LIVIVO - The Search Portal for Life Sciences

zur deutschen Oberfläche wechseln
Advanced search

Search results

Result 1 - 10 of total 36

Search options

  1. Article ; Online: Cr-Doped Ge-Core/Si-Shell Nanowire: An Antiferromagnetic Semiconductor.

    Aryal, Sandip / Paudyal, Durga / Pati, Ranjit

    Nano letters

    2021  Volume 21, Issue 4, Page(s) 1856–1862

    Abstract: An antiferromagnet offers many important functionalities such as opportunities for electrical control of magnetic domains, immunity from magnetic perturbations, and fast spin dynamics. Introducing some of these intriguing features of an antiferromagnet ... ...

    Abstract An antiferromagnet offers many important functionalities such as opportunities for electrical control of magnetic domains, immunity from magnetic perturbations, and fast spin dynamics. Introducing some of these intriguing features of an antiferromagnet into a low dimensional semiconductor core-shell nanowire offers an exciting pathway for its usage in antiferromagnetic semiconductor spintronics. Here, using a quantum mechanical approach, we predict that the Cr-doped Ge-core/Si-shell nanowire behaves as an antiferromagnetic semiconductor. The origin of antiferromagnetic spin alignments between Cr is attributed to the superexchange interaction mediated by the p
    Language English
    Publishing date 2021-02-12
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.0c04971
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  2. Book ; Online: Novel Ion Trap Junction Design for Transporting Qubits in a 2D Array

    Nop, Gavin N. / Smith, Jonathan D. H. / Stick, Daniel / Paudyal, Durga

    2023  

    Abstract: Junctions are fundamental elements that support qubit locomotion in two-dimensional ion trap arrays and enhance connectivity in emerging trapped-ion quantum computers. In surface ion traps they have typically been implemented by shaping radio frequency ( ... ...

    Abstract Junctions are fundamental elements that support qubit locomotion in two-dimensional ion trap arrays and enhance connectivity in emerging trapped-ion quantum computers. In surface ion traps they have typically been implemented by shaping radio frequency (RF) electrodes in a single plane to minimize the disturbance to the pseudopotential. However, this method introduces issues related to RF lead routing that can increase power dissipation and the likelihood of voltage breakdown. Here, we propose and simulate a novel two-layer junction design incorporating two perpendicularly rotoreflected linear ion traps. The traps are vertically separated, and create a trapping potential between their respective planes. The orthogonal orientation of the RF electrodes of each trap relative to the other provides perpendicular axes of confinement that can be used to realize transport in two dimensions. While this design introduces manufacturing and operating challenges, as now two separate structures have to be precisely positioned relative to each other in the vertical direction and optical access from the top is obscured, it obviates the need to route RF leads below the top surface of the trap and eliminates the pseudopotential bumps that occur in typical junctions. In this paper the stability of idealized ion transfer in the new configuration is demonstrated, both by solving the Mathieu equation analytically to identify the stable regions and by numerically modeling ion dynamics. Our novel junction layout enhances the flexibility of microfabricated ion trap control to enable large-scale trapped-ion quantum computing.

    Comment: 9 pages
    Keywords Quantum Physics
    Subject code 612 ; 621
    Publishing date 2023-10-11
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  3. Book ; Online: Distinguishing erbium dopants in Y$_2$O$_3$ by site symmetry

    Bhandari, Churna / Şahin, Cüneyt / Paudyal, Durga / Flatté, Michael E.

    \textit{ ab initio} theory of two spin-photon interfaces

    2023  

    Abstract: We present a first-principles study of defect formation and electronic structure of erbium (Er)-doped yttria (Y$_2$O$_3$). This is an emerging material for spin-photon interfaces in quantum information science due to the narrow linewidth optical emission ...

    Abstract We present a first-principles study of defect formation and electronic structure of erbium (Er)-doped yttria (Y$_2$O$_3$). This is an emerging material for spin-photon interfaces in quantum information science due to the narrow linewidth optical emission from Er dopants at standard telecommunication wavelengths and their potential for quantum memories and transducers. We calculate formation energies of neutral, negatively, and positively charged Er dopants and find the charge neutral configuration to be the most stable, consistent with experiment. Of the two substitutional sites of Er for Y, the $C_2$ (more relevant for quantum memories) and $C_{3i}$ (more relevant for quantum transduction), we identify the former as possessing the lowest formation energy. The electronic properties are calculated using the Perdew-Burke-Ernzerhof (PBE) functional along with the Hubbard $U$ parameter and spin-orbit coupling (SOC), which yields a $\sim$ 6 $\mu_B$ orbital and a $\sim$ 3 $\mu_B$ spin magnetic moment, and 11 electrons in the Er $4f$ shell, confirming the formation of charge-neutral Er$^{3+}$. This standard density functional theory (DFT) approach underestimates the band gap of the host and lacks a first-principles justification for $U$. To overcome these issues, we performed screened hybrid functional (HSE) calculations, including a negative $U$ for the $4f$ orbitals, with mixing ($\alpha$) and screening ($w$) parameters. These produced robust electronic features with slight modifications in the band gap and the $4f$ splittings depending on the choice of tuning parameters. We also computed the many-particle electronic excitation energies and compared them with experimental values from photoluminescence.

    Comment: 9 pages, 6 figures
    Keywords Condensed Matter - Materials Science ; Quantum Physics
    Subject code 541
    Publishing date 2023-05-25
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  4. Book ; Online: Accurate Machine Learning Predictions of Coercivity in High-Performance Permanent Magnets

    Bhandari, Churna / Nop, Gavin N. / Smith, Jonathan D. H. / Paudyal, Durga

    2023  

    Abstract: Increased demand for high-performance permanent magnets in the electric vehicle and wind turbine industries has prompted the search for cost-effective alternatives. Nevertheless, the discovery of new magnetic materials with the desired intrinsic and ... ...

    Abstract Increased demand for high-performance permanent magnets in the electric vehicle and wind turbine industries has prompted the search for cost-effective alternatives. Nevertheless, the discovery of new magnetic materials with the desired intrinsic and extrinsic permanent magnet properties presents a significant challenge. Traditional density functional theory (DFT) accurately predicts intrinsic permanent magnet properties such as magnetic moments, magneto-crystalline anisotropy constants, and exchange interactions. However, it cannot compute extrinsic macroscopic properties, such as coercivity ($H_c$), which are influenced by factors like microscopic defects and internal grain structures. Although micromagnetic simulation helps compute $H_c$, it overestimates the values almost by an order of magnitude due to Brown's paradox. To circumvent these limitations, we employ machine learning (ML) methods in an extensive database obtained from experiments, DFT calculations, and micromagnetic modeling. Our novel ML approach is computationally much faster than the micromagnetic simulation program, the mumax$^3$. We successfully utilize it to predict $H_c$ values for materials like cerium-doped $\mathrm{Nd}_2\mathrm{Fe}_{14}\mathrm{B}$, and subsequently compare the predicted values with experimental results. Remarkably, our ML model accurately identifies uniaxial magnetic anisotropy as the primary contributor to $H_c$. With DFT calculations, we predict the Nd-site dependent magnetic anisotropy behavior in $\mathrm{Nd}_2\mathrm{Fe}_{14}\mathrm{B}$, confirming $4f$-site planar and $4g$-site uniaxial to crystalline $c$-direction in good agreement with experiment. The Green's function atomic sphere approximation calculated a Curie temperature ($T_{\rm C}$) for $\mathrm{Nd}_2\mathrm{Fe}_{14}\mathrm{B}$ that also agrees well with experiment.

    Comment: 17 pages, 11 figures
    Keywords Condensed Matter - Materials Science ; Physics - Data Analysis ; Statistics and Probability
    Publishing date 2023-12-04
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  5. Book ; Online: Understanding the origin of magnetocrystalline anisotropy in pure and Fe/Si substituted SmCo5

    Chouhan, Rajiv K. / Pathak, A. K. / Paudyal, D.

    2019  

    Abstract: We report magnetocrystalline anisotropy of pure and Fe/Si substituted SmCo5. The calculations were performed using the advanced density functional theory (DFT) including onsite electron-electron correlation and spin orbit coupling. Si substitution ... ...

    Abstract We report magnetocrystalline anisotropy of pure and Fe/Si substituted SmCo5. The calculations were performed using the advanced density functional theory (DFT) including onsite electron-electron correlation and spin orbit coupling. Si substitution substantially reduces both uniaxial magnetic anisotropy and magnetic moment. Fe substitution with the selective site, on the other hand, enhances the magnetic moment with limited chemical stability. The magnetic hardness of SmCo5 is governed by Sm 4f localized orbital contributions, which get flatten and split with the substitution of Co (2c) with Si/Fe atoms, except the Fe substitution at 3g site. It is also confirmed that Si substitutions favor the thermodynamic stability on the contrary to diminishing the magnetic and anisotropic effect in SmCo5 at either site.
    Keywords Condensed Matter - Materials Science
    Publishing date 2019-12-06
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  6. Book ; Online: Quantum-confined charge transfer that enhances magnetic anisotropy in lanthanum M-type hexaferrites

    Bhandari, Churna / Flatté, Michael E. / Paudyal, Durga

    2021  

    Abstract: Iron-based hexaferrites are critical-element-free permanent magnet components of magnetic devices. Of particular interest is electron-doped M-type hexaferrite i.e., LaFe$_{12}$O$_{19}$ (LaM) in which extra electrons introduced by lanthanum substitution ... ...

    Abstract Iron-based hexaferrites are critical-element-free permanent magnet components of magnetic devices. Of particular interest is electron-doped M-type hexaferrite i.e., LaFe$_{12}$O$_{19}$ (LaM) in which extra electrons introduced by lanthanum substitution of barium/strontium play a key role in uplifting the magnetocrystalline anisotropy. We investigate the electronic structure of lanthanum hexaferrite using a \textit{localized} density functional theory which reproduces semiconducting behavior and identifies the origin of the very large magnetocrystalline anisotropy. Localized charge transfer from lanthanum to the iron at the crystal's $2a$ site produces a narrow $3d_{z^2}$ valence band strongly locking the magnetization along the $c$ axis. The calculated uniaxial magnetic anisotropy energies from fully self-consistent calculations are nearly double the single-shot values, and agree well with available experiments. The chemical similarity of lanthanum to other rare earths suggests that LaM can host for other rare earths possessing non-trivial $4f$ electronic states for, \textit{e.g.,} microwave-optical quantum transduction.

    Comment: 10 pages and 9 figures
    Keywords Condensed Matter - Materials Science
    Subject code 530
    Publishing date 2021-06-22
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  7. Article ; Online: Emergent Ferromagnetism in CaRuO

    Kane, Margaret / Bhandari, Churna / Holtz, Megan E / Balakrishnan, Purnima P / Grutter, Alexander J / Fitzsimmons, Michael / Yang, Chao-Yao / Satpathy, Sashi / Paudyal, Durga / Suzuki, Yuri

    Nano letters

    2024  Volume 24, Issue 8, Page(s) 2567–2573

    Abstract: The boundary between ... ...

    Abstract The boundary between CaRuO
    Language English
    Publishing date 2024-02-17
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.3c04623
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  8. Article ; Online: Magnetostructural behavior in the non-centrosymmetric compound Nd

    Mudryk, Y / Ritter, C / Paudyal, D / Provino, A / Dhar, S K / Manfrinetti, P / Fauth, F / Pecharsky, V K

    Journal of physics. Condensed matter : an Institute of Physics journal

    2019  Volume 31, Issue 26, Page(s) 265801

    Abstract: A systematic study of the physical properties and microscopic magnetism of ... ...

    Abstract A systematic study of the physical properties and microscopic magnetism of Nd
    Language English
    Publishing date 2019-03-20
    Publishing country England
    Document type Journal Article
    ZDB-ID 1472968-4
    ISSN 1361-648X ; 0953-8984
    ISSN (online) 1361-648X
    ISSN 0953-8984
    DOI 10.1088/1361-648X/ab1192
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

  9. Article ; Online: Crystal, magnetic, calorimetric and electronic structure investigation of GdScGe

    Guillou, F / Pathak, A K / Hackett, T A / Paudyal, D / Mudryk, Y / Pecharsky, V K

    Journal of physics. Condensed matter : an Institute of Physics journal

    2017  Volume 29, Issue 48, Page(s) 485802

    Abstract: Experimental investigations of crystal structure, magnetism and heat capacity of compounds in the pseudoternary GdScGe-GdScSb system combined with density functional theory projections have been employed to clarify the interplay between the crystal ... ...

    Abstract Experimental investigations of crystal structure, magnetism and heat capacity of compounds in the pseudoternary GdScGe-GdScSb system combined with density functional theory projections have been employed to clarify the interplay between the crystal structure and magnetism in this series of RTX materials (R  =  rare-earth, [Formula: see text]  =  transition metal and X  =  p-block element). We demonstrate that the CeScSi-type structure adopted by GdScGe and CeFeSi-type structure adopted by GdScSb coexist over a limited range of compositions [Formula: see text]. Antimony for Ge substitutions in GdScGe result in an anisotropic expansion of the unit cell of the parent that is most pronounced along the c axis. We believe that such expansion acts as the driving force for the instability of the double layer CeScSi-type structure of the parent germanide. Extensive, yet limited Sb substitutions [Formula: see text] lead to a strong reduction of the Curie temperature compared to the GdScGe parent, but without affecting the saturation magnetization. With a further increase in Sb content, the first compositions showing the presence of the CeFeSi-type structure of the antimonide, [Formula: see text], coincide with the appearance of an antiferromagnetic phase. The application of a finite magnetic field reveals a jump in magnetization toward a fully saturated ferromagnetic state. This antiferro-ferromagnetic transformation is not associated with a sizeable latent heat, as confirmed by heat capacity measurements. The electronic structure calculations for [Formula: see text] indicate that the key factor in the conversion from the ferromagnetic CeScSi-type to the antiferromagnetic CeFeSi-type structure is the disappearance of the induced magnetic moments on Sc. For the parent antimonide, heat capacity measurements indicate an additional transition below the main antiferromagnetic transition.
    Language English
    Publishing date 2017-11-09
    Publishing country England
    Document type Journal Article
    ZDB-ID 1472968-4
    ISSN 1361-648X ; 0953-8984
    ISSN (online) 1361-648X
    ISSN 0953-8984
    DOI 10.1088/1361-648X/aa93aa
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

  10. Article ; Online: Non-hysteretic first-order phase transition with large latent heat and giant low-field magnetocaloric effect.

    Guillou, F / Pathak, A K / Paudyal, D / Mudryk, Y / Wilhelm, F / Rogalev, A / Pecharsky, V K

    Nature communications

    2018  Volume 9, Issue 1, Page(s) 2925

    Abstract: First-order magnetic transitions (FOMTs) with a large discontinuity in magnetization are highly sought in the development of advanced functional magnetic materials. Isosymmetric magnetoelastic FOMTs that do not perturb crystal symmetry are especially ... ...

    Abstract First-order magnetic transitions (FOMTs) with a large discontinuity in magnetization are highly sought in the development of advanced functional magnetic materials. Isosymmetric magnetoelastic FOMTs that do not perturb crystal symmetry are especially rare, and only a handful of material families, almost exclusively transition metal-based, are known to exhibit them. Yet, here we report a surprising isosymmetric FOMT in a rare-earth intermetallic, Eu
    Language English
    Publishing date 2018-07-26
    Publishing country England
    Document type Journal Article ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-018-05268-4
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

To top