Entrapment of magnetic micro-crystals for on-chip electron spin resonance studies

TL;DR

This paper introduces a method to precisely position magnetic micro-crystals on-chip for electron spin resonance studies, enabling high-sensitivity measurements at low temperatures with potential applications in quantum sensing.

Contribution

A novel technique for trapping micro-crystals containing spins at specific locations on a substrate for on-chip ESR measurements.

Findings

Successful entrapment of micro-crystals for ESR

Performed ESR on mesoscopic crystals at 34 GHz

Demonstrated measurement of diluted Cr$^{5+}$ spins near sensitivity limits

Abstract

On-chip Electron Spin Resonance (ESR) of magnetic molecules requires the ability to precisely position nanosized samples in antinodes of the electro-magnetic field for maximal magnetic interaction. A method is developed to entrap micro-crystals containing spins in a well defined location on a substrate's surface. Traditional cavity ESR measurements are then performed on a mesoscopic crystal at 34 GHz. Polycrystalline diluted Cr$^{5+}$ spins were entrapped as well and measured while approaching the lower limit of the ESR sensitivity. This method suggests the feasibility of on-chip ESR measurements at dilution refrigerator temperatures by enabling the positioning of samples atop an on-chip superconducting cavity.