Magnetic Interactions

Peddis, Davide; Jönsson, Petra E.; Laureti, S.; Varvaro, G.

doi:10.1016/b978-0-08-098353-0.00004-x

Cited by 35 publications

(15 citation statements)

References 175 publications

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“…The M DCD (normalized over the M S of each sample) versus reverse magnetic field ( H ) for the corresponding NCs as well as the first-order differentiated curves of M DCD with respect to H (switching field distributions (SFDs)), normalized to ease the comparison, are displayed in Figures b and c, respectively; the latter represents the irreversible component of the susceptibility (χ irr ). This quantity can be viewed as a measure of the energy barrier distribution (which is associated with the distribution of particle’s switching field when we consider nanoparticle-based systems), defined as the field necessary to overcome the energy barrier during an irreversible reversal process. − NC_2 and NC_5 clearly show a single reversal process of magnetization with CFO and SFO phases strongly coupled, with an intermediate H SW value compared to that of the CFO and SFO single phases, thus proving the efficiency of controlling the size and distribution of hard/soft-phase regions thanks to the synthesis method (see Figure S8 for data for all NCs).…”

Section: Resultsmentioning

confidence: 95%

Tuning the Magnetic Properties of Hard–Soft SrFe₁₂O₁₉/CoFe₂O₄ Nanostructures via Composition/Interphase Coupling

et al. 2021

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Magnetic nanocomposites (NCs) are extremely appealing for a wide range of energy-related technological applications, specifically as building blocks for next-generation permanent magnets. The design of such nanostructures requires precise chemical synthesis methods, which will permit the fine-tuning of the magnetic properties. Here we present an in-depth structural, morphological and magnetic characterization of ferrite-based nanostructures obtained through a bottom-up sol−gel approach. The combination of the high coercivity of a hard phase SrFe 12 O 19 (SFO) and the high saturation magnetization of a soft phase, CoFe 2 O 4 (CFO), allowed us to develop exchange-coupled bimagnetic NCs. A symbiotic effect is observed in a SFO/CFO nanocomposite, as the unique oriented growth of SFO prevents grain growth of the CFO, thus restricting the crystallite size of both. Through X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and magnetic measurements we clarify the relationship between the distribution and size of hard/soft particles, the optimization of interfaces and the obtained uniform magnetic response. This study allowed us to establish the potentiality of hard/soft SFO/CFO nanostructures in current permanent magnet technology.

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Section: Resultsmentioning

confidence: 95%

Tuning the Magnetic Properties of Hard–Soft SrFe₁₂O₁₉/CoFe₂O₄ Nanostructures via Composition/Interphase Coupling

et al. 2021

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“…This quantity can be considered to be a measure of the energy barrier distribution which, in a nanoparticle system, is associated to the distribution of particle's switching field, defined as the field necessary to overcome the energy barrier during an irreversible reversal process. 39 In Fig. 7a, we show the switching field distributions (SFDs) of the nanocomposites as obtained from the first order derivatives of the M DCD curves.…”

Section: Magnetization Measurementsmentioning

confidence: 99%

Controlling magnetic coupling in bi-magnetic nanocomposites

et al. 2019

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“…The properties of magnetic nanoparticles are studied through a wide variety of approaches and techniques, among which a central role is played by DC and AC magnetization measurements. Among DC measurements, zerofield-cooled and field-cooled (ZFC/FC) magnetization curves have become an outstanding method of analysis; their presence in experimental papers is nowadays ubiquitous and the existing literature is vast [9][10][11] . As a matter of fact, FC/ZFC curves provide interesting information about a nanoparticle system: in principle, their analysis gives an estimate of the average magnetic moment of nanoparticles 12 , the distribution of nanoparticle sizes 13,14 , the dominant anisotropy energy 15,16 and the presence of interactions 17,18 responsible for ordered or disordered states at low temperatures 19 .…”

Section: Introductionmentioning

confidence: 99%

Linearized rate-equation approach for double-well systems: Cooling- and temperature-dependent low-field magnetization of magnetic nanoparticles

2018

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Low-field magnetization curves for an assembly of polydisperse magnetic nanoparticles described as double-well systems (DWS) with randomly distributed easy axes are generated by means of a rate-equation approach applied to states obtained by cooling with and without a magnetic field. The model has notable advantages over the existing steady-state approaches, allowing one to accurately determine the magnetization frozen in a sample after cooling under field, and to study the effect of the magnitude of the cooling field on the shape of the field-cooled (FC) curve. The DWS scheme keeps validity well above the blocking temperature, making it possible to apply the model over all the region of interest (i.e., when the system is out of equilibrium). A new linearized expression for the magnetization curves is obtained and compared with the existing formulas. It is shown that the new linearized expression for the zero-field-cooled (ZFC) curve is more satisfactory, while no linearized expression for the FC curve is able to accurately reproduce the behavior derived from the rate equations. A new method to obtain the size distribution function is developed; this makes use of the linearized model in the DWS scheme and is based on the analysis of the experimental ZFC curve only. Explicit expressions for the FC/ZFC curves of DWS characterized by an average blocking temperature higher than the starting temperature of the measurement cycle are proposed and shown to naturally explain "anomalous" experimental curves found in the literature.

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Magnetic Interactions

Cited by 35 publications

References 175 publications

Tuning the Magnetic Properties of Hard–Soft SrFe₁₂O₁₉/CoFe₂O₄ Nanostructures via Composition/Interphase Coupling

Tuning the Magnetic Properties of Hard–Soft SrFe₁₂O₁₉/CoFe₂O₄ Nanostructures via Composition/Interphase Coupling

Controlling magnetic coupling in bi-magnetic nanocomposites

Linearized rate-equation approach for double-well systems: Cooling- and temperature-dependent low-field magnetization of magnetic nanoparticles

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Magnetic Interactions

Cited by 35 publications

References 175 publications

Tuning the Magnetic Properties of Hard–Soft SrFe12O19/CoFe2O4 Nanostructures via Composition/Interphase Coupling

Tuning the Magnetic Properties of Hard–Soft SrFe12O19/CoFe2O4 Nanostructures via Composition/Interphase Coupling

Controlling magnetic coupling in bi-magnetic nanocomposites

Linearized rate-equation approach for double-well systems: Cooling- and temperature-dependent low-field magnetization of magnetic nanoparticles

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Tuning the Magnetic Properties of Hard–Soft SrFe₁₂O₁₉/CoFe₂O₄ Nanostructures via Composition/Interphase Coupling

Tuning the Magnetic Properties of Hard–Soft SrFe₁₂O₁₉/CoFe₂O₄ Nanostructures via Composition/Interphase Coupling