Executive Summary : | Nano-particle magnetism offers fascinating physics and applications, with micro-SQUID magnetometery providing a clearer picture of its intrisic magnetism compared to bulk probes. This project aims to optimize micro-SQUIDs to improve sensitivity and bandwidth, and investigate different magnetic nano-particles. The team plans to investigate the time scale of non-equilibrium due to phase-slip events in superconducting weak-links using small AC modulation over a wide frequency range. The project also aims to set up a high-quality niobium film deposition setup at IIT Kanpur, enabling the fabrication of niobium weak-link devices and micro-SQUIDs. This will help investigate other device geometries and configurations for further optimization and new ideas. The team is currently working on the magnetism of single ferromagnetic particles of about 100nm size, specifically the magnetization reversal in non-single domain ferromagnetic nano-particles. The magnetization reversal is a complex phenomenon involving non-linearities arising from long-range dipolar and local exchange interactions with crystalline anisotropies. Recent measurements on single ferrite nano-particles show switching time distributions close to switching fields, implying a complex energy landscape for vortex motion. The ongoing testing of the low temperature SQUID amplifier with micro-SQUIDs is expected to improve micro-SQUID performance. The team plans to take up non-ferromagnetic nano-particles, such as those with antiferromagnetic or spin disordered nature in bulk, after achieving a sensitivity below 100 times that of a single electron. This will help understand the behavior of uncompensated surface spins and the effect of surface in spin frustrated magnetic systems in nano-particle form. |