55 research outputs found
Improved resistance to water poisoning of Pd/CeO2 monolithic catalysts by heat treatment for ozone decomposition
No full textDurability is a crucial requirement in heterogeneous catalysis; however, many catalysts suffer from severe deactivation in humid conditions due to water poisoning. Ozone, as a significant air pollutant, should be efficiently removed through catalytic decomposition, making it imperative to develop a water-tolerant monolithic catalyst for practical air purification. In this study, we present highly durable Pd/CeO2 monolithic catalysts resistant to water poisoning achieved through a simple heat treatment of the ceria support. The heat treatment controlled the ceria surface properties, including oxygen vacancy defects, surface oxygen, and basicity, thereby improving resistance to water poisoning. When Pd/CeO2 monolithic catalysts were used in bench-scale ozone decomposition under humid conditions, the catalyst heat-treated at 900 degrees C exhibited superior performance without experiencing deactivation due to water poisoning. Modulating the ceria surface properties plays a pivotal role in enhancing water resistance, and heat-treated Pd/CeO2 monolithic catalysts stand as a promising candidate for practical ozone decomposition in air purification applications.
Scaling of transition temperature and CuO2 plane buckling in the cuprate superconductors
No full textSpin torques and anomalous velocity in spin textures induced by fast electron injection from topological ferromagnets: The role of gauge fields
No full textA new method for analysing magnetization dynamics in spin textures under the
influence of fast electron injection from topological ferromagnetic sources
such as Dirac half metals has been proposed. These electrons, traveling at a
velocity with a non-negligible value of (where c is the speed of
light), generate a non-equilibrium magnetization density in the spin-texture
region, which is related to an electric dipole moment via relativistic
interactions. When this resulting dipole moment interacts with gauge fields in
the spin-texture region, an effective field is created that produces spin
torques. These torques, like spin-orbit torques that occur when electrons are
injected from a heavy metal into a ferromagnet, can display both damping-like
and anti-damping-like properties. Finally, we demonstrate that such an
interaction between the dipole moment and the gauge field introduces an
anomalous velocity that can contribute to transverse electrical conductivity in
the spin texture in a way comparable to the topological Hall effect
Magnetization dynamics in skyrmions due to high-speed carrier injections from Dirac half-metals
No full textRecent developments in the magnetization dynamics in spin textures, particularly skyrmions, offer promising new directions for magnetic storage technologies and spintronics. Skyrmions, characterized by their topological protection and efficient mobility at low current density, are increasingly recognized for their potential applications in next-generation logic and memory devices. This study investigates the dynamics of skyrmion magnetization, focusing on the manipulation of their topological states as a basis for bitwise data storage through a modified Landau-Lifshitz-Gilbert equation (LLG). We introduce spin-polarized electrons from a topological ferromagnet that induce an electric dipole moment that interacts with the electric gauge field within the skyrmion domain. This interaction creates an effective magnetic field that results in a torque that can dynamically change the topological state of the skyrmion. In particular, we show that these torques can selectively destroy and create skyrmions, effectively writing and erasing bits, highlighting the potential of using controlled electron injection for robust and scalable skyrmion-based data storage solutions
Atomistic Spin Dynamic Method with both Damping and Moment of Inertia Effects Included from First Principles
No full textWe consider spin dynamics for implementation in an atomistic framework and we address the feasibility of capturing processes in the femtosecond regime by inclusion of moment of inertia. In the spirit of an s-d-like interaction between the magnetization and electron spin, we derive a generalized equation of motion for the magnetization dynamics in the semiclassical limit, which is nonlocal in both space and time. Using this result we retain a generalized Landau-Lifshitz-Gilbert equation, also including the moment of inertia, and demonstrate how the exchange interaction, damping, and moment of inertia, all can be calculated from first principles.</p
Silicon-doped icosahedral, cuboctahedral, and decahedral clusters of aluminum
No full text学術論文 (Article)journal articl
First principles calculations of magnetism, dielectric properties and spin-phonon coupling in double perovskite Bi2CoMnO6
No full textFirst principles electronic structure calculations have been performed for the double perovskite Bi2CoMnO6 in its non-centrosymmetric polar state using the generalized gradient approximation plus the Hubbard U approach. We find that the ferromagnetic state is more favored compared to the ferrimagnetic state with both Co and Mn in high spin states. The calculated dynamical charge tensors are anisotropic reflecting a low-symmetry structure of the compound. The magnetic structure dependent phonon frequencies indicate the presence of a weak spin-phonon coupling. Using the Berry phase method, we obtain a spontaneous ferroelectric polarization of 5.88 mu C cm(-2), which is close to the experimental value observed for a similar compound, Bi2NiMnO6.</p
Engineering Multiferroism in CaMnO3
No full textpeer reviewedStructural instabilities of CaMnO3 are investigated from first principles. We point out that, on top of a strong antiferrodistortive instability responsible for its orthorhombic ground state, the cubic perovskite structure of CaMnO3 also exhibits a weak ferroelectric instability. Although ferroelectricity is suppressed by antiferrodistortive motions, we show that it can be favored using strain or chemical engineering in order to make CaMnO3 multiferroic. We finally highlight that the ferroelectric instability of CaMnO3 is Mn-dominated. This illustrates that, contrary to common belief, ferroelectricity and magnetism are not necessarily exclusive but can be driven by the same cation
Surface-oxygen-passivation driven large anomalous Hall conductivity (AHC) in nitride MXenes: Can AHC be a tool to determine functional groups in 2D ferro(i)magnets?
No full textIdentifying the existence of specific functional groups in MXenes is a
difficult topic that has perplexed researchers for a long time. We show in this
paper that in the case of magnetic MXenes, the magneto-transport properties of
the material provide an easy solution. One of the fascinating properties that
MXenes offer is the realization of intrinsic ferromagnetism which is important
for two-dimensional (2D) materials family. The previous reports have only made
a few statements on some MXenes citing its usefulness for spintronics related
applications. Here, using first-principle calculations we have examined the
actual magneto-transport phenomena in MXenes family. We have considered all
possible combinations of 3\textit{d} transition metals ( and )
and nitride based functionalized and ) MXenes, .
The intrinsic anomalous Hall effect is investigated in and based
MXenes as the compounds possess ground state stable ferromagnetic solutions. We
demonstrate that intrinsic Anomalous Hall conductivity (AHC) can be used to
identify the functional groups in MXenes.
Additionally, half-metallic features of these ferromagnetic MXenes make them
potential candidates for varieties of applications such as in logic and memory
devices, quantum computations, spintronics etc. The maximum anomalous Hall
conductivity (AHC) at Fermi energy, , is found in case of (470
) which is attributed to the presence of avoided band crossing and larger
density of states. Together, when considered all the studied systems, the AHC
can be above 2500 within 0.25 . Our findings could be
useful not only in guiding the experimentalists by considering AHC as a simple
tool in determining the functional groups in 2D ferro(i)magnets, also, it could
be useful in designing memory device with negligible stray fields.Comment: 19 pages and 6 figures (including TOC
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