Ground-state Magnetization Curve Research Articles

Exact studies of the ground-state properties of the anisotropic Heisenberg dimer with spin [formula omitted

The extended Heisenberg Hamiltonian for the atomic dimer with spin S=1 is diagonalized exactly. The anisotropy of the exchange interaction, single-ion anisotropy and the biquadratic exchange interaction are taken into account. It has been assumed that the external magnetic field can be heterogeneous and different on both atoms of the dimer. Based on the rigorous analytical solutions, the ground state properties of the dimer are studied numerically in a wide range of Hamiltonian parameters. In particular, the energy spectrum, biquadratic moment, residual entropy, ground-state phase diagrams and magnetization curves are calculated. The results are presented in the figures and discussed.

Effect of uniaxial single-ion anisotropy on a stability of intermediate magnetization plateaus of a spin-1 Heisenberg diamond cluster

Ground-state phase diagrams and magnetization curves of a spin-1 Heisenberg diamond cluster with two different coupling constants and uniaxial single-ion anisotropy are investigated in a presence of the external magnetic field with the help of exact diagonalization methods. It is shown that the spin-1 Heisenberg diamond cluster exhibits several remarkable quantum ground states, which are manifested in zero- and low-temperature magnetization curves as intermediate plateaus at one-quarter, one-half and three-quarters of the saturation magnetization. It is found that the width of the fractional magnetization plateaus depends basically on a relative strength of the coupling constants as well as uniaxial single-ion anisotropy, which may substantially shrink or even cause full breakdown of some intermediate magnetization plateaus. It is evidenced that a relatively weak uniaxial single-ion anisotropy of the easy-axis type considerably improves a theoretical fit of low-temperature magnetization curves of the tetranuclear nickel complex [Ni4 (μ-CO3)2(aetpy)8](ClO4)4 in a low-field region without spoiling the previous fit based on the fully isotropic Heisenberg model in a high-field region.

Heterobimetallic Dy-Cu coordination compound as a classical-quantum ferrimagnetic chain of regularly alternating Ising and Heisenberg spins

A classical-quantum chain composed of regularly alternating Ising and Heisenberg spins is rigorously solved by considering two distinct local anisotropy axes of the Ising spins. The ground-state phase diagram and magnetization curves are examined depending on a spatial orientation of the applied magnetic field. The phase diagram totally consists of four distinct phases and a few macroscopically degenerate points, where an outstanding coexistence of perfect order and complete disorder occurs within the so-called ‘half-fire, half-ice’ state. The zero-temperature magnetization curves generally exhibit a smooth dependence on a magnetic field owing to a canting angle between two coplanar anisotropy axes of the Ising spins, which enforces a misalignment of the magnetization vector from a direction of the applied magnetic field. It is evidenced that the investigated spin-chain model reproduces magnetic features of the heterobimetallic coordination compound Dy(NO)3(DMSO)2Cu(opba)(DMSO)2 (DMSO = dimethylsulfoxide, opba = orthophenylenebisoxamato). The high-field magnetization data reported for the powder sample of this polymeric coordination compound generally display a substantial smoothing on account of a powder averaging.

29p-YH-13 ボンド交代のある最近接相互作用と一様な次近接相互作用をもつ S=1/2鎖の基底状態磁化曲線

29p-YH-13 ボンド交代のある最近接相互作用と一様な次近接相互作用をもつ S=1/2鎖の基底状態磁化曲線

The Magnetization Process of the Spin-One Triangular-Lattice Heisenberg Antiferromagnet

We apply the coupled cluster method and exact diagonalzation to study the uniform susceptibility and the ground-state magnetization curve of the triangular-lattice spin-1 Heisenberg antiferromagnet. Comparing our theoretical data for the magnetization curve with recent measurements on the s=1 triangular lattice antiferromagnet Ba3NiSb2O9 we find a very good agreement.

Spin-1/2 XXZ Diamond Chain within the Jordan-Wigner Fermionization Approach

Park Angelinum 9, 040 01 Kosice, Slovak Republic Institut fur Theoretische Physik, Universitat Magdeburg, P.O. Box 4120, Germany The spin-1/2 XXZ diamond chain is considered within the Jordan–Wigner fermionization. The fermionized Hamiltonian contains the interacting terms which are treated within the Hartree–Fock approximation. We obtain the ground-state magnetization curve of the model for some particular cases and compare the results with the exact diagonalization data for finite chains of 30 spins and known exact results. We also analyze the validity of the suggested approximation.

Formation of quantum magnetization plateaux in mixed-spin Ising chains with single-ion anisotropy

We investigate the physical processes which give rise to a multi-plateau ground-state magnetization curve in ferrimagnetic Ising chains with alternating spins ( S, s) and different single-ion anisotropies on each sublattice of the system under an applied magnetic field, by using an elaboration of the molecular-field theory. Our analysis is started with the system ( S , 1 2 ) for which we use the transfer-matrix technique for comparison. In this system, we find a double-plateau structure (initial and saturation) in the magnetization curve for all values of S > 1 2 , independent of anisotropies. Then we study two more elaborate systems, comparing the results with density-matrix renormalization group calculations, and finally generalize our argument to the general case. We find that for a specified range of the anisotropy parameters, the system exhibits 2 s+1 plateaux, including the two classical and all those allowed for general quantum spin chains. This follows a similar rule as that known for spin- S ( S ≥ 1 ) Ising chains with single-ion anisotropy, for which 2 S+1 plateaux appear in the ground-state magnetization curve, surviving even at low temperatures.

Half magnetization plateau of a frustrated S = 1 antiferromagnetic chain

We numerically investigate the magnetization process of a frustrated S=1 chain with antiferromagnetic nearest-neighbor (nn) and next-nearest-neighbor (nnn) exchange interactions, which compete with each other, and also with uniaxial single-ion-type anisotropy energies. Special attention is paid to the half magnetization plateau which appears at the half of the saturation magnetization in the ground-state magnetization curve. We determine the parameter region where this plateau appears by employing the level spectroscopy method, and find that the plateau appears even in the absence of the single-ion-type anisotropy, if the ratio of the nnn to the nn interaction constant is in a specified region.

One-Third Magnetization Plateau in an Anisotropic (S,S')=(1,2) Spin-Alternating Chain

Employing numerical methods, we study the ground-state magnetization curve of a ( S , S ')=(1,2) spin-alternating chain with uniaxial single-ion anisotropies, where S =1 and S '=2 spins are alternating and coupled antiferromagnetically. Special attention is paid to the magnetization plateau, the one-third plateau, which appears at one third of the saturation magnetization in the ground-state magnetization curve. We find that three kinds of one-third plateaux appear, one of which has a quantum nature, while the remaining two have a classical (Ising) nature. We determine the one-third plateau phase diagram on the D 2 versus D 1 plane, where D 1 ( D 2 ) is the ratio of the single-ion anisotropy constant for the S =1 ( S '=2) spin to the exchange interaction constant. This phase diagram consists of a phase boundary line between the quantum and classical one-third plateau states as well as three phase boundary lines between the one-third plateau and plateauless states. We emphasize that there is no phase trans...

Finite-field ground state of an [formula omitted] zigzag ladder

Using numerical methods, we study the finite-field ground state of an S = 1 zigzag ladder. Special attention is paid to the magnetization plateau which appears at a half of the saturation magnetization in the ground-state magnetization curve.

1/3 magnetization plateau in a one-dimensional anisotropic ferrimagnet

Using mainly numerical methods, we investigate the ground-state magnetization curve of a mixed spin chain with uniaxial single-ion anisotropies, where S = 1 and S = 2 spins are alternating and coupled antiferromagnetically. Special attention is paid to the magnetization plateau, the 1/3-plateau, which appears at one third of the saturation magnetization in the magnetization curve. It is found that there appear three kinds of 1/3-plateaux, one of which has a quantum nature, while the remaining two have a classical (Ising) nature.

Finite-Field Ground State of anS= 1 Anisotropic Antiferromagnetic Chain

We investigate, using numerical methods, the finite-field ground-state properties of an S=1 anisotropic antiferromagnetic chain described by the Hamiltonian H = Σ {S x S x +1 + S y S f +1 + ΔS z Sz +1 } + DΣ(S z ) 2 - H Σ S 2 . It is found that the magnetization jump anomaly (a first-order phase transition) appears in the ground-state magnetization curve when Δ=5.0 and -1.50D 1.05; in a certain region of D, the jump starts from a finite value of the magnetization m per spin. We also find that the a second-order phase transition between commensurate and incommensurate gapless phases takes place in the finite-field ground state. The critical point of this transition as well as the values of m at the onset and end of the magnetization jump is summarized in the m versus D phase diagram.

Half Plateau Phase Diagram in Generalized Zig-Zag Spin Ladder

We study the finite-field ground state of an anisotropic S = 1/2 antiferromagnetic chain with bond-alternating nearest-neighbor and uniform next-nearest-neighbor interactions. The ground-state magnetization curve of this model has a plateau at a half of the saturation magnetization in a certain parameter region. We analytically investigate the plateau phase of this model by use of tlie degenerate perturbation theory up to the second order.

Finite-Field Ground State of theS=1 Antiferromagnetic–Ferromagnetic Bond-Alternating Chain

We investigate the finite-field ground state of the S=1 antiferromagnetic-ferromagnetic bond-alternating chain described by the Hamiltonian ${\calH}=\sum\nolimits_{\ell}\bigl\{\vecS_{2\ell-1}\cdot\vecS_{2\ell} +J\vecS_{2\ell}\cdot\vecS_{2\ell+1}\bigr\} +D\sum\nolimits_{\ell} \bigl(S_{\ell}^z)^2 -H\textstyle\sum\nolimits_\ell S_\ell^z$, where \hbox{$J\leq0$} and \hbox{$-\infty<D<\infty$}. We find that two kinds of magnetization plateaux at a half of the saturation magnetization, the 1/2-plateaux, appear in the ground-state magnetization curve; one of them is of the Haldane type and the other is of the large-$D$-type. We determine the 1/2-plateau phase diagram on the $D$ versus $J$ plane, applying the twisted-boundary-condition level spectroscopy methods developed by Kitazawa and Nomura. We also calculate the ground-state magnetization curves and the magnetization phase diagrams by means of the density-matrix renormalization-group method.

Magnetization plateaux in an anisotropic [formula omitted] antiferromagnetic chain with frustration and bond-alternation

Using numerical methods, we study the finite-field ground state of an anisotropic S= 1 2 antiferromagnetic chain with bond-alternating nearest-neighbor and uniform next-nearest-neighbor interactions. Special attention is paid to the magnetization plateaux at a half and one-third of the saturation magnetization, which appear in the ground-state magnetization curve.

Ground-state properties of an S=-chain with ferro- and antiferromagnetic interactions

Abstract Using numerical methods, we investigate the ground-state properties of an S= 1 2 Δ -chain in which the nearest-neighbor exchange interactions between apical and basal spins are ferromagnetic and those between basal spins are antiferromagnetic. We find that the ground state of the system is the ferromagnetic or the ferrimagnetic state depending on whether the former interaction constant is larger or smaller than the twice of the latter one. We also discuss the ground-state magnetization curve of the system in connection with experimental results for [Cu(bpy)H2O][Cu(bpy)(mal)H2O](ClO4)2.

Ground State and Magnetization Process of the Mixture of Bond-Alternating and UniformS=1/2 Antiferromagnetic Heisenberg Chains

The mixture of bond-alternating and uniform S=1/2 antiferromagnetic Heisenberg chains is investigated by the density matrix renormalization group method. The ground state magnetization curve is calculated and the exchange parameters are determined by fitting to the experimentally measured magnetization curve of \CuCl$_{2x}$Br$_{2(1-x)}$($\gamma$-pic)$_2$. The low field behavior of the magnetization curve and low temperature behavior of the magnetic susceptibility are found to be sensitive to whether the bond-alternation pattern (parity) is fixed all over the sample or randomly distributed. The both quantities are compatible with the numerical results for the random parity model.

Multiplateau magnetization curves of one-dimensional Heisenberg ferrimagnets

Ground-state magnetization curves of ferrimagnetic Heisenberg chains of alternating spins $S$ and $s$ are numerically investigated. Calculating several cases of $(S,s)$, we conclude that the spin-$(S,s)$ chain generally exhibits $2s$ magnetization plateaux even at the most symmetric point. In the double- or more-plateau structure, the initial plateau is generated on a classical basis, whereas the higher ones are based on a quantum mechanism.

Metamagnetism in theXXZmodel with next-to-nearest-neighbor coupling

We investigate groundstate energies and magnetization curves in the one dimensional XXZ-model with next to nearest neighbour coupling $\alpha>0$ and anisotropy $\Delta$ ($-1 \le \Delta \le 1$) at T=0. In between the familiar ferro- and antiferromagnetic phase we find a transition region -- called metamagnetic phase -- where the magnetization curve is discontinuous at a critical field $B_c(\alpha,\Delta)$.

Ground-state magnetization curve of a generalized spin-1/2 ladder

Employing a method of exact diagonalization for finite-size systems, we investigate the magnetization curve in the ground state of an antiferromagnetic spin- 1 2 ladder with additional exchange interactions on diagonal bonds, which is equivalent to an antiferromagnetic spin- 1 2 chain with bond-alternating nearest-neighbor and uniform next-nearest-neighbor interactions. It is found that a half-plateau appears in the magnetization curve in a certain range of the interaction constants. This result is discussed in connection with the necessary condition for the appearance of the plateau, recently given by Oshikawa et al.