Correlation-driven eightfold magnetic anisotropy in a two-dimensional oxide monolayer.

Engineering magnetic anisotropy in two-dimensional systems has enormous scientific and technological implications. The uniaxial anisotropy universally exhibited by two-dimensional magnets has only two stable spin directions, demanding 180° spin switching between states. We demonstrate a previously unobserved eightfold anisotropy in magnetic SrRuO3 monolayers by inducing a spin reorientation in (SrRuO3)1/(SrTiO3) N superlattices, in which the magnetic easy axis of Ru spins is transformed from uniaxial 〈001〉 direction (N < 3) to eightfold 〈111〉 directions (N ≥ 3). This eightfold anisotropy enables 71° and 109° spin switching in SrRuO3 monolayers, analogous to 71° and 109° polarization switching in ferroelectric BiFeO3. First-principle calculations reveal that increasing the SrTiO3 layer thickness induces an emergent correlation-driven orbital ordering, tuning spin-orbit interactions and reorienting the SrRuO3 monolayer easy axis. Our work demonstrates that correlation effects can be exploited to substantially change spin-orbit interactions, stabilizing unprecedented properties in two-dimensional magnets and opening rich opportunities for low-power, multistate device applications

Activating the Basal Planes and Oxidized Oxygens in Layer‐Structured Na0.6CoO2 for Boosted OER Activity

Abstract With the CoO2 slabs consisting of Co4O4 cubane structure, layered NaxCoO2 are considered promising candidates for oxygen evolution reaction (OER) in alkaline media given their earth‐abundant and structural advantages. However, due to the strong adsorption of intermediates on the large basal planes, NaxCoO2 cannot meet the activity demands. Here, a novel one‐pot synthesis strategy is proposed to realize the high solubility of iron in NaxCoO2 in an air atmosphere. The optimist Na0.6Co0.9Fe0.1O2 exhibits enhanced OER activity compared to their pristine and other reported Fe‐doped NaxCoO2 counterparts. Such an enhancement is mainly ascribed to the abundant active sites on the activated basal planes and the participation of oxidized oxygen as active sites independently, which breaks the scaling relationship limit in the OER process. This work is expected to contribute to the understanding of the modification mechanism of Fe‐doped cobalt‐based oxides and the exploitation of layer‐structured oxides for energy application

Interface engineering of phase separation in SrRuO3/SrTiO3 hybrid superlattices

Most observed phase separation phenomena in complex oxides occur in systems with chemical dopants or structural defects, and theories have established the strong connection between phase separation and the random distribution of chemical dopants. Recent experiments on fabricated high-quality oxide superlattices also confirmed that the phase separation is suppressed in the clean systems without chemical disorders. Thus far, phase separation in strongly correlated oxides without the need of chemical dopants or structural defects has not been fully demonstrated. Here, we have built chemically ordered hybrid superlattices using prototypical SrRuO3 and SrTiO3 perovskite oxides. Contrary to previous understandings, we observe phase separation of two magnetic phases with different spin easy axes. We elucidate this phenomenon through first-principles calculations that the hybrid superlattices have a spontaneous structural instability, leading to a coexistence of ferromagnetic and antiferromagnetic phases. Our findings provide an alternative pathway other than chemical doping to introduce phase separation in correlated oxides and imply that phase separation can exist in clean systems without the need of chemical disorders

4D printing of shape memory inferior vena cava filters based on copolymer of poly(glycerol sebacate) acrylate-co-hydroxyethyl methacrylate (PGSA-HEMA)

Biodegradable shape memory polymers (SMP) with suitable transition temperatures (Tr) and mechanical properties are highly demanded in biomedical field as deployable medical devices. Herein, we report a 4D printing shape memory Inferior Vena Cava Filters (IVCFs), an implantation device, which could prevent the fatal pulmonary embolism, to exemplify the applicability of the biodegradable shape memory polymer in biomedical device field. The IVCF composed of poly(glycerol sebacate) acrylate-co-hydroxyethyl methacrylate (PGSA-co-HEMA) was digital light processing (DLP) 3D printed. The appropriate mechanical property and Tr = 37.8 °C, which is close to human body temperature, was tailored by tuning the ratio of the raw material. PGSA-PHEMA presents an excellent cytocompatibility, hemocompatibility and histocompatibility as implants. Besides, in vitro degradation results indicate the biodegradability but withhold the mechanical properties within the service time. Furthermore, the simulated filter deploying and fully emboli interception verifies the successful realization of the concept of rapid, minimally invasive and controllable implantation of the 4D printing of IVCFs through the SMP transformation process, and the feasibility of the filter as well. Therefore, this work provides a new biocompatible SMP and offers a new strategy for developing deployable medical devices

Enhancement of spintronic terahertz emission enabled by increasing Hall angle and interfacial skew scattering

Abstract Spintronic terahertz (THz) emitters (STEs) based on magnetic heterostructures have emerged as promising THz sources. However, it is still a challenge to achieve a higher intensity STE to satisfy all kinds of practical applications. Herein, we report a STE based on Pt0.93(MgO)0.07/CoFeB nanofilm by introducing dispersed MgO impurities into Pt, which reaches a 200% intensity compared to Pt/CoFeB and approaches the signal of 500 μm ZnTe crystal under the same pump power. We obtain a smaller spin diffusion length of Pt0.93(MgO)0.07 and an increased thickness-dependent spin Hall angle relative to the undoped Pt. We also find that the thickness of a Pt layer leads to a drastic change in the interface role in the spintronic THz emission, suggesting that the underlying mechanism of THz emission enhancement is a combined effect of enhanced bulk spin hall angle and the interfacial skew scattering by MgO impurities. Our findings demonstrate a simple way to realize high-efficiency, stable, advanced spintronic THz devices