Temperature and field direction dependences of first-order reversal curve (FORC) diagrams of hot-deformed Nd-Fe-B magnets

Yomogita, Takahiro; Okamoto, Satoshi; Kikuchi, Nobuaki; Kitakami, Osamu; Sepehri-Amin, H.; Ohkubo, T.; Hono, K.; Akiya, Takahiro; Hioki, K.; Hattori, Atsushi

doi:10.1016/j.jmmm.2017.09.072

Cited by 20 publications

(6 citation statements)

References 32 publications

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“…FORC has been successfully utilized to study an extensive amount of different magnetic systems. Whether for magnetic particles in geologic compounds [4][5][6][7], permanent magnet research [8][9][10], magnetic temperature dependence [11][12][13], the study of nanowires [14][15][16][17][18], or nanostructured dot and antidot systems [19][20][21], first-order reversal curves have a broad range of applications. It has been shown that FORC can also be extended to even more sophisticated methods like second-order reversal curve (SORC) [22], or temperature FORC [23].…”

Section: Introductionmentioning

confidence: 99%

Interpreting first-order reversal curves beyond the Preisach model: An experimental permalloy microarray investigation

et al. 2019

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First-order reversal curves (FORCs) are a powerful tool to separate microscopic coercivities and interactions in a system without the need for lateral resolution. However, measured FORC densities are not always straightforward to interpret, especially if the system is interaction dominated and the Preisach-like interpretation of the FORC density breaks down. This is why FORC is often seen as a magnetic fingerprint instead of a measurement method yielding quantitative information. To understand additional features arising from the interactions in the system, we purposely designed permalloy microstructures which violate the Mayergoyz criteria. These artificial systems allow us to isolate the origin of an additional interaction peak in the FORC density. Modeling the system as a superposition of dipoles allows us to extract interaction strength parameters from this static simulation. Additionally, we suggest a linear relation between integrated interaction peak volume and interaction strength within the system. The presented correlation could be used to investigate the interaction behavior of samples as a function of structural parameters within a series of FORC measurements. This is an important step towards a more quantitative understanding of FORCs which violate the Mayergoyz criteria and away from a fingerprint interpretation.

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Section: Introductionmentioning

confidence: 99%

Interpreting first-order reversal curves beyond the Preisach model: An experimental permalloy microarray investigation

et al. 2019

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“…Besides, all peaks of the two samples were distributed along the H c axis, with weak lines along the H u axis, which suggested that the demagnetization process was mainly dominated by pinning. 18 The pinning centers could be ascribed to the Nd-rich phase. It should be noted that a pinning mechanism in nanostructured magnets has been reported, which is related to domain-wall pinning.…”

Section: Resultsmentioning

confidence: 99%

“…Up to now, the investigations of the magnetic mechanism in such nanostructures have been achieved by Henkel plots, which are able to illustrate the magnetic interactions but cannot characterize details of magnetic switching and magnetic domains. [18][19][20] Fortunately, a new and emerging method, the first-order-reversal-curve (FORC) diagram, can be applied to study the demagnetization process of hysteresis materials, which could provide full mapping of magnetic switching, magnetic interactions, and the magnetic domain nature in the magnetic system. [20][21][22][23][24] The precursors with precise composition were critical to the preparation of Nd 2 Fe 14 B-based nanostructures of the desired compositions.…”

Section: Introductionmentioning

confidence: 99%

First-order-reversal-curve analysis of rare earth permanent magnet nanostructures: insight into the coercivity enhancement mechanism through regulating the Nd-rich phase

Zhu

Wang

et al. 2021

Inorg. Chem. Front.

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“…There we found that the modification causes significant effects on coercivity. With this information on interactions among grains, in Section 7 , we discussed possible extensions of the Preisach model [ 59 , 60 ] to study the effects of interactions on the FORC diagram which provides the characteristics of magnets [ 56 , 57 ].…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The distribution of the coercive fields is related to the FORC by a mathematical formula, and the distribution is called the FORC diagram. The interaction among grains causes changes in the diagram, and the FORC diagram is used to classify the nature of magnets [ 57 ], and it is even used to classify earthenwares in archaeology, because they contain magnetic particles [ 58 ]. To study this effect, extensions of Preisach model have been explored [ 59 , 60 ].…”

Section: Introductionmentioning

confidence: 99%

Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet

Miyashita

Nishino

Toga

et al. 2021

Science and Technology of Advanced Materials

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For the practical use of magnets, particularly at high temperatures, the temperature dependence of magnetic properties is an important ingredient. To study the temperature dependence, methods of treating the thermal fluctuation causing the so-called activation phenomena must be established. To study finite-temperature properties quantitatively, we need atomistic energy information to calculate the canonical distribution. In the present review, we report our recent studies on the thermal properties of the Nd 2 Fe 14 B magnet and the methods of studying them. We first propose an atomistic Hamiltonian and show various thermodynamic properties, e.g., the temperature dependences of the magnetization showing a spin reorientation transition, the magnetic anisotropy energy, the domain wall profiles, the anisotropy of the exchange stiffness constant, and the spectrum of ferromagnetic resonance. The effects of the dipole-dipole interaction (DDI) in large grains are also presented. In addition to these equilibrium properties, we also study coercivity, which is the most important issue for magnets. The temperature dependence of the coercivity of a single grain was studied using the stochastic Landau-Lifshitz-Gilbert equation and also by the analysis of the free energy landscape, which was obtained by Monte Carlo simulation. It was found that the upper limit of coercivity at room temperature is about 3T, which is significantly lower than the so-called theoretical coercivity given by a simple coherent rotation model. The coercivity of a polycrystalline magnet, i.e., an ensemble of grains, is expected to be reduced further by the effects of the grain boundary phase, which is also studied. Surface nucleation is a key ingredient in the domain wall depinning process. Finally, we study the effect of DDI among grains and also discuss the distribution of properties of grains from the viewpoint of first order reversal curve.

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Temperature and field direction dependences of first-order reversal curve (FORC) diagrams of hot-deformed Nd-Fe-B magnets

Cited by 20 publications

References 32 publications

Interpreting first-order reversal curves beyond the Preisach model: An experimental permalloy microarray investigation

Interpreting first-order reversal curves beyond the Preisach model: An experimental permalloy microarray investigation

First-order-reversal-curve analysis of rare earth permanent magnet nanostructures: insight into the coercivity enhancement mechanism through regulating the Nd-rich phase

Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet

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Temperature and field direction dependences of first-order reversal curve (FORC) diagrams of hot-deformed Nd-Fe-B magnets

Cited by 20 publications

References 32 publications

Interpreting first-order reversal curves beyond the Preisach model: An experimental permalloy microarray investigation

Interpreting first-order reversal curves beyond the Preisach model: An experimental permalloy microarray investigation

First-order-reversal-curve analysis of rare earth permanent magnet nanostructures: insight into the coercivity enhancement mechanism through regulating the Nd-rich phase

Atomistic theory of thermally activated magnetization processes in Nd2Fe14B permanent magnet

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Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet