System for ESR measurements at hydrostatic pressures to 60 kilobars

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spectroscopy

Background:

• High-pressure research requires specialized equipment for sample containment and property measurement.
• Electron Spin Resonance (ESR) is a powerful technique for probing material properties under extreme conditions.

Purpose of the Study:

• To develop and validate a novel Bridgman-anvil pressure cell utilizing single-crystal sapphire.
• To demonstrate the capability of this system for high-pressure ESR measurements on ruby (Cr(3+)).

Main Methods:

• A single-crystal sapphire acts as both a microwave cavity and an anvil in a Bridgman-anvil geometry.
• Hydrostatic pressures are applied using a metal gasket, and pressure is measured via ruby fluorescence.
• Electron Spin Resonance (ESR) spectroscopy is employed to collect data.

Main Results:

• The system allows for purely hydrostatic pressures up to 60 kilobars with minimal data degradation.
• Precise measurements of the pressure dependence of zero-field splitting (delta) in ruby were obtained.
• The first and second derivatives of delta with respect to pressure were determined: ddelta/dP = (6.70±0.08) x 10⁻⁴ cm⁻¹/kbar and d²delta/dP² = (-2.44±0.30) x 10⁻⁶ cm⁻¹/kbar² at P=0.
• The fractional change in the gyromagnetic ratio g(11) was found to be less than 2 x 10⁻⁴ up to 60 kilobars.

Conclusions:

• The sapphire Bridgman-anvil cell is a viable and precise tool for high-pressure ESR studies.
• The technique provides high-quality data, enabling detailed analysis of material properties under pressure.
• This method opens new avenues for investigating phase transitions and electronic structures in materials at extreme pressures.