Resonant torsion magnetometry in anisotropic quantum materials

Area of Science:

• Condensed Matter Physics
• Quantum Materials Science

Background:

• Quantum materials exhibit unusual behaviors due to low-dimensional physics and anisotropy in spin and charge.
• Understanding magnetic anisotropy is crucial for characterizing these materials.

Purpose of the Study:

• Introduce a novel method to quantify magnetic anisotropy.
• Demonstrate the method's sensitivity and applicability to nanoscale samples.

Main Methods:

• Define and measure the magnetotropic coefficient (∂²F/∂θ²) using atomic force microscopy (AFM).
• Utilize shifts in AFM cantilever resonant frequency under magnetic field for detection.
• Achieve part per 100 million sensitivity.

Main Results:

• Successfully measured magnetic anisotropy in the Weyl semimetal NbP using nanogram-scale samples.
• Demonstrated the sensitivity of the magnetotropic coefficient to anisotropic phase transitions in the spin-liquid candidate RuCl₃.
• Enabled quantitative comparison with thermodynamic coefficients via Ehrenfest relations.

Conclusions:

• The developed AFM-based method provides a highly sensitive tool for measuring magnetic anisotropy in quantum materials.
• This technique is applicable to small-scale samples and sensitive to phase transitions.
• Offers a new pathway for characterizing exotic magnetic phenomena.