Anisotropic self-assemblies of magnetic nanoparticles: experimental evidence of low-field deviation from the linear response theory and empirical model

Nanoscale ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 572-583 ◽  
Author(s):  
Irene Andreu ◽  
Ainhoa Urtizberea ◽  
Eva Natividad
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Linear Response ◽  
Relaxation Times ◽  
Linear Response Theory ◽  
Field Amplitude ◽  
Interactive Behavior ◽  
Low Field ◽  
Physical Effects ◽  
Néel Relaxation

Anisotropic assemblies of magnetic nanoparticles with a collective-interactive behavior that can be tuned by an alternating magnetic field amplitude display a cascade of unexpected physical effects and allow reformulation of Néel relaxation times.

scholarly journals Heating Efficiency of Triple Vortex State Cylindrical Magnetic Nanoparticles

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
De Wei Wong ◽  
Wei Liang Gan ◽  
Yuan Kai Teo ◽  
Wen Siang Lew
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Magnetic Fields ◽  
Vortex State ◽  
Magnetic Hyperthermia ◽  
Relaxation Mechanism ◽  
Micromagnetic Simulations ◽  
Heating Efficiency ◽  
Aspect Ratios ◽  
Low Field

AbstractA well-established method for treating cancerous tumors is magnetic hyperthermia, which uses localized heat generated by the relaxation mechanism of magnetic nanoparticles (MNPs) in a high-frequency alternating magnetic field. In this work, we investigate the heating efficiency of cylindrical NiFe MNPs, fabricated by template-assisted pulsed electrodeposition combined with differential chemical etching. The cylindrical geometry of the MNP enables the formation of the triple vortex state, which increases the heat generation efficiency by four times. Using time-dependent calorimetric measurements, the specific absorption rate (SAR) of the MNPs was determined and compared with the numerical calculations from micromagnetic simulations and vibrating sample magnetometer measurements. The magnetization reversal of high aspect ratios MNPs showed higher remanent magnetization and low-field susceptibility leading to higher hysteresis losses, which was reflected in higher experimental and theoretical SAR values. The SAR dependence on magnetic field strength exhibited small SAR values at low magnetic fields and saturates at high magnetic fields, which is correlated to the coercive field of the MNPs and a characteristic feature of ferromagnetic MNPs. The optimization of cylindrical NiFe MNPs will play a pivotal role in producing high heating performance and biocompatible magnetic hyperthermia agents.

Linear Response Theory for a Degenerate Electron Gas in a Strong Magnetic Field

1969 ◽  
Vol 177 (3) ◽  
pp. 1019-1036 ◽  
Author(s):  
Michael P. Greene ◽  
Hyung Joon Lee ◽  
J. J. Quinn ◽  
Sergio Rodriguez
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Linear Response ◽  
Electron Gas ◽  
Linear Response Theory ◽  
Degenerate Electron ◽  
Response Theory ◽  
Degenerate Electron Gas

scholarly journals Investigation of Magneto-phonon Resonance in Graphene Monolayers

2017 ◽  
Vol 33 (4) ◽  
Author(s):  
Bui Dinh Hoi
Keyword(s):  
Magnetic Field ◽  
Linear Response ◽  
Resonant Scattering ◽  
Linear Response Theory ◽  
Landau Levels ◽  
Effect Of Temperature ◽  
Perpendicular Magnetic Field ◽  
Dirac Fermions ◽  
Deformation Potential ◽  
The Magnetic Field

In this work, utilising the linear response theory we calculate the magneto conductivity (MC) in graphene monolayers, subjected to a static perpendicular magnetic field. The interaction of Dirac fermions with optical phonon via deformation potential is taken into account at high temperature. The dependence of the MC on the magnetic field shows resonant peaks that describe transitions of electrons between Landau levels via the resonant scattering with optical phonons. The effect of temperature on the MC is also obtained and discussed.

Dependence of Brownian and Néel relaxation times on magnetic field strength

2013 ◽  
Vol 41 (1) ◽  
pp. 012301 ◽  
Author(s):  
Robert J. Deissler ◽  
Yong Wu ◽  
Michael A. Martens
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Relaxation Times ◽  
Néel Relaxation

Analytical modeling of hyperthermia using magnetic nanoparticles

2018 ◽  
Vol 81 (3) ◽  
pp. 30901
Author(s):  
Mohamed Nassim Bensenane ◽  
Assia Rachida Senoudi ◽  
Reda Benmouna ◽  
Fouzia Ould-Kaddour
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Heat Equation ◽  
Analytical Modeling ◽  
Volume Fraction ◽  
Biological Properties ◽  
Field Amplitude ◽  
Minimal Damage ◽  
Pennes Model ◽  
Analytical Resolution

Hyperthermia using magnetic nanoparticles (MNPs) is one of many techniques to treat cancer causing minimal damage to healthy tissues. In the present work we give an analytical resolution of the bio-heat equation (based on Pennes model) providing the temperature rise as a function of the characteristics of the magnetic nanoparticles, the applied magnetic field and the biological properties of the tissue. The temperature inside the tumor was found to be very sensitive to the frequency f of alternating magnetic field, magnetic field amplitude H0 and volume fraction φ. This study optimizes the intensity of magnetic field to reach ideal hyperthermia conditions. When f varies between 50 and 150 KHz, temperature increases from 39 °C until 53 °C; when H0 is ranged from 5 − 15 kA/m, it increases from 39.5 °C until 49 °C, and when volume fraction φ of MNPs is ranged from 2 × 10−4 to  3 × 10−4 it increases from 44 °C until 48 °C.

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