Research Description

AC Magnetic Susceptibility Properties of Nanoparticles

In the physics of finite size effects, nanoparticles present a unique arena; between molecular and microscopic length scales, where bulk properties of a material may change according to the size of the particle. Nanoparticles have found applications in electronic and biological industries, and have the potential to fill gaps in theories of magnetism on the quantum level.

In an effort to characterize the properties of nanoparticles of various sizes and chemical compositions, ac (alternating current) magnetic susceptibility measurements are being made using a custom-made probe. The experimental apparatus incorporates mutual inductance coils suspended in the cooling chamber of a commercial SQUID (Superconducting Quantum Interference Device) magnetometer, with phase sensitive responses to ac excitation signals being made with a lock-in amplifier, thereby allowing the temperature (from 2K to 300K) and frequency (from 1mHz to 1MHz) dependencies of magnetization to be determined. Early generations of the probe have produced promising results in measurements of superconducting transitions and spin crossover phenomena. The current version has the added feature of an optical fiber, enabling studies of the effects of photoexcitation. The range of functionalities provided by the probe will make significant contributions to the understanding of the behavior of novel magnetic materials in the nanoscale regime.