scholarly journals Влияние внешних факторов на ширину линии ферромагнитного резонанса в структурах с обменным смещением

2021 ◽  
Vol 63 (6) ◽  
pp. 693
Author(s):  
И.О. Джунь ◽  
Г.В. Бабайцев ◽  
М.Г. Козин ◽  
И.Л. Ромашкина ◽  
Е.И. Шанова ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Line Width ◽  
Exchange Bias ◽  
Uniaxial Anisotropy ◽  
Ferromagnetic Layer ◽  
Constant Thickness ◽  
Extrinsic Factors ◽  
Layer Sequence ◽  
Average Size ◽  
A Minor

Extrinsic factors contributing to the ferromagnetic resonance (FMR) line width in double layer (ferromagnet/antiferromagnet) systems with exchange bias were investigated. Dependence of the FMR line width on the thickness of the antiferromagnetic (AF) layer at a constant thickness of the ferromagnetic (F) layer and layers deposition order of the F - and AF - layers, as well as the correlation between the exchange bias and the surface roughness of the sample were studied. We found that the exchange bias has a minor, if any, contribution to the line width. In systems with an antiferromagnet deposited on a ferromagnetic layer, the width of the FMR line increases in proportion to the average size of the surface roughness. In systems with reversal layer sequence the uniaxial anisotropy provides a significant contribution to the line width. The width of the FMR line is in a quadratic dependence on the uniaxial anisotropy and inversely proportional to the thickness of the antiferromagnetic layer, which can be attributed to the effect of the microstructure evolution with the thickness as an extrinsic factor in the damping of the FMR.

scholarly journals Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
F. G. Silva ◽  
J. Depeyrot ◽  
Yu. L. Raikher ◽  
V. I. Stepanov ◽  
I. S. Poperechny ◽  
...  
Keyword(s):  
Spin Glass ◽  
Magnetic Moment ◽  
Exchange Bias ◽  
Uniaxial Anisotropy ◽  
Thermal Fluctuations ◽  
High Amplitude ◽  
Spin Coupling ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Core Shell Nanoparticles

AbstractExchange bias properties of MnFe$$_2$$ 2 O$$_4$$ 4 @$$\gamma$$ γ –Fe$$_2$$ 2 O$$_3$$ 3 core–shell nanoparticles are investigated. The measured field and temperature dependencies of the magnetization point out a well-ordered ferrimagnetic core surrounded by a layer with spin glass-like arrangement. Quasi-static SQUID magnetization measurements are presented along with high-amplitude pulse ones and are cross-analyzed by comparison against ferromagnetic resonance experiments at 9 GHz. These measurements allow one to discern three types of magnetic anisotropies affecting the dynamics of the magnetic moment of the well-ordered ferrimagnetic NP’s core viz. the easy-axis (uniaxial) anisotropy, the unidirectional exchange-bias anisotropy and the rotatable anisotropy. The uniaxial anisotropy originates from the structural core–shell interface. The unidirectional exchange-bias anisotropy is associated with the spin-coupling at the ferrimagnetic/spin glass-like interface; it is observable only at low temperatures after a field-cooling process. The rotatable anisotropy is caused by partially-pinned spins at the core/shell interface; it manifests itself as an intrinsic field always parallel to the external applied magnetic field. The whole set of experimental results is interpreted in the framework of superparamagnetic theory, i.e., essentially taking into account the effect of thermal fluctuations on the magnetic moment of the particle core. In particular, it is found that the rotatable anisotropy of our system is of a uniaxial type.

scholarly journals Hydrothermal Synthesis of Hematite Nanoparticles Decorated on Carbon Mesospheres and Their Synergetic Action on the Thermal Decomposition of Nitrocellulose

Nanomaterials ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 968 ◽  
Author(s):  
Abdenacer Benhammada ◽  
Djalal Trache ◽  
Mohamed Kesraoui ◽  
Salim Chelouche
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Analytical Techniques ◽  
Decomposition Reaction ◽  
Decomposition Temperature ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Nano Catalyst ◽  
Average Size ◽  
A Minor

In this study, carbon mesospheres (CMS) and iron oxide nanoparticles decorated on carbon mesospheres (Fe2O3-CMS) were effectively synthesized by a direct and simple hydrothermal approach. α-Fe2O3 nanoparticles have been successfully dispersed in situ on a CMS surface. The nanoparticles obtained have been characterized by employing different analytical techniques encompassing Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The produced carbon mesospheres, mostly spherical in shape, exhibited an average size of 334.5 nm, whereas that of Fe2O3 supported on CMS is at around 80 nm. The catalytic effect of the nanocatalyst on the thermal behavior of cellulose nitrate (NC) was investigated by utilizing differential scanning calorimetry (DSC). The determination of kinetic parameters has been carried out using four isoconversional kinetic methods based on DSC data obtained at various heating rates. It is demonstrated that Fe2O3-CMS have a minor influence on the decomposition temperature of NC, while a noticeable diminution of the activation energy is acquired. In contrast, pure CMS have a slight stabilizing effect with an increase of apparent activation energy. Furthermore, the decomposition reaction mechanism of NC is affected by the introduction of the nano-catalyst. Lastly, we can infer that Fe2O3-CMS may be securely employed as an effective catalyst for the thermal decomposition of NC.

Nonvolatile Electric Control of Exchange Bias by a Redox Transformation of the Ferromagnetic Layer

2019 ◽  
Vol 5 (6) ◽  
pp. 1900296 ◽  
Author(s):  
Jonas Zehner ◽  
Rico Huhnstock ◽  
Steffen Oswald ◽  
Ulrike Wolff ◽  
Ivan Soldatov ◽  
...  
Keyword(s):  
Exchange Bias ◽  
Ferromagnetic Layer ◽  
Redox Transformation ◽  
Electric Control

Fabrication of Injection Moulded 304L Stainless Steels Reinforced with Tungsten Carbide Particles

2012 ◽  
Vol 706-709 ◽  
pp. 638-642 ◽  
Author(s):  
Nutthita Chuankrerkkul ◽  
Parinya Chakartnarodom
Keyword(s):  
Tungsten Carbide ◽  
Sintering Temperature ◽  
Hydrogen Atmosphere ◽  
Powder Injection ◽  
304L Stainless Steel ◽  
Water Leaching ◽  
Powder Injection Moulding ◽  
Average Size ◽  
A Minor ◽  
Carbide Particles

Powder injection moulding of 304L stainless steel - tungsten carbide (WC) composites were carried out in the present work. Two different WC particle i.e. WC having average size of 4.8 µm and 1.6 µm were used. Feedstock of powder loading up to 55 vol% were successfully prepared using binder composed mainly of polyethylene glycol (PEG) and a minor constituent of polymethylmethacrylate (PMMA). The mouldings were leached in water at temperatures of 40 °C and 60 °C from 30 minutes to 24 hours in order to study the effect of leaching conditions on the removal of the PEG. The remaining binder, PMMA, provided strength to the mouldings after leaching of the PEG and it could be removed by pyrolysis during ramping up to the sintering temperature. Specimens were sintered under hydrogen atmosphere at 1250 °C for 1 hour. Sintered components were subjected to testing and characterisation. Scanning electron microscope was used to observe microstructure of specimens after moulding, leaching and sintering. It was found that the hardness of the sintered specimens increased with either increasing the amount of the powder loading in the feedstock or reducing the average size of WC in the powder mixture. In addition, the water leaching of the PEG linearly correlates with the natural log of time and the equation predicts that PEG will be removed completely in 11.24 ± 1.31 hours which corresponds with the experiment result that PEG completely removed in 12 hours.

A unified theory of surface roughness

1984 ◽  
Vol 393 (1804) ◽  
pp. 133-157 ◽  
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Random Noise ◽  
Sampling Interval ◽  
The Other ◽  
Real Surface ◽  
Unified Theory ◽  
Two Dimensional ◽  
Minor Degree ◽  
A Minor

The properties of the peaks and summits of a rough surface are predicted on the assumption that the surface is two-dimensional random noise. The important result is that, in non-dimensional form, the answers depend only to a minor degree on the parameters describing the surface or on the sampling interval used: on the other hand the absolute values are strongly dependent on the sampling interval. Experimental results on a real surface agree remarkably well with the predictions.

Observation of Ag Precipitate in CuAgZr Alloy during In Situ High Temperature TEM

2017 ◽  
Vol 263 ◽  
pp. 50-54
Author(s):  
Waraporn Piyawit ◽  
Panya Buahombura
Keyword(s):  
High Temperature ◽  
Heating Process ◽  
Minor Variation ◽  
Transmission Electron ◽  
Large Lattice ◽  
Dislocation Movement ◽  
Higher Temperature ◽  
Average Size ◽  
A Minor

CuAgZr alloy is a minor variation of CuAg alloy that is remarkably known for good combination of strength and electrical conductivity. Strengthening and conductivity enhancing of CuAgZr alloy is essentially proficient by the precipitation of Ag precipitates. The behavior of Ag precipitates at high temperature was investigated using in-situ transmission electron microscopy. These nanoscale Ag precipitates are formed in CuAgZr alloy during heating process with the average size of 5 nm. Growth of precipitates at higher temperature can be explained by the consumption of solute diffusing from smaller precipitates. Dislocation looping at high temperature would be the effects of a large lattice strain along matrix/precipitate interface that would retard the dislocation movement.

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