Micromagnetic modelling of stripe domains in thin films with a columnar microstructure

A micromagnetic model of thin films with columnar microstructure in the form of a matrix with reduced magnetic properties and embedded columns with high aspect ratio is presented. Such microstructure is typical for some films based on rare-earth and 3d transition metal alloys, in particular for La-Co films, that were chosen as an object for our modelling. Described structural features promote an effective perpendicular magnetic anisotropy that for thick enough films leads to formation of the stripe domain pattern. Our work addresses to the problem of finding equilibrium characteristics of stripe domains for the case of infinite columnar films. Herein it is shown how width of stripe domains, remanent magnetization and energies depend on number of replicas of periodic boundary conditions and the size of modelling volume. Equilibrium values of listed quantities can be found by extrapolating obtained dependencies. © 2021 Author(s).This work was supported by Russian Science Foundation, project No. 19-72-00141

Investigation of Magnetization Reversal in Nanostructured Films Based on the TbCo System

Проведено исследование процессов перемагничивания тонких пленок Ta/Tb29Co71/Ta с различными типами наноструктурированиия. Осаждение магнитного материала производилось на пористую поверхность подложек, барьерный оксидный слой и сплошную подложку. Для всех пленок показано наличие сильной перпендикулярной магнитной анизотропии. Проанализированы процессы перемагничивания и характер доменной структуры для пленок на разных подложках. Для пленок, осажденных на пористые подложки, наблюдалось более чем трехкратное увеличение коэрцитивной силы по сравнению со сплошной и осажденной на барьерный слой пленками, которое сопровождалось уменьшением среднего размера доменов в области коэрцитивной силы.The magnetization reversal of thin Ta/Tb29Co71/Ta films with various types of nano structuring was investigated. The deposition of the magnetic material was carried out on the porous surface of the substrates, the barrier oxide layer and the continuous substrate. The presence of strong perpendicular magnetic anisotropy was shown for all types. The magnetization reversal processes and the character of the domain structure for films on different substrates was analyzed. For films deposited on porous substrates, a more than triple increase in coercivity was observed as compared to a continuous film, which was accompanied by a decrease in the average domain size in the coercivity region

ANALYSIS OF DEMAGNETIZATION PROCESS AND MAGNETIC ANISOTROPY OF A FENI THIN FILM

Investigation of the magnetization reversal of a FeNi thin magnetic film is performed. Magnetic hysteresis loops and angular dependences of both coercivity and remanence are obtained by Kerr magnetometry. An analysis of the above dependences and the dispersion of an easy magnetization axis are described using micromagnetic calculations

MAGNETIZATION ANISOTROPY OF YCo3 AND YFe3 COMPOUNDS

Anisotropy of magnetization is the difference between the saturation magnetizations along the hard magnetization axis (HA) and the easy magnetization axis (EA). The magnetization curves of YFe3 and YCo3 single crystals, which have prominent magnetization anisotropy, were measured in the temperature ranges up to 560 and 330 K, respectively. The temperature dependences of the saturation magnetization along EA and HA, as well as the parameter p characterizing the magnetization anisotropy, are established and analyzed

MICROMAGNETIC MODELING OF TENSOMAGNETORESISTANCE EFFECT IN FILMS WITH UNIDIRECTIONAL ANISOTROPY

The work is devoted to a micromagnetic modeling of magnetoresistance under compressive stress in multi-layer films with unidirectional anisotropy.Работа выполнена при финансовой поддержке Минобрнауки России, проект RFMEFI57815X0125

FEATURES OF MAGNETIZATION REVERSAL OF HARD MAGNETIC ALLOYS AT LOW TEMPERATURE

Major hysteresis loops of nanocrystalline alloys based on the Pr2Fe14B phase at T = 2 K have been studied. Depending on the composition and structure of the samples, magnetization reversal can be carried out both by a stepwise and by a continuous change in magnetization.Работа выполнена в рамках гранта МК-1746.2020.2

The Magnetic Properties Modelling of the Ensemble of Exchange Coupled Single Domain Particles

В магистерской диссертации представлены результаты моделирования магнитных гистерезисных свойств ансамбля обменносвязанных частиц. Для выполнения компьютерного моделирования разработан пакет компьютерных программ в среде MATLAB, позволяющий моделировать и анализировать предельные и частные петли магнитного гистерезиса для однофазных и многофазных ансамблей с различными типами магнитной анизотропии, упорядочением фаз, а также при параметрической зависимости микроскопических констант от температуры. Все это реализовано в рамках модели однодоменных нанокристаллитов, имеющих однородную намагниченность, процесс изменения которой осуществляются за счет когерентного вращения. Разработан алгоритм параллельного расчета, позволяющий основные арифметические и логически операции выполнять на графических ускорителях. Полученные с его помощью численные результаты качественно соответствуют экспериментальным данным для системы Nd-Fe-B.The results of magnetic properties modelling of the ensemble of exchange coupled particles are represented in this master's thesis. The computer modelling is realized in the MATLAB programming environment and allows performing calculations and analysis of major and minor magnetic hysteresis loops of single-phase or multiphase ensembles with different types of magnetic anisotropy, phase arrangement and with the parametric dependency of microscopic constants on temperature. The latter is based on the model of single domain nanocrystallites. Each of them has a uniform magnetization and any changes of one are happened by coherent rotation. The algorithm of parallel calculations using a graphic processing unit is also shown in the work. The obtained numeric results qualitatively are in compliance with the Nd-Fe-B experimental data

INTERGRAIN EXCHANGE INTERACTION OF Pr-Fe-B SYSTEM COMPOSITE NANOCRYSTALLINE ALLOYS

Hard magnetic composite materials are promising for improving hysteresis properties of permanent magnets. The aim of the work is to test the applicability of existing models of magnetization reversal processes of hard magnetic composite alloys based on intermetallic Pr2Fe14B type compound.Работа выполнена в рамках гранта МК-1746.2020.2. Авторы выражают благодарность к.ф.-м.н., доц. Селезнёвой Н.В. за выполнение рентгеноструктурного анализа