Room-temperature ferromagnetism in graphitic petal arrays

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Exploring novel ferromagnetic materials is crucial for advancing spintronic devices.
• Graphitic nanostructures offer unique electronic and magnetic properties.
• Catalyst-free growth methods are desirable for material purity and simplified fabrication.

Purpose of the Study:

• To investigate the potential for room-temperature ferromagnetism in catalyst-free graphitic petal arrays.
• To characterize the magnetic properties and understand the origin of ferromagnetism.
• To assess the impact of post-growth annealing on magnetic behavior.

Main Methods:

• Growth of graphitic petal arrays on silicon substrates using microwave plasma chemical vapor deposition (MPCVD) without a catalyst.
• Characterization using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) to verify material composition and rule out impurities.
• Magnetic property measurements, including hysteresis loops, at room temperature (300 K).
• Post-growth annealing in an oxygen (O2) atmosphere.

Main Results:

• Successful synthesis of graphitic petal arrays exhibiting ferromagnetism at room temperature.
• Absence of ferromagnetic impurities confirmed by Raman and XPS.
• Observed saturation magnetization of ~4.67 emu cm⁻³ and coercivity of ~105 Oe at 300 K.
• Oxygen annealing reduced saturation magnetization to ~2.1 emu cm⁻³ and coercivity to ~75 Oe.

Conclusions:

• Graphitic petal arrays grown without a catalyst demonstrate intrinsic room-temperature ferromagnetism.
• Ferromagnetism is likely attributed to edge defects and vacancies within the graphitic petals.
• Oxygen annealing can modulate the magnetic properties, suggesting defect-related magnetism.