Search results for "Ferro"
showing 10 items of 2451 documents
Monte Carlo studies ofd= 2 Ising strips with long-range boundary fields
2000
A two-dimensional Ising model with nearest-neighbour ferromagnetic exchange confined in a strip of width L between two parallel boundaries is studied by Monte Carlo simulations. `Free' boundaries are considered with unchanged exchange interactions at the boundary but long-range boundary fields of the form H (n ) = ? h [n -3 - (L - n + 1) -3 ], where n = 1, 2, ... ,L labels the rows across the strip. In the case of competing fields and L , the system exhibits a critical wetting transition of a similar type as in the well studied case of short-range boundary fields. At finite L , this wetting transition is replaced by a (rounded) interface localization-delocalization transition at Tc (h , L )…
Critical behavior in quantum spin chains with composite spin
1989
Composite spin models are constructed such that, by varying two parameters, they interpolate between the spin-(1/2 antiferromagnetic Heisenberg chain and a number of spin-1 models. These include the usual Heisenberg model, the integrable spin-1 model, and the model with an exact valence-bond ground state. Finite-chain calculations are performed on the composite spin model to study its criticality, and to find if the integrable spin-1 model is a multicritical point with a finite gap generated away from it. We find indications for an extended gapless region.
Toward multifunctional molecular cells for quantum cellular automata: exploitation of interconnected charge and spin degrees of freedom
2021
We discuss the possibility of using mixed-valence (MV) dimers comprising paramagnetic metal ions as molecular cells for quantum cellular automata (QCA). Thus, we propose to combine the underlying idea behind the functionality of QCA of using the charge distributions to encode binary information with the additional functional options provided by the spin degrees of freedom. The multifunctional ('smart') cell is supposed to consist of multielectron MV d(n)-d(n+1)-type (1 ≤ n ≤ 8) dimers of transition metal ions as building blocks for composing bi-dimeric square planar cells for QCA. The theoretical model of such a cell involves the double exchange (DE), Heisenberg-Dirac-Van Vleck (HDVV) excha…
Dynamic spin-triplet order induced by alternating electric fields in superconductor-ferromagnet-superconductor Josephson junctions
2021
Dynamic states offer extended possibilities to control the properties of quantum matter. Recent efforts are focused on studying the ordered states which appear exclusively under the time-dependent drives. Here we demonstrate a class of systems which feature dynamic spin-triplet superconducting order stimulated by the alternating electric field. The effect is based on the interplay of ferromagnetism, interfacial spin-orbital coupling (SOC) and the condensate motion driven by the field, which converts hidden static p-wave order, produced by the joint action of the ferromagnetism and the SOC, into dynamical s-wave equal-spin triplet correlations. We demonstrate that the critical current of Jos…
Optimized factor of merit of the magneto-optical Kerr effect of ferromagnetic thin films
2000
This paper deals with the optimization of the factor of merit of the magneto-optical Kerr effect of a resonant multilayer cavity including a ferromagnetic film. This optimization is of interest in the context of optical storage technology. Using numerical simulations based on the Green's dyadic technique, we discuss a route to obtain magneto-optical multilayers with a vanishing ellipticity and factors of merit (with respect to the bulk magnetic material) larger than 3 on a broad range of wavelengths, significantly higher than the actual state of the art.
Spin-order dependent anomalous Hall effect and magneto-optical effect in the noncollinear antiferromagnets Mn3XN with X=Ga , Zn, Ag, or Ni
2019
The anomalous Hall effect (AHE) and the magneto-optical effect (MOE) are two prominent manifestations of time-reversal symmetry breaking in magnetic materials. Noncollinear antiferromagnets (AFMs) have recently attracted a lot of attention owing to the potential emergence of exotic spin orders on geometrically frustrated lattices, which can be characterized by corresponding spin chiralities. By performing first-principles density functional calculations together with group-theory analysis and tight-binding modeling, here we systematically study the spin-order dependent AHE and MOE in representative noncollinear AFMs ${\mathrm{Mn}}_{3}X\mathrm{N}\phantom{\rule{4pt}{0ex}}(X=\mathrm{Ga}$, Zn, …
Stabilizing and increasing the magnetic moment of half-metals: The role of Li in half-HeuslerLiMnZ(Z=N,P,Si)
2015
Due to their similarities to metastable zinc-blende half-metals, we systematically examined the half-Heusler compounds $\ensuremath{\beta}\text{-LiMn}Z$ ($Z=\text{N},\text{P}$ and Si) for their electronic, magnetic, and stability properties at optimized lattice constants and strained lattice constants that exhibit half-metallic properties. We also report the other phases of the half-Heusler structure ($\ensuremath{\alpha}$ and $\ensuremath{\gamma}$ phases), but they are unlikely to be grown. The magnetic moments of these stable Li-based compounds are expected to reach as high as $4{\ensuremath{\mu}}_{\mathrm{B}}$ per unit cell when $Z=\text{Si}$ and $5{\ensuremath{\mu}}_{\mathrm{B}}$ per un…
Roles of chiral renormalization on magnetization dynamics in chiral magnets
2018
In metallic ferromagnets, the interaction between local magnetic moments and conduction electrons renormalizes parameters of the Landau-Lifshitz-Gilbert equation such as the gyromagnetic ratio and the Gilbert damping, and makes them dependent on the magnetic configurations. Although the effects of the renormalization for nonchiral ferromagnets are usually minor and hardly detectable, we show that the renormalization does play a crucial role for chiral magnets. Here the renormalization is chiral and as such we predict experimentally identifiable effects on the phenomenology of magnetization dynamics. In particular, our theory for the self-consistent magnetization dynamics of chiral magnets a…
Dynamical and current-induced Dzyaloshinskii-Moriya interaction: Role for damping, gyromagnetism, and current-induced torques in noncollinear magnets
2020
Both applied electric currents and magnetization dynamics modify the Dzyaloshinskii-Moriya interaction (DMI), which we call current-induced DMI (CIDMI) and dynamical DMI (DDMI), respectively. We report a theory of CIDMI and DDMI. The inverse of CIDMI consists in charge pumping by a time-dependent gradient of magnetization ${\ensuremath{\partial}}^{2}\mathbit{M}(\mathbit{r},t)/\ensuremath{\partial}\mathbit{r}\ensuremath{\partial}t$, while the inverse of DDMI describes the torque generated by ${\ensuremath{\partial}}^{2}\mathbit{M}(\mathbit{r},t)/\ensuremath{\partial}\mathbit{r}\ensuremath{\partial}t$. In noncollinear magnets, CIDMI and DDMI depend on the local magnetization direction. The re…
An antidamping spin–orbit torque originating from the Berry curvature
2014
Magnetization switching at the interface between ferromagnetic and paramagnetic metals, controlled by current-induced torques, could be exploited in magnetic memory technologies. Compelling questions arise regarding the role played in the switching by the spin Hall effect in the paramagnet and by the spin-orbit torque originating from the broken inversion symmetry at the interface. Of particular importance are the antidamping components of these current-induced torques acting against the equilibrium-restoring Gilbert damping of the magnetization dynamics. Here, we report the observation of an antidamping spin-orbit torque that stems from the Berry curvature, in analogy to the origin of the …