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<p>The magnetocaloric effect (MCE) in novel rare-earth-free compounds near room temperature is currently of paramount interest for magnetic cooling applications. To support this effort, an analytical model is essential for predicting key magnetocaloric properties—namely, magnetic entropy change (ΔS), heat capacity change (ΔCₚ), and relative cooling power (RCP)—to accelerate ongoing materials research. However, existing models based on temperature-dependent magnetization behavior are typically limited to single magnetic transitions and their distributions. To address this limitation, we introduce a double sigmoidal function (DSF) capable of capturing multiple magnetic transitions while offering a stronger physical foundation. As a case study, we selected ordered D0₃-phase Fe₃Al alloys (27 ≤ Al ≤ 31 at%) synthesized by Shull et al. and used them to simulate MCE properties under small magnetic fields (<i>H</i>). Notably, a maximum entropy change of ΔSₘₐₓ = − 0.14&#xa0;mJ/kg·K and a variation in Δ<i>C</i>ₚ from − 0.09 to + 0.17&#xa0;mJ/kg·K were predicted at <i>H</i> = 50 Oe near the Curie temperature (438&#xa0;K) for Fe₃Al with 30 at% Al. Our model identifies various magnetic transitions—such as ferromagnetic (FM) to superparamagnetic (SPM), and FM/SPM to mictomagnetic (Micto)—and characterizes their nature using parameters <i>p</i> (weight factor) and <i>h</i> (inverse of transition width), both of which vary with Al concentration. The model also successfully characterizes the unique crossover from normal to inverse MCE in Fe₃Al alloys, suggesting its potential as a computational tool for the intelligent design of new magnetocaloric materials for on-chip cooling devices. While the model is particularly effective at low magnetic fields and near magnetic transitions, it remains straightforward and requires fewer thermomagnetic parameters compared to many existing models.</p>

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Comprehensive modeling of magnetocaloric effects in Fe-Al alloys across magnetic transitions

  • 期刊论文

  • 发表日期：

    2025年6月13日

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  • Murtaza Bohra,
  • Siddharth Pardeshi,
  • Anil Annadi,
  • Vidyadhar Singh,
  • Raúl López-Martín,
  • Evropi Toulkeridou,
  • Panagiotis Grammatikopoulos

摘要

The magnetocaloric effect (MCE) in novel rare-earth-free compounds near room temperature is currently of paramount interest for magnetic cooling applications. To support this effort, an analytical model is essential for predicting key magnetocaloric properties—namely, magnetic entropy change (ΔS), heat capacity change (ΔCₚ), and relative cooling power (RCP)—to accelerate ongoing materials research. However, existing models based on temperature-dependent magnetization behavior are typically limited to single magnetic transitions and their distributions. To address this limitation, we introduce a double sigmoidal function (DSF) capable of capturing multiple magnetic transitions while offering a stronger physical foundation. As a case study, we selected ordered D0₃-phase Fe₃Al alloys (27 ≤ Al ≤ 31 at%) synthesized by Shull et al. and used them to simulate MCE properties under small magnetic fields (H). Notably, a maximum entropy change of ΔSₘₐₓ = − 0.14 mJ/kg·K and a variation in ΔCₚ from − 0.09 to + 0.17 mJ/kg·K were predicted at H = 50 Oe near the Curie temperature (438 K) for Fe₃Al with 30 at% Al. Our model identifies various magnetic transitions—such as ferromagnetic (FM) to superparamagnetic (SPM), and FM/SPM to mictomagnetic (Micto)—and characterizes their nature using parameters p (weight factor) and h (inverse of transition width), both of which vary with Al concentration. The model also successfully characterizes the unique crossover from normal to inverse MCE in Fe₃Al alloys, suggesting its potential as a computational tool for the intelligent design of new magnetocaloric materials for on-chip cooling devices. While the model is particularly effective at low magnetic fields and near magnetic transitions, it remains straightforward and requires fewer thermomagnetic parameters compared to many existing models.