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1. Inertial spin alignment in a circular magnetic nanotube

   Bergmann, G (January 2015, Physics letters. A)

   In cobalt nanotubes with a curling magnetization, the orbital motion of the conduction electrons interacts with their spin. As the spin goes around the nanotube it cannot follow the magnetization, since with the Fermi velocity it moves too fast. Instead, we predict that the spin precesses about an axis that is almost parallel to the axis of the nanotube and that rotates with the angular velocity of the electron. Therefore, the (absolute) value of the magnetic energy of the spin |μ⋅B| is strongly reduced. The physics of the ferromagnet is considerably modified. 

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2. Photon Energy-Dependent Optical Spin-Orbit Torque in Heavy Metal-Ferromagnet Bilayers

   https://doi.org/10.1002/adfm.202307753  

   Wang, Chuangtang; Xu, Yihao; Liu, Yongmin (October 2023, Advanced Functional Materials)

   Abstract The manipulation of magnetization through optically generated ultrafast spin currents is a fascinating area that needs a thorough understanding for its potential future applications. In this work, a comprehensive investigation of helicity‐driven optical spin‐orbit torque in heavy metal/ferromagnetic metal heterostructures is presented, specifically cobalt capped with gold or platinum, subject to laser pumping at different wavelengths. The results demonstrate up to tenfold enhancement in optical spin‐orbit torque quantum efficiency for gold compared to platinum of the same thickness when pumped with a visible laser. Additionally, the study provides the first experimental analysis of the photon energy dependence of optical spin‐orbit torque and derives the optical spin orientation spectra for both gold/cobalt and platinum/cobalt heterostructures. A key insight gained from the study is the impact of photon energy‐dependent spin transport in the system, which suggests the use of a high photon energy pump for efficient spin transport. These findings highlight the potential of spin current generation and manipulation in gold/ferromagnet heterostructures for a wide range of applications such as all‐optical magnetization switching, spin‐wave generation and control, and spintronic terahertz emission. 

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3. Manipulation of the Ferromagnetism in LaCoO ₃ Thin Films Through Cation‐Stoichiometric Engineering

   https://doi.org/10.1002/aelm.202201245  

   Huang, Tongtong; Lyu, Yingjie; Huyan, Huaixun; Ni, Jinyang; Saremi, Sahar; Wang, Yujia; Yan, Xingxu; Yi, Di; He, Qing; Martin, Lane W.; et al (March 2023, Advanced Electronic Materials)

   Abstract Spin‐state transitions are an important research topic in complex oxides with the diverse magnetic states involved. In particular, the low‐spin to high‐spin transition in LaCoO₃thin films has drawn a wide range of attention due to the emergent ferromagnetic state. Although various mechanisms (e.g., structural distortion, oxygen‐vacancy formation, spin‐state ordering) have been proposed, an understanding of what really underlies the emergent ferromagnetism remains elusive. Here, the ferromagnetism in LaCoO₃thin films is systematically modulated by varying the oxygen pressure during thin‐film growth. Although the samples show dramatic different magnetization, their cobalt valence state and perovskite crystalline structure remain almost unchanged, ruling out the scenarios of both oxygen‐vacancy and spin‐ordering. This work provides compelling evidence that the tetragonal distortion due to the tensile strain significantly modifies the orbital occupancy, leading to a low‐spin to high‐spin transition with emergent ferromagnetism, while samples grown at reduced pressure demonstrate a pronounced lattice expansion due to cation‐off‐stoichiometry, which suppresses the tetragonal distortion and the consequent magnetization. This result not only provides important insight for the understanding of exotic ferromagnetism in LaCoO₃thin films, but also identifies a promising strategy to design electronic states in complex oxides through cation‐stoichiometry engineering. 

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4. Spherically symmetric Earth models yield no net electron spin

   https://doi.org/10.1103/PhysRevD.111.015015  

   Clayburn, N B; Glassford, A; Leiker, A; Uelmen, T; Lin, J F; Hunter, L R (January 2025, Physical Review D)

   Terrestrial experiments that use electrons in Earth as a spin-polarized source have been demonstrated to provide strong bounds on exotic long-range spin-spin and spin-velocity interactions. These bounds constrain the coupling strength of many proposed ultralight bosonic dark-matter candidates. Recently, it was pointed out that a monopole-dipole coupling between the Sun and the spin-polarized electrons of Earth would result in a modification of the precession of the perihelion of Earth. Using an estimate for the net spin polarization of Earth and experimental bounds on Earth’s perihelion precession, interesting constraints were placed on the magnitude of this monopole-dipole coupling. Here we investigate the spin associated with Earth’s electrons. We find that there are about $6\times {10}^{41}$spin-polarized electrons in the mantle and crust of Earth oriented antiparallel to their local magnetic field. However, when integrated over any spherically symmetric Earth model, we find that the vector sum of these spins is zero. In order to establish a lower bound on the magnitude of the net spin along Earth’s rotation axis we have investigated three of the largest breakdowns of Earth’s spherical symmetry: the large low shear-velocity provinces of the mantle, the crustal composition, and the oblate spheroid of Earth. From these investigations we conclude that there are at least $5\times {10}^{38}$spin-polarized electrons aligned antiparallel to Earth’s rotation axis. This analysis suggests that the bounds on the monopole-dipole coupling that were extracted from Earth’s perihelion precession need to be relaxed by a factor of about 2000. Published by the American Physical Society2025 

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5. Asymmetric reactions induced by electron spin polarization

   https://doi.org/10.1039/d0cp03129a  

   Bloom, B. P.; Lu, Y.; Metzger, Tzuriel; Yochelis, Shira; Paltiel, Yossi; Fontanesi, Claudio; Mishra, Suryakant; Tassinari, Francesco; Naaman, Ron; Waldeck, D. H. (January 2020, Physical Chemistry Chemical Physics)

   Essential aspects of the chiral induced spin selectivity (CISS) effect and their implications for spin-controlled chemistry and asymmetric electrochemical reactions are described. The generation of oxygen through electrolysis is discussed as an example in which chirality-based spin-filtering and spin selection rules can be used to improve the reaction's efficiency and selectivity. Next the discussion shifts to illustrate how the spin selectivity of chiral molecules (CISS properties) allows one to use the electron spin as a chiral bias for inducing asymmetric reactions and promoting enantiospecific processes. Two enantioselective electrochemical reactions that have used polarized electron spins as a chiral reagent are described; enantioselective electroreduction to resolve an enantiomer from a racemic mixture and an oxidative electropolymerization to generate a chiral polymer from achiral monomers. A complementary approach that has used spin-polarized, but otherwise achiral, molecular films to enantiospecifically associate with one enantiomer from a racemic mixture is also discussed. Each of these reaction types use magnetized films to generate the spin polarized electrons and the enantiospecificity can be selected by choice of the magnetization direction, North pole versus South pole. Possible paths for future research in this area and its compatibility with existing methods based on chiral electrodes are discussed. 

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