Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Engineering the Magnetocaloric Effect in Nd$T_4$B

Kyle W. Fruhling, Enrique O. González Delgado, Siddharth Nandanwar, Xiaohan Yao, Zafer Turgut, Michael A. Susner, Fazel Tafti

TL;DR

This work investigates magnetocaloric effect (MCE) engineering in the Nd$T_4B$ family (T = Fe, Co, Ni), exploiting tunable Curie temperatures and magnetic moments in a kagome-based lattice. By synthesizing seven representative Nd$T_4B$ compositions, constructing ternary phase diagrams, and applying a linear interpolation, the authors design NdFe$_{1.15}$Co$_{0.46}$Ni$_{2.39}$B, which exhibits a broad MCE centered near room temperature with a large RC of approximately $250$ J kg$^{-1}$ at $H_{ ext{max}}=5$ T, despite a modest peak entropy change $- ext{Δ}S_{ ext{MAX}}\, ext{≈}\,0.68$ J kg$^{-1}$ K$^{-1}$. They also observe a two-peak MCE in several mixed-metal compositions, enabling potential multi-stage cooling with comparable RC across stages. Overall, the study demonstrates that compositionally engineering a tunable Nd-based boride platform can achieve wide-range, high-capacity MCE suitable for practical magnetic refrigeration and motivates scalable, diagram-guided discovery for other material families.

Abstract

We present a comprehensive study of the magnetocaloric effect (MCE) in the Nd$T_4$B system where $T$ = Fe, Co, and Ni. These compounds are ferromagnetic kagome materials with tunable ordering temperatures, transition width, and magnetic moments depending on the choice of transition metal. Thus, they are good candidates for investigating the MCE. We characterize the MCE using standard metrics and construct ternary phase diagrams as functions of Fe, Co, and Ni concentrations. Using these phase diagrams, we engineer the composition NdFe$_{1.15}$Co$_{0.46}$Ni$_{2.39}$B to maximize the MCE. Interestingly, the Nd$T_4$B system shows a notable entropy change over a wide temperature range ($\sim$10 to 650 K), and particular compositions have notable MCEs spanning hundreds of Kelvin, making this a suitable system to study for technologies used in a wide range of temperatures. In a few cases, we observe a two-peak MCE. These two transitions, releasing comparable entropy, provide an interesting platform to study for applications in multi-stage cooling.

Engineering the Magnetocaloric Effect in Nd$T_4$B

TL;DR

This work investigates magnetocaloric effect (MCE) engineering in the Nd family (T = Fe, Co, Ni), exploiting tunable Curie temperatures and magnetic moments in a kagome-based lattice. By synthesizing seven representative Nd compositions, constructing ternary phase diagrams, and applying a linear interpolation, the authors design NdFeCoNiB, which exhibits a broad MCE centered near room temperature with a large RC of approximately J kg at T, despite a modest peak entropy change J kg K. They also observe a two-peak MCE in several mixed-metal compositions, enabling potential multi-stage cooling with comparable RC across stages. Overall, the study demonstrates that compositionally engineering a tunable Nd-based boride platform can achieve wide-range, high-capacity MCE suitable for practical magnetic refrigeration and motivates scalable, diagram-guided discovery for other material families.

Abstract

We present a comprehensive study of the magnetocaloric effect (MCE) in the NdB system where = Fe, Co, and Ni. These compounds are ferromagnetic kagome materials with tunable ordering temperatures, transition width, and magnetic moments depending on the choice of transition metal. Thus, they are good candidates for investigating the MCE. We characterize the MCE using standard metrics and construct ternary phase diagrams as functions of Fe, Co, and Ni concentrations. Using these phase diagrams, we engineer the composition NdFeCoNiB to maximize the MCE. Interestingly, the NdB system shows a notable entropy change over a wide temperature range (10 to 650 K), and particular compositions have notable MCEs spanning hundreds of Kelvin, making this a suitable system to study for technologies used in a wide range of temperatures. In a few cases, we observe a two-peak MCE. These two transitions, releasing comparable entropy, provide an interesting platform to study for applications in multi-stage cooling.

Paper Structure

This paper contains 11 sections, 5 equations, 3 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Experimental Methods
  3. Material Synthesis
  4. Structural and Chemical Characterizations
  5. Magnetic Characterization
  6. Results and Discussion
  7. MCE Metrics
  8. MCE in NdT4B Family
  9. Engineered Material
  10. Two Stage Cooling Behavior
  11. Conclusions

Figures (3)

  • Figure 1: (a) Crystal structure of NdNi4B illustrated by VESTAmomma_vesta_2011kuzma_x-ray_1983. (b) Magnetization of NdNi4B showing the FM transition at $T_\text{C}=13$ K. Inset: a button of NdNi4B produced by arc-melting. (c) Several magnetization curves obtained near the transition temperature. (d) Change in the magnetic entropy ($-\Delta S_m$) and refrigerant capacity ($RC$) of NdNi4B near $T_\text{C}$.
  • Figure 2: For various transition metal ratios, the color plots show the change in (a) temperature of the peak in $-\Delta S_m$, (b) the maximum change in the magnetic entropy at 5 T, and (c) the refrigerant capacity at 5 T. On all plots, the dashed white line represents a peak in $-\Delta S_m$ at 300 K.
  • Figure 3: Top: characterizing the MCE in NdFe_1.15Co_0.46Ni_2.39B. (a) Magnetization as a function of temperature showing the FM transition. (b) Magnetization isotherms over a wide temperature range. (c) $-\Delta S_m$ over the wide FM transition. Bottom: characterizing the MCE in NdCo3NiB. (d) Two FM transitions in NdCo3NiB. (e) Magnetic isotherms over a wide temperature range. Two regions of increased separation between neighboring isotherms can be seen around 220 K and 360 K. (f) A two-peak behavior in $-\Delta S_m$ fitted to the sum of two Voigt functions centered around 230 K and 356 K.