Calculated properties of GdNi intermetallic compound for the nitrogen liquefaction process: insight into <i>ab-initio</i> computations and Monte Carlo simulation

Abstract

Abstract Theoretical study on the ground state proprieties of GdNi intermetallic compound and its magnetic observable curves, as well as its magneto-caloric effect (MCE) was performed. It was established that the magnetic moment of Gd atom is found to be 7.11 μ B and the exchange coupling parameters are found to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>J</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>3.7</mml:mn> </mml:math> meV and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>J</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>2.06</mml:mn> </mml:math> meV. Moreover, in good agreement with a recent experimental work, the magnetization, magnetization derivative and susceptibility curves confirmed that the studied sample undergoes a ferromagnetic ordering at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> </mml:math> = 70 K. Further, it was found that MCE in regard to the peak value of magnetic entropy ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>−</mml:mo> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:msub> <mml:mrow> <mml:mi>S</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">mag</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mfenced close=")" open="(" separators=""> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> </mml:math> ) around <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>,</mml:mo> </mml:math> can be enhanced with high magnetic fields. Besides, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>−</mml:mo> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:msubsup> <mml:mrow> <mml:mi>S</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">mag</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">Max</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> (the maximum value of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>−</mml:mo> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:msub> <mml:mrow> <mml:mi>S</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">mag</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mfenced close=")" open="(" separators=""> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> </mml:math> ) and RCP (Relative Cooling Power) attain maximum values of 17,13 JKg −1 K −1 and 549 JKg −1 close to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>,</mml:mo> </mml:math> respectively for external magnetic field of 5T, being in good agreement with the experimental ones. The present findings enable us to say that GdNi-based magnetic refrigeration can be considered as a promising technology for the nitrogen liquefaction process.