artificial neural network with Au/Nb:STO synapses achieves a high recognition accuracy of 94.72% for large digit recognition from MNIST database. These results suggest that IT resistive switching can be potentially used for artificial synapses to build next‐generation neuromorphic computing.

     
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  7. Abstract

    The discovery of topological Hall effect (THE) has important implications for next‐generation high‐density nonvolatile memories, energy‐efficient nanoelectronics, and spintronic devices. Both real‐space topological spin configurations and two anomalous Hall effects (AHE) with opposite polarity due to two magnetic phases have been proposed for THE‐like feature in SrRuO3(SRO) films. In this work, SRO thin films with and without THE‐like features are systematically Investigated to decipher the origin of the THE feature. Magnetic measurement reveals the coexistence of two magnetic phases of different coercivity (Hc) in both the films, but the hump feature cannot be explained by the two channel AHE model based on these two magnetic phases. In fact, the AHE is mainly governed by the magnetic phase with higherHc. A diffusive Berry phase transition model is proposed to explain the THE feature. The coexistence of two Berry phases with opposite signs over a narrow temperature range in the high Hc magnetic phase can explain the THE like feature. Such a coexistence of two Berry phases is due to the strong local structural tilt and microstructure variation in the thinner films. This work provides an insight between structure/micro structure and THE like features in SRO epitaxial thin films.

     
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