Magnetic quantum phase transitions and entropy in Van Vleck magnet

Lavanov, G. Yu.; Каліта, В. М.; Ivanova, I.; Локтев, В. М.

doi:10.1016/j.jmmm.2016.05.017

Cited by 5 publications

(4 citation statements)

References 31 publications

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“…It is a transition between two AFM phases with different lattice magnetization values. At = 0, it is a magnetic quantum PT [33][34][35][36][37][38], at which the ground state of ions in sublattice 2 becomes a singlet one, |−1⟩ → |0⟩, and the singleion anisotropy energy becomes lower. At ̸ = 0, the minimization of the single-ion anisotropy energy at the isostructural PT is associated with a jump-like change in the ionic states: the population is maximum for ions in sublattice 2 with a spin projection of −1 before the transition point and with the zero spin projection after it.…”

Section: Discussionmentioning

confidence: 99%

“…When determining the states, PT points, and phase stability boundaries, we can use the Lagrange function written as a functional of the parameters [33,34]. It looks like = 1 2…”

Section: Model Hamiltonianmentioning

confidence: 99%

“…At = 0, the states are determined by minimizing the Lagrange function with respect to the wave function parameters, ( ) [33,34]. In so doing, it is easy to verify that the following states can be stable:…”

Section: Model Hamiltonianmentioning

confidence: 99%

“…The equilibrium states and the boundaries of their stability can be found by minimizing the free energy ( , ) [33]. In the general case, the problem of finding the sequence of PTs is nonlinear and has to be solved numerically.…”

Section: Free Energy Of the Systemmentioning

confidence: 99%

See 3 more Smart Citations

Magnetization and Magnetocaloric Effect in Antiferromagnets with Competing Ising Exchange and Single-Ion Anisotropies

2020

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The magnetization of a two-sublattice Ising antiferromagnet with easy-plane single-ion anisotropy, which is accompanied by two phase transitions, has been studied. The both phase transitions are induced by the magnetic field. One of them is isostructural, i.e., the system symmetry remains unchanged and a transition between two antiferromagnetic states with different sublattice magnetizations takes place. The other phase transition occurs when the antiferromagnetic state transforms into the ferromagnetic one. At both phase transitions, the field dependence of the system entropy has two successive positive jumps, which is not typical of ordinary antiferromagnets. On the other hand, if the temperature of the system is higher than the tricritical temperature of the isostructural phase transition, there appears a continuous maximum in the field dependence of the entropy.

show abstract

Section: Discussionmentioning

confidence: 99%

“…When determining the states, PT points, and phase stability boundaries, we can use the Lagrange function written as a functional of the parameters [33,34]. It looks like = 1 2…”

Section: Model Hamiltonianmentioning

confidence: 99%

Section: Model Hamiltonianmentioning

confidence: 99%

Section: Free Energy Of the Systemmentioning

confidence: 99%

See 2 more Smart Citations

Magnetization and Magnetocaloric Effect in Antiferromagnets with Competing Ising Exchange and Single-Ion Anisotropies

2020

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Effect of the exchange interaction anisotropy on the magnetic quantum phase transitions in dimerized antiferromagnets

Lyashenko

Каліта

Локтев

2017

Low Temperature Physics

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We present a theoretical description of a quantum phase transition in a dimerized antiferromagnet, induced by an external magnetic field. The description of such transitions is constructed by determining the minimum of the Lagrange function which depends on the parameters of the ground-state crystal wavefunction. We determine that during a crystal transition from the singlet state of the dimer to the state with a noncollinear spin orientation, an order-order type phase transition occurs. We show that in the case of a single-axis character of the exchange anisotropy, the location of the quantum phase transition critical point is affected by the spin-spin interactions inside the dimer. Additionally, analogous to the classical Néele antiferromagnets, single-axis type anisotropic spin-spin interactions between dimers, shift the point of the spin-flip transition from the noncollinear antiferromagnetic phase to the ferromagnetic phase.

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Change in the entropy during a first-order phase transition induced by a magnetic field in an isotropic non-Heisenberg ferromagnet

Lavanov

Каліта

Локтев

2018

Low Temperature Physics

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We describe a first-order phase transition in an isotropic non-Heisenberg ferromagnet induced by a magnetic field with a fourth-order spin exchange interaction at temperatures above the Curie point. The field behavior of the magnetization is analyzed and the temperature dependences of the critical fields of the stability of the paramagnetic and ferromagnetic phases as well as the critical field of the phase transition between them are determined. It is shown that this first-order phase transition has a finite amplitude of the magnetization jump and can occur in small magnetic fields. An H-T phase diagram is presented. It is found that the amplitude of the phase jump during the magnetic field-induced transition from the paramagnetic to the ferromagnetic phase can exceed the magnitude of the entropy change of an isotropic Heisenberg ferromagnet by two orders of magnitude when it is magnetized at the Curie point. It is shown that the expansion of the free energy model up to the 6th power in magnetization can only qualitatively describe the entropy behavior in the phase transition between the paramagnetic and ferromagnetic phases. Published by AIP Publishing.

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Magnetic quantum phase transitions and entropy in Van Vleck magnet

Cited by 5 publications

References 31 publications

Magnetization and Magnetocaloric Effect in Antiferromagnets with Competing Ising Exchange and Single-Ion Anisotropies

Magnetization and Magnetocaloric Effect in Antiferromagnets with Competing Ising Exchange and Single-Ion Anisotropies

Effect of the exchange interaction anisotropy on the magnetic quantum phase transitions in dimerized antiferromagnets

Change in the entropy during a first-order phase transition induced by a magnetic field in an isotropic non-Heisenberg ferromagnet

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