scholarly journals Disorder-Induced Transformation of the Energy Landscapes and Magnetization Dynamics in Two-Dimensional Ensembles of Dipole-Coupled Magnetic Nanoparticles

2020 ◽  
Vol 10 (2) ◽  
Author(s):  
David Gallina ◽  
G. M. Pastor
Keyword(s):  
Magnetic Nanoparticles ◽  
Two Dimensional ◽  
Energy Landscapes ◽  
Magnetization Dynamics

scholarly journals Structural Disorder and Collective Behavior of Two-Dimensional Magnetic Nanostructures

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1392
Author(s):  
David Gallina ◽  
G. M. Pastor
Keyword(s):  
Interaction Energy ◽  
Time Evolution ◽  
Magnetic Nanostructures ◽  
Thermal Quenching ◽  
Structural Disorder ◽  
Square Lattice ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Two Dimensional ◽  
Energy Landscapes

Structural disorder has been shown to be responsible for profound changes of the interaction-energy landscapes and collective dynamics of two-dimensional (2D) magnetic nanostructures. Weakly-disordered 2D ensembles have a few particularly stable magnetic configurations with large basins of attraction from which the higher-energy metastable configurations are separated by only small downward barriers. In contrast, strongly-disordered ensembles have rough energy landscapes with a large number of low-energy local minima separated by relatively large energy barriers. Consequently, the former show good-structure-seeker behavior with an unhindered relaxation dynamics that is funnelled towards the global minimum, whereas the latter show a time evolution involving multiple time scales and trapping which is reminiscent of glasses. Although these general trends have been clearly established, a detailed assessment of the extent of these effects in specific nanostructure realizations remains elusive. The present study quantifies the disorder-induced changes in the interaction-energy landscape of two-dimensional dipole-coupled magnetic nanoparticles as a function of the magnetic configuration of the ensembles. Representative examples of weakly-disordered square-lattice arrangements, showing good structure-seeker behavior, and of strongly-disordered arrangements, showing spin-glass-like behavior, are considered. The topology of the kinetic networks of metastable magnetic configurations is analyzed. The consequences of disorder on the morphology of the interaction-energy landscapes are revealed by contrasting the corresponding disconnectivity graphs. The correlations between the characteristics of the energy landscapes and the Markovian dynamics of the various magnetic nanostructures are quantified by calculating the field-free relaxation time evolution after either magnetic saturation or thermal quenching and by comparing them with the corresponding averages over a large number of structural arrangements. Common trends and system-specific features are identified and discussed.

scholarly journals Empirical Expression for AC Magnetization Harmonics of Magnetic Nanoparticles under High-Frequency Excitation Field for Thermometry

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2506
Author(s):  
Zhongzhou Du ◽  
Dandan Wang ◽  
Yi Sun ◽  
Yuki Noguchi ◽  
Shi Bai ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
High Frequency ◽  
Planck Equation ◽  
Magnetization Dynamics ◽  
Excitation Field ◽  
Fokker Planck Equation ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Ac Magnetization ◽  
Fokker Planck

The Fokker–Planck equation accurately describes AC magnetization dynamics of magnetic nanoparticles (MNPs). However, the model for describing AC magnetization dynamics of MNPs based on Fokker-Planck equation is very complicated and the numerical calculation of Fokker-Planck function is time consuming. In the stable stage of AC magnetization response, there are differences in the harmonic phase and amplitude between the stable magnetization response of MNPs described by Langevin and Fokker–Planck equation. Therefore, we proposed an empirical model for AC magnetization harmonics to compensate the attenuation of harmonics amplitude induced by a high frequency excitation field. Simulation and experimental results show that the proposed model accurately describes the AC M–H curve. Moreover, we propose a harmonic amplitude–temperature model of a magnetic nanoparticle thermometer (MNPT) in a high-frequency excitation field. The simulation results show that the temperature error is less than 0.008 K in the temperature range 310–320 K. The proposed empirical model is expected to help improve MNPT performance.

scholarly journals Quantification of magnetic nanoparticles by compensating for multiple environment changes simultaneously

Nanoscale ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 195-200 ◽  
Author(s):  
Yipeng Shi ◽  
Dhrubo Jyoti ◽  
Scott W. Gordon-Wylie ◽  
John B. Weaver
Keyword(s):  
Magnetic Nanoparticles ◽  
Two Dimensional ◽  
Scaling Method ◽  
Environment Changes ◽  
Dimensional Scaling

A novel two-dimensional scaling method is demonstrated to improve the accuracy of nanoparticle quantification when multiple effects are present.

scholarly journals Simulations of super-structure domain walls in two dimensional assemblies of magnetic nanoparticles

2015 ◽  
Vol 118 (4) ◽  
pp. 043901 ◽  
Author(s):  
J. Jordanovic ◽  
M. Beleggia ◽  
J. Schiøtz ◽  
C. Frandsen
Keyword(s):  
Magnetic Nanoparticles ◽  
Domain Walls ◽  
Two Dimensional ◽  
Super Structure ◽  
Structure Domain

Two-dimensional optical trapping and clustering of magnetic nanoparticles

2014 ◽  
Vol 44 (6) ◽  
pp. 557-563 ◽  
Author(s):  
XiaoHong YANG ◽  
WuYi ZHOU ◽  
ChengYun ZHANG ◽  
HaiDong DENG ◽  
ZiZheng GUO
Keyword(s):  
Magnetic Nanoparticles ◽  
Optical Trapping ◽  
Two Dimensional

scholarly journals Dynamics of interacting magnetic nanoparticles: effective behavior from competition between Brownian and Néel relaxation

2020 ◽  
Vol 22 (39) ◽  
pp. 22244-22259
Author(s):  
Patrick Ilg ◽  
Martin Kröger
Keyword(s):  
Monte Carlo ◽  
Magnetic Nanoparticles ◽  
Monte Carlo Method ◽  
Computer Simulations ◽  
Brownian Dynamics ◽  
Magnetization Dynamics ◽  
Steric Interactions ◽  
Néel Relaxation ◽  
Effective Behavior

We identify the influence of dipolar and steric interactions on the Brownian and Néel contributions to the magnetization dynamics of magnetic nanoparticles from extensive computer simulations using a combined Brownian dynamics/Monte-Carlo method.

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