Nonlinear nano-scale localized breather modes in a discrete weak ferromagnetic spin lattice

Kavitha, L.; Parasuraman, E.; Gopi, D.; Prabhu, A.; Vicencio, Rodrigo A.

doi:10.1016/j.jmmm.2015.10.021

Cited by 64 publications

(17 citation statements)

References 72 publications

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“…Теоретический поиск ДБ в спиновых системах был проведен в работах [8 -14], где была продемонстрирована возможность их возникновения в гейзенберговских цепочках с одноионной магнитной анизотропией. Отметим, что имеется определённый пробел в этой области, связанный с учётом более сложных спиновых взаимодействий, в частности, антисимметричного обмена [15], стремящегося стабилизировать гелимагнитное упорядочение магнитных моментов. В данной работе с применением численных методов показано существование нелинейных локализованных возбуждений в модели спиновой цепочки с взаимодействием Дзялошинского-Мория (ДМ) и отмечается связь этого взаимодействия с пространственной симметрией возбуждаемых бризерных мод на цепочках конечной длины.…”

Section: Introductionunclassified

Numerical simulation of magnetic discrete breathers in a Heisenberg spin chain with antisymmetric exchange

et al. 2021

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By using numerical methods, we consider possibility of the spatially localized breather-type excitations for the model of the discrete Heisenberg spin chain, which includes the antisymmetric exchange interaction, the single-ion anisotropy of the easy plane type, and the Zeeman interaction with an external magnetic field, which exceeds a critical field of the transition to the state of forced ferromagnetism. To find solutions, we used equations of motion for spin operators. The case is considered when the frequency of discrete magnetic breathers lies above the upper edge of the spin wave spectrum. The chain length used in the calculations had been taken as 100 and 101 nodes, and the open boundary conditions were used. To carry out numerical calculations, an original program was written which simplifies maximally calculation of spin deviations inside the chain and enables us to use parallel computing technologies. A classification of symmetric and antisymmetric solutions was established, which made it possible to halve a number of calculations for spin deviations. An algorithm was elaborated to specify the amplitudes of spin deviations, that makes possible to construct a desired breather solution in a reasonable amount of time. The numerical calculations of the spin spatial distribution show that it has an antisymmetric ordering with respect to the center of the chain in the presence of the Dzyaloshinskii-Moriya interaction. The center of the solution can be located either between the lattice nodes (Page mode) in the case of an even number of lattice sites, or directly at the node in the case of the odd number (Takeno-Sievers mode). In the first case, the breather mode contains an odd number of pairs of magnetic kinkantikinks with a maximum of the envelope function at the center. Breather modes include an even number of these pairs for an odd number of lattice nodes.

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Section: Introductionunclassified

Numerical simulation of magnetic discrete breathers in a Heisenberg spin chain with antisymmetric exchange

et al. 2021

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“…Currently, considerable numerical and theoretical progress has been achieved in understanding the nature of DB in Heisenberg spin chains with additional interactions, for instance, onsite anisotropy or next-nearest-neighbor exchange interactions [20][21][22][23][24][25][26] . Recently, formation of discrete breathers has been analyzed for weak ferromagnetic chains where the presence of the Dzyaloshinskii-Moriya (DM) interaction leads to a small canting between the interacting moments 27,28 . The DB solutions have been examined in dynamics of the 1D array of magnetic particles (dots) with the easy-plane anisotropy and interparticle magnetic dipole interaction 29 .…”

Section: Introductionmentioning

confidence: 99%

Dark discrete breather modes in monoaxial chiral helimagnet with easy-plane anisotropy

Bostrem,

Ekomasov,

Kishine

et al. 2021

Preprint

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Nonlinearity and discreteness are two pivotal factors for an emergence of discrete breather excitations in various media. We argue that these requirements are met in the forced ferromagnetic phase of the monoaxial chiral helimagnet CrNb3S6 due to specific domain structure of the compound. The stationary, time-periodic breather modes appear as the discrete breather lattice solutions whose period mismatches with a system size. Thanks to easy-plane single-ion anisotropy intrinsic to CrNb3S6, these modes are of the dark type with frequencies lying within the linear spin-wave band, close to its bottom edge. They represent cnoidal states of magnetization, similar to the well-known soliton lattice ground state, with differing but limited number of embedded 2π-kinks. Linear stability of these dark breather modes is verified by means of the Floquet analysis. Their energy controlled by two parameters, namely the breather lattice period and amplitude, falls off linearly with a growth of the kink number. These results may pave a new path to design spintronic resonators on the base of chiral helimagnets.

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“…Here we choose an alternative approach related to modulational instability of particular delocalized modes. Such instabilities lead to energy localization in the form of long-living chaotic DBs and subsequent transition to thermal equilibrium [22,[94][95][96][97][98][99][100][101][102][103]. In the course of this transition of a nonlinear chain, the local temperature and the specific heat can be calculated.…”

Section: Introductionmentioning

confidence: 99%

Effect of discrete breathers on the specific heat of a nonlinear chain

Singh,

Morkina,

Korznikova

et al. 2019

Preprint

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Defect-free crystal lattices can accommodate spatially localized, high amplitude atomic vibrations called either discrete breathers (DBs) or intrinsic localized modes (ILMs). This has been explored by a number of molecular dynamics studies and, in few cases, by the first-principles calculations. A number of experimental measurements of crystal vibrational spectra was performed aiming to prove the existence of DBs in thermal equilibrium at elevated temperature. However, the interpretation of these experimental results is still debated. Direct high-resolution imaging of DBs in crystals is hardly possible due to their nanometer size and short lifetime. An alternative way to substantiate the existence of DBs is to evaluate their impact on the measurable macroscopic properties of crystals and validate such prediction. One of such properties is specific heat. In fact, the measurements of heat capacity was done for alpha-uranium by Manley and co-workers in conditions where the presence of DBs was expected. In the present study, employing a one-dimensional nonlinear lattice with an on-site potential, we analyze the effect of DBs on its specific heat. In the most transparent way, this can be done by monitoring the chain temperature in a non-equilibrium process, at the emergence of modulational instability, with total energy of the chain being conserved. For the onsite potential of hard-type (soft-type) anharmonicity, the instability of q = π mode (q = 0 mode) results in the appearance of long-living DBs that gradually dissipate their energy and eventually the system approaches thermal equilibrium with spatially uniform and temporally constant temperature. The variation of specific heat at constant volume is evaluated during this relaxation process. It is concluded that DBs affect specific heat of the nonlinear chain and for the case of hard-type (softtype) anharmonicity they reduce (increase) the specific heat.

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Nonlinear nano-scale localized breather modes in a discrete weak ferromagnetic spin lattice

Cited by 64 publications

References 72 publications

Numerical simulation of magnetic discrete breathers in a Heisenberg spin chain with antisymmetric exchange

Numerical simulation of magnetic discrete breathers in a Heisenberg spin chain with antisymmetric exchange

Dark discrete breather modes in monoaxial chiral helimagnet with easy-plane anisotropy

Effect of discrete breathers on the specific heat of a nonlinear chain

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