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1.
ACS Sens ; 6(12): 4315-4324, 2021 12 24.
Artigo em Inglês | MEDLINE | ID: mdl-34842420

RESUMO

The effect of the stray field of Fe/Fe3O4 nanoparticles on the angular dependence of the microwave absorption derivative in CoFeB/Ta/CoFeB synthetic ferrimagnetic structures and CoFeB films with perpendicular anisotropy is analyzed, and its application for sensor technology is proposed. The effective field of the "platform-particles" system controlled by the magnetic dipole interaction of the CoFeB-Fe/Fe3O4 system decreased to zero in areas where the platform was magnetostatically coupled with nanoparticles. Micromagnetic modeling demonstrated the distribution of magnetization and resistance in local areas of CoFeB/Ta/CoFeB structures under the nanoparticles. The microwave absorption derivative can be used as an indicator of local magnetization switching of the giant magnetoresistance (GMR) structure under scattering fields of NPs or magnetically labeled cells. The limiting sensitivity of the detection method was 2.4 × 107 nanoparticles, which covered the spin-valve surface. We have proposed to combine the advantages of a GMR sensor with wireless technology of microwave reading of magnetoresistance for the detection of magnetically labeled cells.


Assuntos
Micro-Ondas , Nanopartículas , Magnetismo , Imãs
2.
Langmuir ; 36(30): 8680-8686, 2020 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-32631066

RESUMO

A mixture of water suspensions of graphene oxide (GO) and polytetrafluoroethylene (PTFE) was used to make the films GO-PTFE (50:50). They became conductive (2.0-2.8 S/cm) while maintaining flexibility after reduction with hydrazine and subsequent annealing at 370 °C. The structure and morphology of the reduced films (rGO-PTFE) are examined in detail by means of a number of techniques such as scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Raman, and contact angle wetting. The results of the films tested as current collectors in a metal-free supercapacitor with electrodes from microwave exfoliated GO and an acid (1 M H2SO4) electrolyte are presented.

3.
J Phys Condens Matter ; 31(8): 085801, 2019 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-30628583

RESUMO

Effect of the delay between stabilization of magnetic field and recording of the reversal curve on the first order reversal curves (FORC) has been found and analyzed in K0.4[Cr(CN)6][Mn(R/S)-pn](R/S)-pnH0.6 chiral magnet. The difference between the 'delayed' and 'on time' FORC diagrams manifests the effect of magnetic relaxation on switching field of the nonlinear spin configurations presented in crystals (spin solitons, domain walls, etc). The domain walls and spin solitons with different relaxation rates contribute to reversal magnetization. The temperature dependence of magnetic anisotropy governing nonlinear spin excitations is discussed in the frames of the Callen-Callen formalism.

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