Spontaneous Perpendicular Anisotropy in Ultra-thin Ferromagnetic Films

Henao-Londoño, J. C.; Arbeláez-Echeverri, O. D.; Agudelo-Giraldo, J.D.

doi:10.1007/s10948-017-4005-9

Cited by 5 publications

(6 citation statements)

References 10 publications

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“…the deformation in the surface and boundary anisotropies. The surface anisotropy equation is presented in (7), in which the effective surface value is given by K S_e f = ε S v i K 1 , where ε S = 0.2, a parameter adjusted according to the change of the perpendicular and in-plane thickness dependence required, which is less than 10 muc [4,8].…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, the loss of the coordination number in the surface atoms connected with a loss of thickness must exert a temperature dependence. Although there exist different works presenting the modelling and simulation of magnetic behavior with surface effects, most of them refer to monocrystalline systems that do not reflect the real system's performance [3][4][5] where is expected, i.e., in similar way to most fabrication methods, in which the grain diameters are similar to the thickness magnitude. An extensive analysis of magnetic nano-grain phenomena was realized in previous works with a more realistic modelling [6].…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Thickness on the Magnetic Properties of Nanocrystalline Thin Films: A Computational Approach

Agudelo-Giraldo

García

2021

Computation

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A study of the magnetic behaviour of polycrystalline thin films as a function of their thickness is presented in this work. The grain volume was kept approximately constant in the virtual samples. The model includes the exchange interaction, magneto-crystalline anisotropy, surface anisotropy, boundary grain anisotropy, dipolar interaction, and Zeeman effect. The thickness-dependence of the critical temperature, blocking temperature, and irreversibility temperature are presented. Surface anisotropy exerts a great influence at very low thicknesses, producing a monodomain regime. As the thickness increases, the dipolar interaction produces a coupling in-plane of single domains per grain which favours superparamagnetic states. At higher thicknesses, the effects of the in-plane anisotropy produced by dipolar interaction and surface anisotropy decrease dramatically. As a result, the superparamagnetic states present three-dimensional local anisotropies by the grain.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Influence of Thickness on the Magnetic Properties of Nanocrystalline Thin Films: A Computational Approach

Agudelo-Giraldo

García

2021

Computation

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“…Moreover, there is strong evidence of the complicated formation of domain patterns in the reorientation regime [16]. Our previous work [17] demonstrated that magnetic thin films show a critical thickness for a ratio between dipolar interaction and surface anisotropy. There, an enhancement of the shape anisotropy spontaneously is produced and becomes perpendicular to the surface at low temperatures.…”

Section: Introductionmentioning

confidence: 93%

Effect of the surface anisotropy on the magnetic behavior of ultra-thin films single-domain on the spin reorientation transition regime by monte carlo simulation

Agudelo-Giraldo,

Giraldo-Daza,

Moscoso Londoño

et al. 2023

Phys. Scr.

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In this work, Monte Carlo simulations allowed for studying the effect of the surface anisotropy on the Spin Reorientation Transition regime for single-domain ultra-thin films. The simulations included spin moments (1), exchange constant (10 meV), magnetocrystalline anisotropy (0.5 meV), and dipolar magnetic interaction (0.05 meV). We evaluated the surface anisotropy constant for K S = 0.5, 1, and 2 meV and thicknesses ranging from 3 to 11 cells. We determined the magnetothermal and hysteresis loop in- and out-plane at different angles to the plane. Analysis of Variance allows for modeling the coercivity as a function of the thickness and the applied field direction (in- and out-plane). Under these simulation conditions, the Spin Reorientation Transitions appear only at a thickness of 7 cells with K S =1 meV. The main contribution to magnetization rises out-plane at low thicknesses and in-plane at high values. However, the dominant magnetization contribution is in-plane for the thickness of 7 cells and low surface anisotropy. The magnetization is mainly oriented, out-plane for the high surface anisotropy case. However, hysteresis loops were observed independent of the applied magnetic field direction and thickness. Analysis of Variance results suggests that the thickness and the applied magnetic field direction allowed for tunning the coercivity (hard or soft magnetic materials). Sample simulated ignoring the magnetocrystalline and the surface anisotropies produce magnetic components in- and out-plane with slight differences as angle function. The combination of dipolar interactions and magnetocrystalline anisotropy showed two magnetic behaviors, a hard magnetic phase at low angles and a soft one at high angles in-plane direction. The inverse behavior results in the out-plane component. We observed the same behavior when surface anisotropy is considered. The differences are the transition angle of 50° in the first case and 30° in the second.

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“…Uniaxial axis is defined by the unitary vector associated to → v i and a parameter of proportionality ε S was fixed in 0.2 according to a previous work 26 , which is a measure of the strength of the anisotropy or the spin-orbit coupling.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Under a reduced set of parameters, previous studies based upon grains size evidenced a range in which correlation between grains is low and phenomena needs to be better studied 32 . Furthermore, based on previous experiences in the simulation area 7,26,32 , it has been concluded that if parameters are adjusted to experimental ranges, how it was done, an analysis of magnetic behaviour of nano-poly-crystalline films with ferromagnetic magnetic cubic cell can be obtained. That is due to the different magnetic contributions acts in ranges of energy well defined.…”

Section: Model Descriptionmentioning

confidence: 99%

Grain boundary anisotropy on nano-polycrystalline magnetic thin films

Agudelo-Giraldo

Restrepo

2020

Sci Rep

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Grain boundaries in polycrystalline thin films with crystallite sizes at nanoscale presents regions characterized by a high degree of local structural disorder. As a consequence, great values of the associated local anisotropies are expected. On this regard, a systematic investigation of the effect of the grain boundary anisotropy on the magnetic properties in such type of nanostructured systems is addressed. For developing this work, a standard Monte Carlo simulation in the framework of classical Heisenberg spins was carried out, with a Hamiltonian involving exchange couplings, dipolar interactions, Zeeman interaction and contributions of cubic magneto-crystalline anisotropy. A quantification of local structural disorder was considered. Results revealed that i) by keeping the same number of grains, different organizations give rise to different spontaneous magnetizations, ii) the critical exponent of the magnetization differs of pure models, which is attributed to the complexity of the lattice and consistent with a distribution of critical temperatures, iii) Boundary anisotropy varies with temperature and its strength are determinant factors for blocking temperatures, and iv) Boundary anisotropy inside in the hysteretic properties where coercive field variations are observed.

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Spontaneous Perpendicular Anisotropy in Ultra-thin Ferromagnetic Films

Cited by 5 publications

References 10 publications

The Influence of Thickness on the Magnetic Properties of Nanocrystalline Thin Films: A Computational Approach

The Influence of Thickness on the Magnetic Properties of Nanocrystalline Thin Films: A Computational Approach

Effect of the surface anisotropy on the magnetic behavior of ultra-thin films single-domain on the spin reorientation transition regime by monte carlo simulation

Grain boundary anisotropy on nano-polycrystalline magnetic thin films

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