One-dimensional Ferromagnetic Chain Research Articles

Magnetic transition of 1D ferromagnetic catalysts during the NO electroreduction

Exploration of magnetic phase transitions during electrochemical processes is of great importance for rational design of supported magnetic-metal electrocatalysts. Herein, we systematically investigated the magnetic transition between ferromagnetism (FM) and anti-ferromagnetism (AFM) in one-dimensional ferromagnetic Co chain supported on graphene (Co4N8-gra) during NO electroreduction (NORR) process, focusing on the impact of potential and acidity on the catalytic property and magnetic transition. A combination of catalytic kinetics calculations and microkinetic simulations reveals that the Co4N8-gra exhibits excellent NH3 selectivity and thermal stability. In the implicit solvent model, the general reaction follows optimal pathway: * + NO(g) → *NO → *HNO → *H2NO → *H2NOH → *NH2 → *NH3 → * + NH3, with the potential-determining step (PDS) identified as *NO → *HNO. In acidic solvent, the magnetic transitions follow the pathway (FM → AFM2 → AFM2 → AFM2 → AFM1 → AFM1 → AFM1 → FM) under an applied potential of −0.20 V/RHE. In neutral solvent, the magnetic transitions occur according to this pathway (FM → AFM2 → AFM2 → FM → AFM1 → AFM1 → AFM1 → FM) under an applied potential of −0.14 V/RHE. In an alkaline solvent, the magnetic transitions proceed along this sequence (FM → AFM1 → AFM2 → FM → AFM1 → AFM1 → AFM1 → FM) under an ultralow potential of −0.08 V/RHE. Essentially, the improvement of catalytic property is attributed to the synergistic influence of external potential and magnetic-state transition on the adsorption of reaction species (e.g., NO and NH3). Magnetic transitions are closely associated with ligand field effect of metal site with variable valence electron induced by applied potential. In general, this study provides valuable insights for the controllable design of magnetic metal catalysts.

Topological Defects Induced High-Spin Quartet State in Truxene-Based Molecular Graphenoids

Topological Defects Induced High-Spin Quartet State in Truxene-Based Molecular Graphenoids

Rogue breather modes: Topological sectors, and the ‘belt-trick’, in a one-dimensional ferromagnetic spin chain

We present explicit solutions for breather soliton modes of excitation in the one-dimensional Heisenberg ferromagnetic spin chain. We identify a characteristic geometrical feature of these breather modes wherein a helicoidal configuration of spins is continuously transformed to one which differs from the initial helicoid by a total twist of `2'. This is a curious manoeuvre popularly known as the `belt trick', an illustration of the simple connectedness of the $\rm{SU}(2)$ group manifold, and its rotation period $4\pi$. We show that this effectively splits the configuration space of the ferromagnetic chain in one-dimension into two topological sectors, distinguished by their total twist -- either `0', or `1'. Further, the energy lower bound of the two sectors is separated by a finite gap varying inversely with the size of the lattice.

High-pressure dc magnetic measurements on a bisdiselenazolyl radical ferromagnet using a vibrating-coil SQUID magnetometer

By using a vibrating-coil SQUID magnetometer, a ferromagnetic state with ${T}_{C}$ at the 30 K level is confirmed for the organic ferromagnet IBPSSEt. The high-pressure dc susceptibility has been measured in order to explore the pressure dependence on the dimensionality of the magnetic interaction network in IBPSSEt, which displays an ideal three-dimensional ferromagnetic network at 2 GPa with ${T}_{C}$ = 27.5 K. At more elevated pressures, the structure is best described in terms of a one-dimensional ferromagnetic chain.

Ferromagnetic Exchange in Bichloride Bridged Cu(II) Chains: Magnetostructural Correlations between Ordered and Disordered Systems

The synthesis, structure, magnetic properties, and theoretical analysis of a new phase of dichloro(2-chloro-3-methylpyridine)copper(II) (2) and its isomorphous analogue dichloro(2-bromo-3-methylpyridine)copper(II) (3) are reported. Both complexes crystallize in the orthorhombic space group Pbca and present square pyramidal Cu(II) ions bridged into chains by chloride ions with each copper(II) bearing a single pyridine ligand. Variable temperature magnetic susceptibility measurements were well fit by a uniform one-dimensional ferromagnetic chain model with 2, J = 69.0(7) K, C = 0.487 emu-K/mol-Oe; 3, J = 73.9(4) K, C = 0.463 emu-K/mol-Oe (H = -JΣSi·Sj Hamiltonian). The experimental J-values were confirmed via theoretical calculations. Comparison to a known disordered polymorph of dichloro(2-chloro-3-methylpyridine)copper(II), 1, shows marked differences as there are significant antiferromagnetic next-nearest neighbor interactions in 1 in addition to randomness induced by the disorder which provide a distinctly different magnetic response. The differences in magnetic behavior are attributed principally to the structural difference in the Cu(II) coordination sphere, 1 being significantly closer to trigonal-bipyramidal, whose difference changes both the nearest and next-nearest neighbor interactions.

Quantum breathers in XXZ ferromagnetic chains with on-site easy-plane anisotropy

The existence and properties of quantum breathers in a one-dimensional XXZ ferromagnetic Heisenberg spin chain with single-ion easy-plane anisotropy are investigated analytically in the Hartree approximation. We show that the system can support the appearance of quantum breathers, and discuss their existence conditions and properties. In addition, our results show that, for quantum breathers in this system, both the corresponding energy and magnetic moment are quantized.

Quantum Breathers in Anisotropy Ferromagnetic Chains with Second-Order Coupling

Under considering the next-nearest-neighbor interaction, quantum breathers in one-dimensional anisotropy ferromagnetic chains are theortically studied. By introducing the Dyson-Maleev transformation for spin operators, a map to a Heisenberg ferromagnetic spin lattice into an extended Bose–Hubbard model can be established. In the case of a small number of bosons, by means of the numerical diagonalization technique, the energy spectrum of the corresponding extended Bose–Hubbard model containing two bosons is calculated. When the strength of the single-ion anisotropy is enough large, a isolated single band appears. This isolated single band corresponds to two-boson bound state, which is the simplest quantum breather state. It is shown that the introduction of the next-nearest-neighbor interaction will lead to interesting band structures. In the case of a large number of bosons, by applying the time-dependent Hartree approximation, quantum breather states for the system is constructed. In this case, the effect of the next-nearest-neighbor interaction on quantum breathers is also analyzed.

Quantum breathers in Heisenberg ferromagnetic chains with Dzyaloshinsky-Moriya interaction.

We present an analytical study on quantum breathers in one-dimensional ferromagnetic XXZ chains with Dzyaloshinsky-Moriya interaction by means of the time-dependent Hartree approximation and the semidiscrete multiple-scale method. The stationary localized single-boson wave functions are obtained and these analytical solutions are checked by numerical simulations. With such stationary localized single-boson wave functions, we construct quantum breather states. Furthermore, the role of the Dzyaloshinsky-Moriya interaction is discussed.

Hierarchy of bound states in the one-dimensional ferromagnetic Ising chain CoNb2O6 investigated by high-resolution time-domain terahertz spectroscopy.

Kink bound states in the one-dimensional ferromagnetic Ising chain compound CoNb2O6 have been studied using high-resolution time-domain terahertz spectroscopy in zero applied magnetic field. When magnetic order develops at low temperature, nine bound states of kinks become visible. Their energies can be modeled exceedingly well by the Airy function solutions to a 1D Schrödinger equation with a linear confining potential. This sequence of bound states terminates at a threshold energy near 2 times the energy of the lowest bound state. Above this energy scale we observe a broad feature consistent with the onset of the two particle continuum. At energies just below this threshold we observe a prominent excitation that we interpret as a novel bound state of bound states--two pairs of kinks on neighboring chains.

Quantum breathers in ferromagnetic chains with on-site easy axis anisotropy

Quantum breathers in one-dimensional ferromagnetic chains with on-site easy axis anisotropy are investigated analytically. Based on the Hartree approximation, we can work out the case of quantum breathers with a large number of quanta. By using the multiple-scale method combined with the semidiscrete approximation, the nonlinear Schrödinger equation is derived. It is shown that quantum breathers can exist in the Heisenberg ferromagnetic chain. In addition, we obtain the energy level formula of quantum breathers, which indicates that the energy of such quantum breathers is quantized.

Quantum Solitons and Breathers in an Anisotropic Ferromagnet with Octupole-Dipole Interaction

By using a full quantum approach based on the time-dependent Hartree approximation and the semidiscrete multiple-scale method, we study quantum nonlinear excitations in a one-dimensional ferromagnetic chain with octupole-dipole interaction and on-site uniaxial anisotropy. We find that quantum solitons and breathers can exist in the ferromagnetic chain, and analyze existence conditions of these excitations. Since the system states corresponding to quantum breathers are stationary states, we can get the energy level formula of such quantum breathers.

INTERACTIONS BETWEEN THE TIME-VARYING ELECTROMAGNETIC FIELD AND THE QUANTUM SOLITARY WAVE IN A FERROMAGNETIC CHAIN

Starting with the Heisenberg Hamiltonian of the one-dimensional ferromagnetic chain in external fields, we have studied quantum characteristics of solitary waves and interactions between solitary waves and the time-varying electromagnetic field. It is shown that the energy and magnetic moments of the solitary wave are quantized. Utilizing these novel results, we have obtained the Bloch's equation of the two-level quantum solitary wave in a simple harmonic magnetic field.

Solitary excitations in one-dimensional ferromagnetic spin chains with biquadratic exchange interaction

By using the traveling wave method, the solutions of the elliptic function wave and the solitary wave are obtained in a ferromagnetic spin chain with a biquadratic exchange interaction, a single ion anisotropic interaction and an anisotropic nearest neighbour interaction. The effects of the biquadratic exchange interaction and the single ion anisotropic interaction on the properties (width, peak and stability) of the soliton are investigated. It is also found that the effects vary with the strengths of these interactions.

Iron(II) complexes containing thiophene-substituted “bispicen” ligands — Spin-crossover, ligand rearrangements, and ferromagnetic interactions

The synthesis and characterization of three new tetradentate “bispicen-type” ligands containing a substituted thiophene heterocycle are described [2,5-thienyl substituents = H (7), Ph (8), or 2-thienyl (9)]. Iron(II) bis(thiocyanate) coordination complexes containing 7–9 were prepared, and the electronic and variable-temperature magnetic properties of complexes containing 7 (10) and 9 (12) are described. Complex 10 features a gradual and incomplete spin crossover in the solid state, and 12 remains high-spin over the entire temperature range. Complex 11 is extremely unstable and rearranges to another iron(II) complex (13), which was structurally characterized. The temperature-dependent magnetic properties of 13 are described as a one-dimensional ferromagnetic chain, with interchain antiferromagnetic interactions and (or) zero-field splitting dominant at low temperatures. The magnetic analysis is corroborated by the molecular packing and density functional theory calculations, which suggest intermolecular interactions between coordinated thiocyanate ligands bearing a significant spin density.

Energy levels and magnetic moments of the quantum solitary wave in a one-dimensional ferromagnetic chain

By using the Hartree approximation and the simplified method of quasidiscreteness multiple scales, we have studied quantum solitary wave solutions for a one-dimensional ferromagnetic chain with exchange interaction and classical magnetic moment interaction. In this chain there are both traveling and stationary quantum solilary waves. With the help of the obtained quantum solitary wave solution, the energy levels and magnetic moments of the quantum solitary wave have been investigated further. It is shown that the energy and magnetic moments of the quantum solitary wave are quantized. These novel results provide a possible way for understanding macroscopic quantum effects such as quantum steps of the hysteresis loop in magnetic materials.

AM-6: a microporous one-dimensional ferromagnet

The vanadosilicate zeolite AM-6 is shown by a combination of spectroscopic techniques (UV-vis, Raman, XPS, XAS and EPR) to contain linear chains of alternating V=O and V-O bonds. The V(IV) ions in these chains are ferromagnetically coupled, and an excellent fit a to the susceptibility data with a one-dimensional Heisenberg model is obtained with J = 0.66(1) cm(-1). AM-6 is thus the first reported example of a microporous material incorporating one-dimensional ferromagnetic chains.

Quantum Solitary Wave Solutions in a Ferromagnetic Chain with Nearest- and Next-Nearest-Neighbor Interaction

The quantum solitary wave solutions in a one-dimensional ferromagnetic chain is investigated by using the Hartree–Fock approach and the multiple-scale method. It is shown that quantum solitary wave solutions can exist in a ferromagnetic system with nearest- and next-nearest-neighbor exchange interaction, and at the certain value of the first Brillouin zone, the solitary wave solution of the Hartree wave function becomes the intrinsic localized mode.

Chirality tunneling and quantum dynamics for domain walls in mesoscopic ferromagnets

We studied the quantum dynamics of ferromagnetic domain walls (topological kink-type solitons) in one-dimensional ferromagnetic spin chains. We show that the tunneling probability does not depend on the number of spins in a domain wall; thus, this probability can be large even for a domain wall containing a large number of spins. We also predict that there is a strong interplay between the tunneling of a wall from one lattice site to another (tunneling of the kink coordinate) and the tunneling of the kink topological charge (so-called chirality). Both of these elementary processes are suppressed for kinks in one-dimensional ferromagnets with half-integer spin. The dispersion law (i.e., the domain wall energy versus momentum) is essentially different for chains with either integer or half-integer spins. The predicted quantum effects could be observed for mesoscopic magnetic structures, e.g., chains of magnetic clusters, large-spin molecules, or nanosize magnetic dots.

Structural and magnetic properties of(Fe0.93Ni0.07)2P

Structural and magnetic properties of(Fe0.93Ni0.07)2P havebeen investigated by means of powder x-ray and neutron diffraction, magnetization and paramagneticsusceptibility measurements over a temperature range of 10–500 K. The system crystallizes in theFe2P type hexagonal structure ( space group, Z = 3) in which the Ni atoms occupy the tetrahedralMI sites with total preference. Refined values of the cell parametersand bond distances are found slightly higher than those forFe2P and the atomic positional parameters are found quite close to those reported for the parent compoundFe2P. The temperature dependence of the magnetization shows a sharp magnetic phasetransition around 298(5) K. However there is difference of the zero-field cooled andfield cooled modes of the magnetization, which is indicative of the formation offerromagnetic clusters. The ferromagnetic to paramagnetic transition shifts towardsthe higher temperature side with increase in the applied magnetic field, whichindicates that the phase transition is a field induced type first-order magneticphase transition. There is no crystallographic structural transition associated withthe magnetic phase transition. The transition is caused by the change in thec/a ratio. The alloy retains the ferromagnetic order ofFe2P with the moments orienting along the [001] direction. The Rhodes–Wohlfarth ratio(µp/µs) of(Fe0.93Ni0.07)2P is foundto be 1.53 (>1), showing itinerant magnetism in this compound. At 297 K the magnetic moment at theMI site is found negligiblebut at the MII site itis ∼0.51 µB. The observednon-linearity above Tc in the χ−1–T curve gives clear evidence of the presence of short range magnetic order aboveTc. The momentsat the MII sites in the paramagnetic state and the exchange interactions are responsible forthe short range one-dimensional ferromagnetic chains along [001] well above theTc in(Fe0.93Ni0.07)2P.

Solitons in a one-dimensional ferromagnetic chain under the influence of single-ion anisotropy

Cnoidal wave solutions and soliton solutions in a one-dimensional ferromagnetic chain with anisotropy exchange interaction and single-ion anisotropy are obtained through travelling wave solution method and the influence of single-ion anisotropy on cnoidal waves and solitons is discussed. The results indicate that single-ion anisotropy makes the cnoidal waves and solitons easy to excite in an easy-plane ferromagnetic chain but difficult in an easy-axis one, and makes them more stable in the easy-axis ferromagnetic chain but less stable in the easy-plane one. The influence of single-ion anisotropy on soliton excitations in a one-dimensional isotropic ferromagnet is also discussed.