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Novel Spintronic Responses of Novel Materials: A Tale of Two Systems
Paul Haney,Fei Xue,Duarte Pereira de Sousa,Jian-Ping Wang,Tony Low 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
The discovery of new materials with unique magnetic ordering, crystal symmetries, and topological properties continues to stimulate the development of new spintronic devices. Spin-orbit coupling underlies many of the spintronic applications in materials, as it couples the electron spin with its real space motion and often plays a key role in determining the topological properties of a material’s electronic structure. In this talk we’ll describe the unique properties of two quite distinct materials systems: antiferromagnetic bilayer CrI3 and magnetic tunnel junctions composed of one or more magnetic Weyl semimetals. Bilayer CrI3 is a two-dimensional Van der Waals material in which two ferromagnetic CrI3 monolayers are coupled antiferromagnetically. We consider electron doped CrI3 and theoretically study the current-induced torques present in this material. In the purely antiferromagnetic state, the two individually inversion symmetry-broken layers of CrI3 form inversion partners, like the well-studied CuMnAs and MnAu. However, the exchange and anisotropy energies are similar in magnitude, unlike previously studied antiferromagnets in which the exchange energy is dominant. This difference leads to qualitatively different behaviors in this material. Using a combination of first-principles calculations of the spin-orbit torque and an analysis of the ensuing spin dynamics, we show that the deterministic electrical switching of the Néel vector is the result of damping like spin-orbit torque, which is staggered on the magnetic sublattices. We then present results on magnetic tunnel junctions composed of one or more magnetic Weyl semimetal layers. For an asymmetric magnetic tunnel junction containing a conventional ferromagnet and a magnetic Weyl semimetal contact, we find unique features of the spin transfer torque. The Weyl semimetal hosts chiral bulk states and topologically protected Fermi arc surface states which we find govern the voltage behavior and efficiency of the spin transfer torque. We discuss the existence of a large field-like torque acting on the magnetic Weyl semimetal, whose efficiency can exceed the theoretical maximum of conventional magnetic tunnel junctions. This large field-like torque is derived from the Fermi arc spin texture and displays a counter-intuitive dependence on the Weyl nodes separation. We finally consider a magnetic tunnel junction composed of two Weyl semimetal contacts. For this system, we show that chirality-magnetization locking leads to a gigantic tunneling magnetoresistance ratio, an effect that does not rely on spin filtering by the tunnel barrier. Our results shed light on the new physics of multilayered spintronic devices comprising of magnetic Weyl semimetals, which might open doors for new energy efficient spintronic devices.
Modifying Risk Factors in the Management of Erectile Dysfunction: A Review
Kenneth J DeLay,Nora Haney,Wayne JG Hellstrom 대한남성과학회 2016 The World Journal of Men's Health Vol.34 No.2
Erectile dysfunction (ED) is prevalent among men and its presence is often an indicator of systemic disease. Risk factors for ED include cardiovascular disease, hypertension, diabetes mellitus (DM), tobacco use, hyperlipidemia, hypogonadism, lower urinary tract symptoms, metabolic syndrome, and depression. Addressing the modifiable risk factors frequently improves a patient’s overall health and increases lifespan. The literature suggests that smoking cessation, treatment of hyperlipidemia, and increasing physical activity will improve erectile function in many patients. How the treatment of DM, depression, and hypogonadism impacts erectile function is less clear. Clinicians need to be aware that certain antihypertensive agents can adversely impact erectile function. The treatment of men with ED needs to address the underlying risk factors to ameliorate the disease process.
k-asymmetric spin splitting at the interface between transition metal ferromagnets and heavy metals
Grytsyuk, Sergiy,Belabbes, Abderrezak,Haney, Paul M.,Lee, Hyun-Woo,Lee, Kyung-Jin,Stiles, M. D.,Schwingenschlö,gl, Udo,Manchon, Aurelien American Physical Society 2016 Physical Review B Vol.93 No.17
<P>We systematically investigate the spin-orbit coupling-induced band splitting originating from inversion symmetry breaking at the interface between a Co monolayer and 4d (Tc, Ru, Rh, Pd, and Ag) or 5d (Re, Os, Ir, Pt, and Au) transition metals. In spite of the complex band structure of these systems, the odd-in-k spin splitting of the bands displays striking similarities with the much simpler Rashba spin-orbit coupling picture. We establish a clear connection between the overall strength of the odd-in-k spin splitting of the bands and the charge transfer between the d orbitals at the interface. Furthermore, we show that the spin splitting of the Fermi surface scales with the induced orbital moment, weighted by the spin-orbit coupling.</P>
Kim Doyun,Bak Myeong Seong,Park Haney,Baek In Seon,Chung Geehoon,박재현,Ahn Sora,Park Seon-Young,배현수,Park Hi-Joon,김선광 한국뇌신경과학회 2023 Experimental Neurobiology Vol.32 No.3
Quantification of tyrosine hydroxylase (TH)-positive neurons is essential for the preclinical study of Parkinson’s disease (PD). However, manual analysis of immunohistochemical (IHC) images is labor-intensive and has less reproducibility due to the lack of objectivity. Therefore, several automated methods of IHC image analysis have been proposed, although they have limitations of low accuracy and difficulties in practical use. Here, we developed a convolutional neural network-based machine learning algorithm for TH+ cell counting. The developed analytical tool showed higher accuracy than the conventional methods and could be used under diverse experimental conditions of image staining intensity, brightness, and contrast. Our automated cell detection algorithm is available for free and has an intelligible graphical user interface for cell counting to assist practical applications. Overall, we expect that the proposed TH+ cell counting tool will promote preclinical PD research by saving time and enabling objective analysis of IHC images.