Local Vibrational Modes Competitions in Mn-Doped ZnO Epitaxial Films with Tunable Ferromagnetism

We reported spectroscopic investigations of high quality Mn-doped ZnO (ZnMnO) films grown by oxygen plasma-assisted molecular beam epitaxy. Raman scattering spectra revealed two local vibrational modes (LVMs) associated with Mn dopants at 523 and 712cm-1. The LVMs and magnetic properties of ZnMnO films can be synchronously modulated by post annealing processing or by introducing tiny Co. The relative intensity of two LVMs clearly shows competitions arising from uncompensated acceptor and donor defects competition for ferromagnetic and nonmagnetic films. The experimental results indicated that LVM at 523 cm-1 is attributed to Mn—(Zinc-vacancy) complexes, while LVM at 712 cm-1 is attributed to Mn—(Oxygen-vacancy) complexes

Production of high-energy 6-Ah-level Li | |LiNi0.83Co0.11Mn0.06O2 multi-layer pouch cells via negative electrode protective layer coating strategy

Abstract Stable lithium metal negative electrodes are desirable to produce high-energy batteries. However, when practical testing conditions are applied, lithium metal is unstable during battery cycling. Here, we propose poly(2-hydroxyethyl acrylate-co-sodium benzenesulfonate) (PHS) as negative electrode protective layer. The PHS contains soft poly (2-hydroxyethyl acrylate) and poly(sodium p-styrene sulfonate), which improve electrode flexibility, connection with the Cu current collector and transport of Li ions. Transmission electron cryomicroscopy measurements reveal that PHS induces the formation of a solid electrolyte interphase with a fluorinated rigid and crystalline internal structure. Furthermore, theoretical calculations suggest that the -SO3 - group of poly(sodium p-styrene sulfonate) promotes Li-ion motion towards interchain migration through cation-dipole interaction, thus, enabling uniform Li-ion diffusion. Electrochemical measurements of Li | |PHS-coated-Cu coin cells demonstrate an average Coulombic efficiency of 99.46% at 1 mA/cm2, 6 mAh/cm2 and 25 °C. Moreover, when the PHS-coated Li metal negative electrode is paired with a high-areal-capacity LiNi0.83Co0.11Mn0.06O2-based positive electrode in multi-layer pouch cell configuration, the battery delivers an initial capacity of 6.86 Ah (corresponding to a specific energy of 489.7 Wh/kg) and, a 91.1% discharge capacity retention after 150 cycles at 2.5 mA/cm2, 25 °C and 172 kPa

The anomalous Hall effect controlled by residual epitaxial strain in antiferromagnetic Weyl semimetal Mn3Sn thin films grown by molecular beam epitaxy

The large anomalous Hall effect (AHE) in antiferromagnetic(AFM) Weyl semimetal Mn3Sn attracts intensive attentions in spintronics. Here, we report the structural property of high quality Mn3Sn thin film on insulator substrate MgO(110) by molecular beam epitaxy (MBE), and AHE in control of residual mismatch strain between Mn3Sn film and substrate. We are able to grow strain-free Mn3Sn(10 1¯ 0) films or alternatively strained Mn3Sn(11 2¯ 0) films via a three-step process. The strain-free Mn3Sn film has large anomalous Hall conductivity up to 30 Ω-1cm−1 at room temperature, which is comparable to bulk Mn3Sn. In contrast, AHE is switched off in strained Mn3Sn film due to piezomagnetic effect under a uniaxial compress strain of ∼2.0%. These findings provide a deeper understanding on AFM spintronic applications

Enhancing s, p-d exchange interactions at room temperature by carrier doping in single crystalline Co0.4Zn0.6O epitaxial films

Magnetic doping of semiconductors has been actively pursued because of their potential applications in the spintronic devices. Central to these efforts is a drive to control the mutual interactions between their magnetic properties (supported by d electrons of the magnetic ions) and their semiconductor properties (supported by s and/or p electrons) at room temperature (RT). Despite the long, intensive efforts, the experimental evidence of thermally robust s, p-d coupling in a semiconductor remains scarce and controversial. Here, we report the enhancement of RT ferromagnetic s, p-d exchange interaction by means of carrier doping in single crystalline Co0.4Zn0.6O epitaxial films with a high Co concentration. Magneto-transport measurements reveal that spin-polarized conducting carriers are produced at RT and are increased with the carrier density through Ga3þ doping, owing to the s, p-d coupling between Ga (4s), O (2p), and Co (3d) orbitals. With the ability to individually control carrier density and magnetic doping, single crystalline Ga(Co, Zn)O films can lay a solid foundation for the development of practical semiconductor spintronic devices operable at R

Growth-Controlled Engineering of Magnetic Exchange Interactions in Single Crystalline GaCoZnO1-v Epitaxial Films with High Co Concentration

While semiconductor spintronics promises lower switching energy and faster speed, a major limitation on its development as a viable technology is the lack of room temperature ferromagnetic semiconductor materials. The material challenge is great, because not only magnetic and electronic doping but also thermally robust coupling between them are required for a room temperature ferromagnetic semiconductor. Here, we report the growth-controlled engineering of magnetic exchange interactions in single crystalline GaCoZnO1-v epitaxial films with high Co concentrations (0.3 ≤ x ≤ 0.45) by controlling oxygen vacancy and carrier density through Ga3+ doping. Strong ferromagnetism, spin-split impurity states, and spin-polarized electrical transport are realized and well controlled at room temperature by tailoring the s,p-d exchange coupling. This room temperature ferromagnetic semiconductor, which offers the ability to individually control carrier density and magnetic doping, will lay a solid foundation for the development of practical spintronic devices operating at room temperature

Growth-Controlled Engineering of Magnetic Exchange Interactions in Single Crystalline GaCoZnO_1‑v Epitaxial Films with High Co Concentration

While semiconductor spintronics promises lower switching energy and faster speed, a major limitation on its development as a viable technology is the lack of room temperature ferromagnetic semiconductor materials. The material challenge is great, because not only magnetic and electronic doping but also thermally robust coupling between them are required for a room temperature ferromagnetic semiconductor. Here, we report the growth-controlled engineering of magnetic exchange interactions in single crystalline GaCoZnO_1‑<i>v</i> epitaxial films with high Co concentrations (0.3 ≤ <i>x</i> ≤ 0.45) by controlling oxygen vacancy and carrier density through Ga³⁺ doping. Strong ferromagnetism, spin-split impurity states, and spin-polarized electrical transport are realized and well controlled at room temperature by tailoring the s,p–d exchange coupling. This room temperature ferromagnetic semiconductor, which offers the ability to individually control carrier density and magnetic doping, will lay a solid foundation for the development of practical spintronic devices operating at room temperature