The role of dipolar interactions in magnetic nanoparticles: Ferromagnetic resonance in discontinuous magnetic multilayers

2007 ◽  
Vol 101 (10) ◽  
pp. 103907 ◽  
Author(s):  
D. S. Schmool ◽  
R. Rocha ◽  
J. B. Sousa ◽  
J. A. M. Santos ◽  
G. N. Kakazei ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
Ferromagnetic Resonance ◽  
Magnetic Multilayers ◽  
Dipolar Interactions

Dipolar Interaction Effects in the Magnetic and Magnetotransport Properties of Ordered Nanoparticle Arrays

2008 ◽  
Vol 8 (6) ◽  
pp. 2929-2943 ◽  
Author(s):  
D. Kechrakos ◽  
K. N. Trohidou
Keyword(s):  
Magnetic Nanoparticles ◽  
Structural Parameters ◽  
Dipolar Interaction ◽  
Interaction Effects ◽  
Blocking Temperature ◽  
Dipolar Interactions ◽  
Interparticle Interactions ◽  
Ordered Arrays ◽  
Monte Carlo Studies

Assemblies of magnetic nanoparticles exhibit interesting physical properties arising from the competition of intraparticle dynamics and interparticle interactions. In ordered arrays of magnetic nanoparticles magnetostatic interparticle interactions introduce collective dynamics acting competitively to random anisotropy. Basic understanding, characterization and control of dipolar interaction effects in arrays of magnetic nanoparticles is an issue of central importance. To this end, numerical simulation techniques offer an indispensable tool. We report on Monte Carlo studies of the magnetic hysteresis and spin-dependent transport in thin films formed by ordered arrays of magnetic nanoparticles. Emphasis is given to the modifications of the single-particle behavior due to interparticle dipolar interactions as these arise in quantities of experimental interest, such as, the magnetization, the susceptibility and the magnetoresistance. We investigate the role of the structural parameters of an array (interparticle separation, number of stacked monolayers) and the role of the internal structure of the nanoparticles (single phase, core–shell). Dipolar interactions are responsible for anisotropic magnetic behavior between the in-plane and out-of-plane directions of the sample, which is reflected on the investigated magnetic properties (magnetization, transverse susceptibility and magnetoresistance) and the parameters of the array (remanent magnetization, coercive field, and blocking temperature). Our numerical results are compared to existing measurements on self-assembled arrays of Fe-based and Co nanoparticles is made.

Ferromagnetic Resonance Biosensor for Homogeneous and Volumetric Detection of DNA

2017 ◽  
Author(s):  
Bo Tian ◽  
Peter Svedlindh ◽  
Mattias Strömberg ◽  
Erik Wetterskog
Keyword(s):  
Magnetic Nanoparticles ◽  
Ferromagnetic Resonance ◽  
Limit Of Detection ◽  
Point Of Care ◽  
Rolling Circle Amplification ◽  
Resonance Field ◽  
Isothermal Amplification ◽  
Detection Sensitivity ◽  
Serum Samples ◽  
Rolling Circle

In this work, we demonstrate for the first time, a ferromagnetic resonance (FMR) based homogeneous and volumetric biosensor for magnetic label detection. Two different isothermal amplification methods, <i>i.e.</i>, rolling circle amplification (RCA) and loop-mediated isothermal amplification (LAMP) are adopted and combined with a standard electron paramagnetic resonance (EPR) spectrometer for FMR biosensing. For RCA-based FMR biosensor, binding of RCA products of a synthetic Vibrio cholerae target DNA sequence gives rise to the formation of aggregates of magnetic nanoparticles. Immobilization of nanoparticles within the aggregates leads to a decrease of the net anisotropy of the system and a concomitant increase of the resonance field. A limit of detection of 1 pM is obtained with an average coefficient of variation of 0.16%, which is superior to the performance of other reported RCA-based magnetic biosensors. For LAMP-based sensing, a synthetic Zika virus target oligonucleotide is amplified and detected in 20% serum samples. Immobilization of magnetic nanoparticles is induced by their co-precipitation with Mg<sub>2</sub>P<sub>2</sub>O<sub>7</sub> (a by-product of LAMP) and provides a detection sensitivity of 100 aM. The fast measurement, high sensitivity and miniaturization potential of the proposed FMR biosensing technology makes it a promising candidate for designing future point-of-care devices.<br>

Role of Dipolar Interactions on the Thermal Stability of High-Density Bit-Patterned Media

2012 ◽  
Vol 3 ◽  
pp. 4500204-4500204 ◽  
Author(s):  
N. Eibagi ◽  
J. J. Kan ◽  
F. E. Spada ◽  
E. E. Fullerton
Keyword(s):  
Thermal Stability ◽  
High Density ◽  
Dipolar Interactions ◽  
Bit Patterned Media ◽  
Patterned Media ◽  
Thermal Stability Of

Lorentz microscopy sheds light on the role of dipolar interactions in magnetic hyperthermia

Nanoscale ◽  
2015 ◽  
Vol 7 (17) ◽  
pp. 7717-7725 ◽  
Author(s):  
M. Campanini ◽  
R. Ciprian ◽  
E. Bedogni ◽  
A. Mega ◽  
V. Chiesi ◽  
...  
Keyword(s):  
Magnetic Hyperthermia ◽  
Dipolar Interactions ◽  
Magnetic Characterization ◽  
Lorentz Microscopy

Left: morphological and magnetic characterization of magnetite NPs. Right: Lorentz microscopy unveils the role of dipolar interactions in magnetic hyperthermia of superparamagnetic NPs.

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