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Energy-Dependent Magnetic Modifications in HOPG via Microbeam Scanning

Ram Kumar, Aditya H. Kelkar, Neeraj Shukla, Paras Poswal, Sheshmani Singh

TL;DR

The paper investigates how ion-beam energy governs defect-induced magnetism in carbon-based materials, focusing on highly oriented pyrolytic graphite (HOPG). It employs microbeam irradiation with carbon ions ($0.6-1.2$ MeV) and protons ($1-3$ MeV) at a fixed fluence, supplemented by SRIM defect modeling and PIXE impurity analysis, with magnetization characterized by VSM. The results show a strong dependence on both ion species and energy, with a maximum carbon-induced magnetization at $1.2$ MeV and higher magnetization for protons at $3$ MeV under the same dose; carbon also generates more lattice defects than protons, and impurity magnetism is ruled out by PIXE. These findings demonstrate that energy-tuned ion irradiation can pattern localized ferromagnetic order in carbon-based materials, offering a pathway for lightweight magnets and spintronic/memory applications at the nanoscale.

Abstract

Medium-energy ion irradiation is a promising technique for inducing magnetism in materials with partially filled d or f electron bands. This approach enables precise control over the density and spatial distribution of irradiation-induced defects, which play a crucial role in modifying the electronic and magnetic properties of the system. The primary objective of this experiment was to investigate the influence of ion energy variation on the magnetic properties of highly oriented pyrolytic graphite (HOPG). To achieve this, HOPG samples were irradiated with protons 1-3 MeV and carbon ions 600 keV - 2 MeV. A significant change in the magnetic moment was observed with respect to the irradiation energy for both ion species. The effect of energy variation was analyzed using a vibrating sample magnetometer (VSM) and SRIM simulations. The results demonstrate that ion-beam-induced magnetic ordering strongly depends on both the ion species and the beam energy. Magnetic measurements were performed with varying irradiation energies, showing that carbon ion irradiation produces a higher degree of magnetic ordering compared to proton irradiation at the same dose. The maximum magnetization was obtained at 1.2 MeV carbon ion irradiation. SRIM simulations confirm that carbon ions create a greater number of lattice defects than proton ions, which correlates with the enhanced magnetic response.

Energy-Dependent Magnetic Modifications in HOPG via Microbeam Scanning

TL;DR

The paper investigates how ion-beam energy governs defect-induced magnetism in carbon-based materials, focusing on highly oriented pyrolytic graphite (HOPG). It employs microbeam irradiation with carbon ions ( MeV) and protons ( MeV) at a fixed fluence, supplemented by SRIM defect modeling and PIXE impurity analysis, with magnetization characterized by VSM. The results show a strong dependence on both ion species and energy, with a maximum carbon-induced magnetization at MeV and higher magnetization for protons at MeV under the same dose; carbon also generates more lattice defects than protons, and impurity magnetism is ruled out by PIXE. These findings demonstrate that energy-tuned ion irradiation can pattern localized ferromagnetic order in carbon-based materials, offering a pathway for lightweight magnets and spintronic/memory applications at the nanoscale.

Abstract

Medium-energy ion irradiation is a promising technique for inducing magnetism in materials with partially filled d or f electron bands. This approach enables precise control over the density and spatial distribution of irradiation-induced defects, which play a crucial role in modifying the electronic and magnetic properties of the system. The primary objective of this experiment was to investigate the influence of ion energy variation on the magnetic properties of highly oriented pyrolytic graphite (HOPG). To achieve this, HOPG samples were irradiated with protons 1-3 MeV and carbon ions 600 keV - 2 MeV. A significant change in the magnetic moment was observed with respect to the irradiation energy for both ion species. The effect of energy variation was analyzed using a vibrating sample magnetometer (VSM) and SRIM simulations. The results demonstrate that ion-beam-induced magnetic ordering strongly depends on both the ion species and the beam energy. Magnetic measurements were performed with varying irradiation energies, showing that carbon ion irradiation produces a higher degree of magnetic ordering compared to proton irradiation at the same dose. The maximum magnetization was obtained at 1.2 MeV carbon ion irradiation. SRIM simulations confirm that carbon ions create a greater number of lattice defects than proton ions, which correlates with the enhanced magnetic response.

Paper Structure

This paper contains 9 sections, 3 figures, 2 tables.

Table of Contents

  1. Introduction:-
  2. Sample Preparation and microbeam scanning
  3. Results
  4. Magnetization studies of unirradiated and microbeam irradiated HOPG samples
  5. Estimated Defect Density, Penetration Depth, and Energy Dissipation of Ions in HOPG (via SRIM)
  6. Impurity Analysis by PIXE (Particle Induced X-ray Emission)
  7. Discussion
  8. Conclusions
  9. Acknowledgments

Figures (3)

  • Figure 1: Magnetization response of carbon ion beam irradiated samples at same dose ($100~\text{pC}/\mu\text{m}^2$) with energy variation from 2-0.6 MV .
  • Figure 2: Magnetization response of proton ion beam irradiated samples at same dose ($100~\text{pC}/\mu\text{m}^2$) with energy variation from 3-1 MV .
  • Figure 3: Particle Induced X-ray Emission (PIXE) data illustrating Fe $K_{\alpha}$ and $K_{\beta}$ peaks in virgin and carbon-ion-irradiated HOPG samples. .