Registration Number
0215U002543,
0115U001469
, R & D reports
Title
The study of continuous and granular magnetic nano-films and 2D structures that are urgent for spintronics tasks.
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Head
Ryabchenko Sergiy Mykhajlovych,
Registration Date
06-01-2016
Organization
Institute of physics NASU
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The hysteresis and the critical phenomena of magnetic reversal of the superferromagnetic (SFM) state of the nano-granular film with perpendicular anisotropy, Co/Al2O3 with 57.2 ат. % Co, are investigated. For the films, which were grown up in one series with this one, the percolation threshold has been determined earlier through the dependence of the film electrical resistance from the contents of the Co granules as 61 ат %. It has been established earlier by the transmission electron microscopy of the nano-granular films of Co/Al2O3, that for the films of this growing series the perpendicular growth induced anisotropy is characteristic. It was established by the studying of magnetic atomic force microscopy, that this film already at room temperature is in SFM state with superdomains. Thus, the studying of influence of the SFM state on the characteristics of ensemble of one-domain particles was a task of investigation. It has been shown at research of a film that at its magnetization the transition from multidomain SFM conditions to homogeneous one occurs critically. The value of a critical field of transition to homogeneous SFM state depends from the demagnetizing fields, anisotropies of granules and anisotropies of the interparticles exchange interaction. It is obtained, that, despite of SFM state of the studied film, the coercive force has temperature dependence, which not strongly differs from Neel-Brown's formula for the noninteracting anisotropic one-domain ferromagnetic particles while angular dependence of the coercive fields turned out anomalous. It has been shown, that these features of the coercive fields are a consequence of magnetic reversal of a film by the movement of a domain walls, which is realized due to tumbling of the magnetic moments of particles in area of borders between superdomains, which are extremely narrow. The last circumstance leads to compensation of the contribution of an exchange field in the coercivity. Thus, the main factors, which influence on the coercivity, are anisotropy of particles, which blocks reorientation of their magnetic moments, and the factor of demagnetizing of a film. Results can be used at creation of functional elements on a basis of nano-granular films, in the further scientific researches and in educational process for interpretation of concept "superferromagnetism" of nano-structures and a common and difference sides of this phenomenon with the ferromagnetism of the bulk materials.
Product Description
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Бондар Олександр Васильович
Калита Віктор Михайлович
Кулик Микола Миколаєвич
Лозенко Альберт Федорович
Рябченко Сергій Михайлович
Терлецький Олег Валентинович
Чорноморець Надія Федорівна
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2020-04-02
