Thermal hysteresis of superparamagnetic Gd nanoparticle clusters

Souza, C. M.; Pedrosa, Sílvia Santos; Carriço, A. S.; Rebouças, G. O. G.; Dantas, Ana L.

doi:10.1103/physrevb.99.174441

Cited by 4 publications

(9 citation statements)

References 22 publications

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“…The TEM results (Figures 4–6) and the broadband‐frequency dependence χ(f) (Figure 7) provide the crucial clue to understand the key mechanism of magnetic differences. Close contact of nanoparticles within aggregates causes magnetostatic interaction between them, leading to larger effective grain sizes in terms of the domain state behavior than the physical size of the individual particles, as it is shown by theoretical models and experimental data studying such kind of ultrafine particle assemblages (Chen et al, 2008; Mørup et al, 2010; Souza et al, 2019). According to these results, variable arrangement of nanoparticles within different aggregates in the red soil and the Caohai Lake sediments will lead to a wide distribution of the effective grain sizes throughout the SP range, which can tail into the range of SSD behavior as shown by the cited works above.…”

Section: Discussionmentioning

confidence: 96%

Nano‐Magnetite Aggregates in Red Soil on Low Magnetic Bedrock, Their Changes During Source‐Sink Transfer, and Implications for Paleoclimate Studies

Zhang

Appel

et al. 2020

JGR Solid Earth

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Soil and lake sediments are important paleoclimate archives often forming a source-sink setting. To better understand magnetic properties in such settings, we studied red soil on low-magnetic bedrock and subrecent sediments of Caohai Lake (CL) in Heqing Basin, China. Red soil is the only important source material for the CL sediments, it is highly magnetic with susceptibilities (χ) of~10 −5 m 3 /kg. The red soil is dominated by pedogenic nano-magnetite (~10-15 nm) arranged in aggregates of~100 nm, with particle interaction that causes a wide effective grain size distribution in the superparamagnetic (SP) range tailing into stable single-domain behavior. Transmission electron microscopy and broadband frequency χ(f) suggest partial disintegration of the aggregates and increased alteration of the nanoparticles to hematite during transfer of red soil material to CL. This shifts the domain state behavior to smaller effective magnetic grain sizes, resulting in lower χ fd % and χ values, and a characteristic change of χ(f). The SP-stable single-domain distribution of the aggregates in red soil could be climate dependent, and the ratio of saturation remanence to χ is a potential bedrock-specific paleoclimate proxy reflecting it. Magnetic properties of the CL sediments are controlled by an assemblage of nanoparticle aggregates and larger-sized bedrock-derived magnetite. The results challenge the validity of the previous paleoclimate interpretation from the 168-m-long Core-HQ (900-30 ka) in Heqing Basin. Disintegration of aggregates could lead to SP behavior with low χ fd % without extinction of individual magnetite nanoparticles, and the χ fd %-based assumption of SP magnetite dissolution may be wrong.

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Section: Discussionmentioning

confidence: 96%

Nano‐Magnetite Aggregates in Red Soil on Low Magnetic Bedrock, Their Changes During Source‐Sink Transfer, and Implications for Paleoclimate Studies

Zhang

Appel

et al. 2020

JGR Solid Earth

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“…In natural samples, particles typically exist in variable sizes, often aggregated in clusters of SP and SSD particles with anisotropic dipolar fields comparable to the settings of Souza et al. (2019), Dantas et al. (2007) and Liubimova et al.…”

Section: Discussionmentioning

confidence: 97%

“…We hypothesize that the thermal hysteresis of the studied samples results from dipolar coupling effects, which based on Pedrosa et al (2018) can modulate the hump-shaped thermal dependency of thermal relaxation, without eliminating SP characteristics of the individual particles (Andersson et al, 2016;Chen et al, 2008;Schmool & Kachkachi, 2016;Souza et al, 2019). Thus, a hump in κ-T curves could exist even in samples where all particles are coupled.…”

Section: Origin Of the Thermal Hysteresismentioning

confidence: 98%

“…They showed that coupled nanoparticle moments can be stable in varying external fields, but low external field changes of few hundred A/m can also cause large magnetization changes. In natural samples, particles typically exist in variable sizes, often aggregated in clusters of SP and SSD particles with anisotropic dipolar fields comparable to the settings of Souza et al (2019), Dantas et al (2007) and Liubimova et al (2017). In part of these clusters, the dipolar coupling could be outweighed by the external field of the MFK1, causing changes in the directional arrangement of particle moments.…”

Section: Origin Of the Thermal Hysteresismentioning

confidence: 99%

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Reversible Thermal Hysteresis in Heating‐Cooling Cycles of Magnetic Susceptibility: A Fine Particle Effect of Magnetite

Zhang

Appel

2023

Geophysical Research Letters

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“…In other cases, if the MNPs form a linear chain, the dipolar interaction favours head to the tail arrangement of magnetic moments [26]. In these contexts, there are several works which have incorporated the effect of dipolar interaction [27][28][29][30][31]. For example, using experiments and analytical methods, Allia et al studied the dipolar interaction effect on hysteresis in granular magnetic systems [29].…”

Section: Introductionmentioning

confidence: 99%

Tailoring Heat Dissipation in Ordered Arrays of Dipolar Coupled Magnetic Nanoparticles

Anand

2021

Preprint

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The main aim of the present work is to analyse the effect of dipolar interaction strength λ, particle size D and temperature T on the hysteresis mechanism in ordered arrays of magnetic nanoparticles (MNPs) using computer simulations. The anisotropy axes of the MNPs are assumed to have random orientation to mimic the real system. In the absence of thermal fluctuations and dipolar interaction, the hysteresis follows the Stoner and Wohlfarth model irrespective of D, as expected. The hysteresis loop area is minimal for particle sizes D ≈ 8 − 16 nm at T = 300 K and λ = 0.0, indicating the dominance of superparamagnetic character. Switching magnetic interaction on is able to move the MNPs from superparamagnetic to a ferromagnetic state even at room temperature; therefore, magnetic interaction of enough strength enhances the hysteresis loop area. Interestingly, the hysteresis loop area is significant and is the same as that of Stoner and Wohlfarth particle even T = 300 K and negligible dipolar interaction for ferromagnetic MNPs (D > 16 nm). The coercive field µ o H c and blocking temperature T B also get enhanced with an increase in λ and D. The rigorous analysis of the coercive field µ o H c vs temperature data also reveals significant deviation from T 3/4 dependence of µ o H c because of dipolar interaction.The amount of heat dissipated E H and µ o H c decrease rapidly with T for D ≈ 8 − 16 nm and λ ≤ 0.6. On the other hand, E H and µ o H c depend weakly on T with D > 16 nm, even in the weak dipolar limit. The present work should provide a better understanding of magnetic hyperthermia to researchers working on this subject. For physicists, it would be interesting to test experimentally the results described in this article.

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Thermal hysteresis of superparamagnetic Gd nanoparticle clusters

Cited by 4 publications

References 22 publications

Nano‐Magnetite Aggregates in Red Soil on Low Magnetic Bedrock, Their Changes During Source‐Sink Transfer, and Implications for Paleoclimate Studies

Nano‐Magnetite Aggregates in Red Soil on Low Magnetic Bedrock, Their Changes During Source‐Sink Transfer, and Implications for Paleoclimate Studies

Reversible Thermal Hysteresis in Heating‐Cooling Cycles of Magnetic Susceptibility: A Fine Particle Effect of Magnetite

Tailoring Heat Dissipation in Ordered Arrays of Dipolar Coupled Magnetic Nanoparticles

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