scholarly journals Calculation of the Amplitude of Acoustic Waves in Nanoscale Magnets in an Alternating Magnetic Field Caused by Displacements of Domain Boundaries

2021 ◽  
pp. 47-52
Author(s):  
L.P. Petrova ◽  
N.M. Ignatenko ◽  
A.S. Gromkov
Keyword(s):  
Magnetic Field ◽  
Absorption Coefficient ◽  
Wave Vector ◽  
Carrier Frequency ◽  
Acoustic Waves ◽  
Spontaneous Magnetization ◽  
Alternating Magnetic Field ◽  
Internal Stresses ◽  
Generation Process ◽  
Domain Boundaries

This paper proposes an algorithm that utilizes a macroscopic approach to calculate the amplitude of the total acoustic signal generated by an alternating magnetic field in ribbon-shaped nanocrystalline magnets (NCMs) with polydomain nanofibers at reversible displacements of domain boundaries. The calculations are made for the case with the wave vector directed along the magnetic field parallel to the tape plane. At the same time, the influence of anharmonicity on the displacements of the domain boundaries is considered for the carrier frequency. The orientation and frequency dependences for the wave vector and the signal absorption coefficient are found under the assumption that the rotation processes can be neglected. It is shown that the residual internal stresses in the (poly- or monodomain) nanograin NCMs have a significant effect on the absorption coefficient and the amplitude of the generated DG signal. The magnetic anisotropy constants decrease along with the size of the nanograins. In this case, the generation process due to the rotation of the spontaneous magnetization vectors is also significant, which must be considered in relation to the displacement processes. The proposed algorithm for calculating the amplitudes of the signals generated by a nanocrystalline magnet can be used to predict the friction properties of the developed promising NCM and calculate the amplitudes of the generated signals at the carrier frequency and harmonics.

Magnetic Field Dependent Damping of Magnetic Particle Filled Polypropylene

2012 ◽  
Vol 184 ◽  
pp. 449-454
Author(s):  
O.A. Lambri ◽  
D. Gargicevich ◽  
F. Tarditti ◽  
F.G. Bonifacich ◽  
Werner Riehemann ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Elastic Modulus ◽  
Internal Friction ◽  
Polymer Matrix ◽  
Volume Fraction ◽  
Alternating Magnetic Field ◽  
Internal Stresses ◽  
Dynamic Shear Modulus ◽  
Dc Magnetic Field ◽  
Damaged Zone

The behavior of internal friction Q-1 and dynamic shear modulus has been studied in polypropylene charged with either different volume fraction or size of magnetite (Fe3O4) particles, as a function of the applied magnetic field at 318 K. An increase of the alternating (AC) magnetic field oscillating with 50 Hz, leads to an increase of the internal friction. In addition, during the subsequently decreasing alternating magnetic field, the internal friction decreases, but a hysteretic behavior appeared. In fact, the internal friction of the decreasing part of magnetic field amplitude is found to be smaller than during the previously increasing amplitude part of the treatment with the alternating magnetic field. Subsequent magnetic treatment cycles, lead to successively decreasing internal friction. In contrast, during the increase of a direct (DC) magnetic field, the internal friction decreases and the elastic modulus increases. The behavior of the internal friction and the elastic modulus during the application of an oscillating magnetic field (AC) is discussed on the basis of the development of both, a new zone with different rheological characteristics than the matrix but of the same material (self-inclusion), and/or a deteriorated or damaged zone (chain’s cuts) of the polymer matrix in the neighborhood of the magnetite inclusion. These effects are promoted by the movement or small relative rotation of the magnetite particles related to the surrounding matrix controlled by the oscillating field. The behavior of the internal friction and elastic modulus during the application of a direct (DC) magnetic field is discussed on the basis of the increase of the internal stresses into the polymer matrix due to the promotion of the magnetomechanical stresses.

scholarly journals Heat induction in two-dimensional graphene–Fe3O4 nanohybrids for magnetic hyperthermia applications with artificial neural network modeling

RSC Advances ◽  
2021 ◽  
Vol 11 (35) ◽  
pp. 21702-21715
Author(s):  
M. S. Dar ◽  
Khush Bakhat Akram ◽  
Ayesha Sohail ◽  
Fatima Arif ◽  
Fatemeh Zabihi ◽  
...  
Keyword(s):  
Neural Network ◽  
Magnetic Field ◽  
Artificial Neural Network ◽  
Network Modeling ◽  
Magnetic Hyperthermia ◽  
Alternating Magnetic Field ◽  
Neural Network Modeling ◽  
Two Dimensional ◽  
Artificial Neural Network Modeling ◽  
Heat Induction

Synthesis of Fe3O4–graphene (FG) nanohybrids and magnetothermal measurements of FxG100–x (x = 0, 25, 45, 65, 75, 85, 100) nanohybrids (25 mg each) at a 633 kHz alternating magnetic field of strength 9.1 mT.

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