<p>This work investigates a ferrimagnetic Ising nanotube with a spin-3/2 core and a spin-3 shell. The Blume-Capel model and the mean-field approach based on the Gibbs-Bogoliubov inequality are used to examine numerically the hysteresis behavior of this system as a function of various parameters, namely exchange interactions, crystal fields, and temperature. Although the mean-field method, derived from statistical mechanics, neglects fluctuations, it has been successfully applied to describe various phase transition phenomena, particularly hysteresis. This nanotube exhibits first-order phase transitions for low values of magnetic field <i>h</i>, which disappear for higher values. The absolute increase in the crystal field <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="26" /> </InlineMediaObject> <EquationSource Format="TEX">\(D_C\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>C</mi> </msub> </math></EquationSource> </InlineEquation> in the core causes deformation of the hysteresis loops (splitting and lateral broadening) and a significant decrease in remanent magnetization and coercive field, accompanied by the appearance of stability levels. Moreover, increasing the absolute value of <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq2.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">\(D_S\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>S</mi> </msub> </math></EquationSource> </InlineEquation> in the shell transforms the tri-loops into a single loop, and for <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq3.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="68" /> </InlineMediaObject> <EquationSource Format="TEX">\(D_S \le -3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>D</mi> <mi>S</mi> </msub> <mo>≤</mo> <mo>-</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation>, the loop becomes rectangular, displaying a well-defined and stable coercive field. Increasing the exchange interaction <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq4.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="20" /> </InlineMediaObject> <EquationSource Format="TEX">\(J_S\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>J</mi> <mi>S</mi> </msub> </math></EquationSource> </InlineEquation> in the shell leads to more complex loops, evolving from a single loop to multiple loops up to nine. Beyond <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq5.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="62" /> </InlineMediaObject> <EquationSource Format="TEX">\(J_S = 0.4\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>J</mi> <mi>S</mi> </msub> <mo>=</mo> <mn>0.4</mn> </mrow> </math></EquationSource> </InlineEquation>, the system stabilizes with clear tri-loops. Concerning the increase in the absolute value of the interfacial exchange interaction <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq6.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">\(J_{int}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>J</mi> <mrow> <mi mathvariant="italic">int</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>, a single hysteresis loop with weak fluctuations is observed at low <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="41" /> </InlineMediaObject> <EquationSource Format="TEX">\(|J_{int}|\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>J</mi> <mrow> <mi mathvariant="italic">int</mi> </mrow> </msub> <mrow> <mo stretchy="false">|</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, which transforms into multi-loops (three then five), then these loops merge into a broadened loop, with an area that continues to grow by increasing <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="41" /> </InlineMediaObject> <EquationSource Format="TEX">\(|J_{int}|\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>J</mi> <mrow> <mi mathvariant="italic">int</mi> </mrow> </msub> <mrow> <mo stretchy="false">|</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. In addition, the remanent magnetization and coercive field increase with <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="339_2025_8611_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="41" /> </InlineMediaObject> <EquationSource Format="TEX">\(|J_{int}|\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>J</mi> <mrow> <mi mathvariant="italic">int</mi> </mrow> </msub> <mrow> <mo stretchy="false">|</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. Finally, at low temperatures <i>T</i>, the system exhibits tri-loops, however, hysteresis decreases with rising temperature and vanishes beyond the critical temperature. Both remanent magnetization and coercive field gradually decrease with increasing <i>T</i>.</p>

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Hysteresis loops in a mixed-spin (3/2, 3) nanotube with core-shell structure

  • A. El Abbassi,
  • M. Salama,
  • E. B. Choubabi,
  • N. Hachem,
  • M. El Bouziani

摘要

This work investigates a ferrimagnetic Ising nanotube with a spin-3/2 core and a spin-3 shell. The Blume-Capel model and the mean-field approach based on the Gibbs-Bogoliubov inequality are used to examine numerically the hysteresis behavior of this system as a function of various parameters, namely exchange interactions, crystal fields, and temperature. Although the mean-field method, derived from statistical mechanics, neglects fluctuations, it has been successfully applied to describe various phase transition phenomena, particularly hysteresis. This nanotube exhibits first-order phase transitions for low values of magnetic field h, which disappear for higher values. The absolute increase in the crystal field \(D_C\) D C in the core causes deformation of the hysteresis loops (splitting and lateral broadening) and a significant decrease in remanent magnetization and coercive field, accompanied by the appearance of stability levels. Moreover, increasing the absolute value of \(D_S\) D S in the shell transforms the tri-loops into a single loop, and for \(D_S \le -3\) D S - 3 , the loop becomes rectangular, displaying a well-defined and stable coercive field. Increasing the exchange interaction \(J_S\) J S in the shell leads to more complex loops, evolving from a single loop to multiple loops up to nine. Beyond \(J_S = 0.4\) J S = 0.4 , the system stabilizes with clear tri-loops. Concerning the increase in the absolute value of the interfacial exchange interaction \(J_{int}\) J int , a single hysteresis loop with weak fluctuations is observed at low \(|J_{int}|\) | J int | , which transforms into multi-loops (three then five), then these loops merge into a broadened loop, with an area that continues to grow by increasing \(|J_{int}|\) | J int | . In addition, the remanent magnetization and coercive field increase with \(|J_{int}|\) | J int | . Finally, at low temperatures T, the system exhibits tri-loops, however, hysteresis decreases with rising temperature and vanishes beyond the critical temperature. Both remanent magnetization and coercive field gradually decrease with increasing T.