One-dimensional Magnetic Chain Research Articles

Effects of the Dzyaloshinskii-Moriya interaction on the Fermi-Pasta-Ulam behavior in a magnetic system

We study the behavior of nonlinear spin motion in one-dimensional magnetic chain models. We explore how the various parameters affect the phase transitions between linear and nonlinear behaviors both with and without the Dzyaloshinskii-Moriya interaction (DMI). A Fourier analysis method is employed to investigate the modes in the structure with DMI. In all cases, we find that uniaxial anisotropy is necessary for the Fermi-Pasta-Ulam effect to appear. We investigate the DMI influence through the use of phase diagrams that examine the transitions between the three fundamental states: linear, Fermi-Pasta-Ulam, and ergodic. The DMI does make significant changes in these phase diagrams because it allows for additional routes for the distribution of energy.

Tailoring the phase transition from topological superconductor to trivial superconductor induced by magnetic textures of a spin chain on a p -wave superconductor

We theoretically investigate the phase transition from a nontrivial topological $p$-wave superconductor to a trivial $s$-wave-like superconducting phase through a gapless phase, driven by different magnetic textures as a one-dimensional spin-chain impurity, e.g., Bloch-type, in-plane, and out-of-plane N\'eel-type spin chains, etc. In our proposal, the chain of magnetic impurities is placed on a spin-triplet $p$-wave superconductor where we obtain numerically as well as analytically an effective $s$-wave-like pairing due to spin rotation, resulting in gradual destruction of the Majorana zero modes present in the topological superconducting phase. In particular, when the impurity spins are antiferromagnetically aligned, i.e., spiral wave vector ${G}_{\mathrm{s}}=\ensuremath{\pi}$, the system becomes an effective $s$-wave superconductor without Majorana zero modes in the local density of states. The Shiba bands, on the other hand, formed due to the overlapping of Yu-Shiba-Rusinov states play a crucial role in this topological to trivial superconductor phase transition, confirmed by the sign change in the minigap within the Shiba bands. We also characterize this topological phase transition via gap closing and winding number analysis. Moreover, interference of the Shiba bands exhibiting oscillatory behavior within the superconducting gap $\ensuremath{-}{\mathrm{\ensuremath{\Delta}}}_{p}$ to ${\mathrm{\ensuremath{\Delta}}}_{p}$, as a function of ${G}_{s}$, also reflects an important evidence for the formation of an effective $s$-wave pairing. Such oscillation is absent in the $p$-wave regime. We also analyze the case of two-dimensional $p$-wave superconductor hosting Majorana edge modes (in absence of any magnetic chain) and show that initially Majorana zero modes (in presence of one-dimensional magnetic chain) can hybridize with such Majorana edge modes. Interestingly, in the topological regime with a fixed ${G}_{s}$ value, the Mazorana zero modes survive at the ends of the magnetic chain even when the Majorana edge states disappear at some critical value of the chemical potential and exchange coupling strength.

Indeno[2,1-a]fluorene-11,12-dione Radical Anions: Synthesis, Characterization, and Properties.

The one-electron reduction of indeno[2,1-a]fluorene-11,12-dione (IF) with various alkali metals prepare the radical anion salts. The data about different structures, properties, and characterization was obtained by single-crystal X-ray diffraction, electron paramagnetic resonance (EPR) spectroscopy, superconducting quantum interference device (SQUID) measurements, and physical property measurement system (PPMS). Compound IF.- K+ (18-c-6) is regarded as a one-dimensional magnetic chain through C-H⋅⋅⋅C interaction. Theoretical calculations and magnetic results showed that [IF.- K+ (15-c-5)]2 is a dimer with an open-shell ground state. Compounds IF.- Na+ (15-c-5) and IF.- K+ (cryptand) are monoradical anion salts: IF2 .- Li+ possesses unique π-stack structure with an interplanar separation less than 3.46 Å, making it a semiconductor (δRT =1.9×10-4 S ⋅ cm-1 ). This work gives insights into multifunctional radical anions, and describes the design and development of different functional radicals.

The catenation of a singlet diradical dication and modulation of diradical character by metal coordination.

A singlet bis(triarylamine) diradical dication and its zigzag 1D magnetic chain catenated by silver cations were isolated and characterized by single-crystal X-ray crystallography, EPR spectroscopy, SQUID measurements, cyclic voltammetry, and UV-Vis-NIR absorption spectroscopy in conjunction with DFT calculations. The ΔEOS-T has significantly changed due to the coordination of carbonyls (Lewis base) with Ag+ (Lewis acid), revealing that the diradical character can be modulated by Lewis acid-base coordination and interchain intermolecular coupling interactions.

Spin polarization in an ac-driven magnetic material with vanishing net magnetization: a new proposal

In this work, we address the fundamental question of whether a magnetic material having zero net magnetization can produce polarized spin current from a completely unpolarized one. Common wisdom suggests that this is not possible, but if we break the symmetry in hopping integrals in different segments of the magnetic sample, then a finite possibility of getting polarized spin current is established. To substantiate this fact, we consider a one-dimensional magnetic chain with vanishing net magnetization where one part of the chain is subjected to an ac electric field, keeping the other part free. The ac field, introduced through Peierls substitution, modulates the hopping integrals yielding a misalignment of up and down spin channels, which is the primary requirement to get finite spin polarization. Simulating the system within a tight-binding framework, we compute spin-dependent transmission probabilities using the well-known Green’s function prescriptionand determine junction currents following the Landauer–Büttiker formalism. Our analysis may shed some light on designing spin-polarized devices using driven magnetic materials with vanishing net magnetization.

Chiral symmetry and scale invariance breaking in spin chains

The effects of the Dzyaloshinsky-Moriya interaction on finite size one-dimensional (1D) magnetic chains are investigated as a function of their length. The magnetic configuration the system adopts for varying boundary conditions are explored analytically, which leads to the appearance of chiral configurations that play a crucial role. The coercive and exchange bias fields show an unexpected chain length dependence, caused by the boundary conditions and by chiral symmetry breaking, which in turn leads to the breakdown of scale-invariance. Our treatment yields results in agreement with experimental evidence and ongoing research on phthalocyanine iron chains bonded to hydrogen.

Observation of a Large Magnetic Anisotropy and a Field-Induced Magnetic State in SrCo(VO4)(OH): A Structure with a Quasi One-Dimensional Magnetic Chain.

A new member of the descloizite family, a cobalt vanadate, SrCo(VO4)(OH), has been synthesized as large single crystals using high-temperature and high-pressure hydrothermal methods. SrCo(VO4)(OH) crystallizes in the orthorhombic crystal system in space group P212121 with the following unit cell parameters: a = 6.0157(2) Å, b = 7.645(2) Å, c = 9.291(3) Å, V = 427.29(2) Å3, and Z = 4. It contains one-dimensional Co-O-Co chains of edge-sharing CoO6 octahedra along the a-axis connected to each other via VO4 tetrahedra along the b-axis forming a three-dimensional structure. The magnetic susceptibility of SrCo(VO4)(OH) indicates an antiferromagnetic transition at 10 K as well as unusually large spin orbit coupling. Single-crystal magnetic measurements in all three main crystallographic directions displayed a significant anisotropy in both temperature- and field-dependent data. Single-crystal neutron diffraction at 4 K was used to characterize the magnetically ordered state. The Co2+ magnetic spins are arranged in a staggered configuration along the chain direction, with a canting angle that follows the tipping of the CoO6 octahedra. The net magnetization along the chain direction, resulting in ferromagnetic coupling of the a-axis spin components in each chain, is compensated by an antiferromagnetic interaction between nearest neighbor chains. A metamagnetic transition appears in the isothermal magnetization data at 2 K along the chain direction, which seems to correspond to a co-alignment of the spin directions of the nearest neighbor chain. We propose a phenomenological spin Hamiltonian that describes the canted spin configuration of the ground state and the metamagnetic transition in SrCo(VO4)(OH).

Highly symmetric random one-dimensional spin models

The interplay of disorder and interactions is a challenging topic of condensed matter physics, where correlations are crucial and exotic phases develop. In one spatial dimension, a particularly successful method to analyze such problems is the strong-disorder renormalization group (SDRG). This method, which is asymptotically exact in the limit of large disorder, has been successfully employed in the study of several phases of random magnetic chains. Here we develop an SDRG scheme capable to provide in-depth information on a large class of strongly disordered one-dimensional magnetic chains with a global invariance under a generic continuous group. Our methodology can be applied to any Lie-algebra valued spin Hamiltonian, in any representation. As examples, we focus on the physically relevant cases of SO(N) and Sp(N) magnetism, showing the existence of different randomness-dominated phases. These phases display emergent SU(N) symmetry at low energies and fall in two distinct classes, with meson-like or baryon-like characteristics. Our methodology is here explained in detail and helps to shed light on a general mechanism for symmetry emergence in disordered systems.

A Main-Group Element Radical Based One-Dimensional Magnetic Chain.

The first main-group element radical based one-dimensional magnetic chain (1K)n was realized by one-electron reduction of the pyridinyl functionalized borane 1 with elemental potassium in THF in the absence of 18-crown-6 (18-c-6). The electron spin density of (1K)n mainly resides at the boron centers with a considerable contribution from central benzene and pyridine moieties. The spin centers exhibit an antiferromagnetic interaction as demonstrated by magnetic measurements and theoretical calculations. In contrast, the reduction in the presence of 18-c-6 afforded the separated radical anion salt 1K(Crown), in which the potassium cation was trapped by THF and 18-c-6 molecules. Further one-electron reduction of 1K(Crown) and (1K)n led to the diamagnetic monomer and polymer, respectively.

One-dimensional magnetic chain composed of CuII and polychlorinated dipyridylphenylmethyl radical: temperature-dependent Jahn-Teller distortion correlated to π-conjugation and magnetic properties.

The one-dimensional coordination polymer composed of CuII and an organic radical bisPyTM displayed temperature dependent Jahn-Teller distortion, which is correlated to the π-conjugation mode at the ligand as well as the magnetic properties. The ferromangetic bisPyTM-CuII interaction was enhanced by the reorientation of the CuII dx2-y2 orbital at low temperature.

Exploration of Fermi-Pasta-Ulam Behavior in a Magnetic System.

We study nonlinear spin motion in one-dimensional magnetic chains. We find significant differences from the classic Fermi-Pasta-Ulam (FPU) problem examining nonlinear elastic motion in a chain. We find that FPU behavior, the transfer of energy among low order eigenmodes, does not occur in magnetic systems with only exchange and external fields, but does exist if a uniaxial anisotropy is also present. The FPU behavior may be altered or turned off through the magnitude and orientation of an external magnetic field. A realistic micromagnetic model shows such behavior could be measurable.

Tunable evolutions of shock absorption and energy partitioning in magnetic granular chains

In this paper, we investigate the tunable characteristics of shock waves propagating in one-dimensional magnetic granular chains at various chain lengths and magnetic flux densities. According to the Hertz contact theory and Maxwell principle, a discrete element model with coupling elastic and field-induced interaction potentials of adjacent magnetic grains is proposed. We also present hard-sphere approximation analysis to describe the energy partitioning features of magnetic granular chains. The results demonstrate that, for a fixed magnetic field strength, when the chain length is greater than two times of the wave width of the solitary wave, the chain length has little effect on the output energy of the system; for a fixed chain length, the shock absorption and energy partitioning features of magnetic granular chains are remarkably influenced by varying magnetic flux densities. This study implies that the magnetic granular chain is potential to construct adaptive shock absorption components for impulse mitigation.

A Self-consistent Approach Applied to the Ferro and Antiferromagnetism of Nanotubes

We employ a self-consistent simulation approach based on mean field theory to investigate the physical properties of both ferromagnetic and antiferromagnetic nanotubes. At the beginning, dipole-dipole interaction is neglected to facilitate theoretical analysis. Due to the geometric shape of the nanotubes and the magnetic uniaxial anisotropy, the spins are found always ordering parallel to the longitudinal axis of the nanotubes, no matter the external magnetic field is absent or applied along the axis, showing a typical ferromagnetic and antiferromagnetic characters. This peculiar feature allows us to build the one-dimensional magnetic chain models. Consequently, the results obtained with our theoretical models and numerical approach are exactly identical, manifesting the correctness of the new simulation approach. Finally, the dipole-dipole interaction is taken into account. It is very interesting to find that a very weak dipole-dipole interaction is able to make the spins align mainly along the longitudinal axis, though they tilt inwards or outwards slightly and symmetrically.

Spin filter for arbitrary spins by substrate engineering

We design spin filters for particles with potentially arbitrary spin using a one-dimensional periodic chain of magnetic atoms as a quantum device. Describing the system within a tight-binding formalism we present an analytical method to unravel the analogy between a one-dimensional magnetic chain and a multi-strand ladder network. This analogy is crucial, and is subsequently exploited to engineer gaps in the energy spectrum by an appropriate choice of the magnetic substrate. We obtain an exact correlation between the magnitude of the spin of the incoming beam of particles and the magnetic moment of the substrate atoms in the chain desired for opening up of a spectral gap. Results of spin polarized transport, calculated within a transfer matrix formalism, are presented for particles having half-integer as well as higher spin states. We find that the chain can be made to act as a quantum device which opens a transmission window only for selected spin components over certain ranges of the Fermi energy, blocking them in the remaining part of the spectrum. The results appear to be robust even when the choice of the substrate atoms deviates substantially from the ideal situation, as verified by extending the ideas to the case of a ‘spin spiral’. Interestingly, the spin spiral geometry, apart from exhibiting the filtering effect, is also seen to act as a device flipping spins—an effect that can be monitored by an interplay of the system size and the period of the spiral. Our scheme is applicable to ultracold quantum gases, and might inspire future experiments in this direction.

Higher-dimensional Wannier functions of multiparameter Hamiltonians

When using Wannier functions to study the electronic structure of multi-parameter Hamiltonians $H^{(\boldsymbol k,\bf \lambda)}$ carrying a dependence on crystal momentum $\boldsymbol k$ and an additional periodic parameter $\bf\lambda$, one usually constructs several sets of Wannier functions for a set of values of $\bf\lambda$. We present the concept of higher dimensional Wannier functions (HDWFs), which provide a minimal and accurate description of the electronic structure of multi-parameter Hamiltonians based on a single set of HDWFs. The obstacle of non-orthogonality of Bloch functions at different $\bf\lambda$ is overcome by introducing an auxiliary real space, which is reciprocal to the parameter $\bf\lambda$. We derive a generalized interpolation scheme and emphasize the essential conceptual and computational simplifications in using the formalism, for instance, in the evaluation of linear response coefficients. We further implement the necessary machinery to construct HDWFs from ab initio within the full-potential linearized augmented plane-wave method (FLAPW). We apply our implementation to accurately interpolate the Hamiltonian of a one-dimensional magnetic chain of Mn atoms in two important cases of $\bf\lambda$: (i) the spin-spiral vector $\boldsymbol q$, and (ii) the direction of the ferromagnetic magnetization $\hat{\boldsymbol m}$. Using the generalized interpolation of the energy, we extract the corresponding values of magneto-crystalline anisotropy energy, Heisenberg exchange constants, and spin stiffness, which compare very well with the values obtained from direct first principles calculations. For toy models we demonstrate that the method of HDWFs can also be used in applications such as the virtual crystal approximation, ferroelectric polarization and spin torques.

Odd-frequency pairing in topological superconductivity in a one-dimensional magnetic chain

A chain of magnetic atoms with non-collinear spin configuration on a superconductor is a promising new system that can host Majorana Fermions (MFs). In this study, we clarify that in the presence of MFs, an odd-frequency Cooper pair is generated at the edge of the chain. Furthermore, it is revealed that this feature is robust against the distance between magnetic atoms. We also elucidate the close relationship between the pair amplitude of the odd-frequency pair, the parity of the wave function, and the direction of the MF spin. If Rashba-type spin-orbit coupling is included, MFs can be realized even in a collinear alignment of magnetic atoms, $i.e.$, in a ferromagnetic or anti-ferromagnetic chain on a superconductor. Then, the odd-frequency pairing is generated at the edge, similar to the non-collinear case. Based on our results, it can be concluded that the detection of the zero energy peak of the local density of states by scanning tunneling microscopy at the edge of the magnetic chain is strong evidence for the generation of odd-frequency pairing.

Long-distance relationship

Photons immediately spring to mind when we talk about long-distance entanglement. But the spins at the ends of one-dimensional magnetic chains can be entangled over large distances too — providing a solid-state alternative for quantum communication protocols.

Entanglement in the Quantum Phase Transition of the Half-Integer Spin One-Dimensional Heisenberg Model

We use the Bethe’s ansatz method to study the entanglement of spinons in the quantum phase transition of half integer spin one-dimensional magnetic chains known as quantum wires. We calculate the entanglement in the limit of the number of particles . We obtain an abrupt change in the entanglement next the quantum phase transition point of the anisotropy parameter from the gapped phase to gapless phase .

Helical order in one-dimensional magnetic atom chains and possible emergence of Majorana bound states

We theoretically obtain the phase diagram of localized magnetic impurity spins arranged in a one-dimensional chain on top of a one- or two-dimensional electron gas with Rashba spin-orbit coupling. The interactions between the spins are mediated by the Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism through the electron gas. Recent work predicts that such a system may intrinsically support topological superconductivity when a helical spin-density wave is formed in the spins, and superconductivity is induced in the electron gas. We analyze, using both analytical and numerical techniques, the conditions under which such a helical spin state is stable in a realistic situation in the presence of disorder. We show that it becomes unstable towards the formation of (anti) ferromagnetic domains if the disorder in the impurity spin positions $\delta R$ becomes comparable with the Fermi wave length. We also examine the stability of the helical state against Gaussian potential disorder in the electronic system using a diagrammatic approach. Our results suggest that in order to stabilize the helical spin state, and thus the emergent topological superconductivity, a sufficiently strong Rashba spin-orbit coupling, giving rise to Dzyaloshinskii-Moriya interactions, is required.

A general strategy for one-step fabrication of one-dimensional magnetic nanoparticle chains based on laser ablation in liquid

Assembly of one-dimensional (1D) magnetic nanoparticle (NP) chains is attractive due to considerable technical demand in new materials and devices. Conventional assemblies are usually divided into two steps: one is the synthesis of NPs and the other is the fabrication of 1D NP chains. Here, we demonstrate a general strategy for fabricating 1D magnetic NP chains within one step, i.e. the magnetic field assisted laser ablation in liquid (MF-LAL), which combines NPs’ synthesis and 1D chains’ fabrication within one step. This is a green and facile LAL-based approach. Using this technique, we assemble 1D chains of submicron cobalt carbide spheres, which are ferromagnetic with anomalous giant magnetizations of 232 emu g−1 at room temperature, the highest reported so far for cobalt-based magnetic nanomaterials. The blocking temperature of the chains is more than 300 K, which is ascribed to the anisotropy of the configuration. We establish a theoretical model to pursue the fabrication of 1D magnetic NP chains, in which the basic physics and chemistry involved in the MF-LAL fabrication are discussed. These findings can guide researchers choosing interesting target and liquid for the assembly of 1D magnetic NP chains for the purpose of fundamental research and potential applications.