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<p>We used density functional theory and Monte Carlo simulations to look into the magnetic, electronic, and magnetocaloric (MC) properties of a half-metallic Co<sub>2</sub>NbAl Heusler alloy. Phonon calculations confirmed its dynamical stability. Antisite disorder induced a half-metallic ground state, with a 0.62&#xa0;eV bandgap in the minority spin channel and metallic behaviour in the majority spin channel. The magnetism primarily originates from Co atoms (1.10&#xa0;μ<sub>B</sub>), with a minor induced moment on Nb atoms (0.06&#xa0;μ<sub>B</sub>), while Al remains non-magnetic, resulting in a total moment of 2.03&#xa0;μ<sub>B</sub>/f.u. This value exceeds the experimentally reported 1.35 μ<sub>B</sub>, likely due to A2-type antisite disorder. Monte Carlo simulations estimated the Curie temperature (<i>T</i><sub>C</sub>) at 348&#xa0;K, closely matching the experimental value of 383&#xa0;K, while the mean-field approximation significantly overestimated it at 541.8&#xa0;K. The relative cooling power (RCP), derived from isothermal magnetic entropy changes, was 11.9&#xa0;J&#xa0;kg<sup>−1</sup> at 0–1&#xa0;T and 114.6&#xa0;J&#xa0;kg<sup>−1</sup> at 0–9&#xa0;T magnetic field changes, respectively. Co<sub>2</sub>NbAl retained its half-metallicity under pressures up to 10&#xa0;GPa. Beyond 2&#xa0;GPa, the magnetic moment and magnetic exchange interaction strengths declined significantly, while the energy gap steadily decreased. The magnetic entropy change (–Δ<i>S</i><sub>m</sub>) increased, <i>T</i><sub>C</sub> decreased, and RCP increased nonlinearly. This showed that Co<sub>2</sub>NbAl has a pressure-sensitive MC response.</p>

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Study of the Magnetic, Electronic and Magnetocaloric Properties of Half-Metallic Co2NbAl Using First-Principles and Monte Carlo Simulations

  • 期刊论文

  • 发表日期：

    2025年12月11日

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  • Karumuri Venkanna,
  • C. H. Prashanth,
  • Abhijit Nayak,
  • P. Rambabu,
  • Bheema Lingam Chittari,
  • Krishnamurthy Jyothinagaram

摘要

We used density functional theory and Monte Carlo simulations to look into the magnetic, electronic, and magnetocaloric (MC) properties of a half-metallic Co2NbAl Heusler alloy. Phonon calculations confirmed its dynamical stability. Antisite disorder induced a half-metallic ground state, with a 0.62 eV bandgap in the minority spin channel and metallic behaviour in the majority spin channel. The magnetism primarily originates from Co atoms (1.10 μB), with a minor induced moment on Nb atoms (0.06 μB), while Al remains non-magnetic, resulting in a total moment of 2.03 μB/f.u. This value exceeds the experimentally reported 1.35 μB, likely due to A2-type antisite disorder. Monte Carlo simulations estimated the Curie temperature (TC) at 348 K, closely matching the experimental value of 383 K, while the mean-field approximation significantly overestimated it at 541.8 K. The relative cooling power (RCP), derived from isothermal magnetic entropy changes, was 11.9 J kg−1 at 0–1 T and 114.6 J kg−1 at 0–9 T magnetic field changes, respectively. Co2NbAl retained its half-metallicity under pressures up to 10 GPa. Beyond 2 GPa, the magnetic moment and magnetic exchange interaction strengths declined significantly, while the energy gap steadily decreased. The magnetic entropy change (–ΔSm) increased, TC decreased, and RCP increased nonlinearly. This showed that Co2NbAl has a pressure-sensitive MC response.