An ultra-low field SQUID magnetometer for measuring antiferromagnetic and weakly remanent magnetic materials at low temperatures

TL;DR

This paper introduces a highly sensitive, ultra-low field SQUID magnetometer capable of measuring weak magnetic signals in antiferromagnetic and remanent magnetic materials at low temperatures, enabling new research opportunities.

Contribution

The paper presents a novel SQUID magnetometer setup with ultra-low magnetic background and temperature control, optimized for studying weakly magnetic materials.

Findings

Achieved a magnetic field resolution of approximately 10 fT.

Successfully measured weak magnetic signals in antiferromagnetic materials.

Enabled studies of spin-spiral multiferroics, skyrmion materials, and spin ices.

Abstract

A novel setup for the measurement of magnetic fields external to certain antiferromagnets and generally weakly remanent magnetic materials is presented. The setup features a highly sensitive Super Conducting Quantum Interference Device (SQUID) magnetometer with a magnetic field resolution of approx. 10 fT, non-electric thermalization of the sample space for a temperature range of 1.5 - 65 K with a non-electric sample movement drive and optical position encoding. To minimize magnetic susceptibility effects, the setup components are degaussed and realized with plastic materials in sample proximity. Running the setup in magnetically shielded rooms allows for a well-defined ultra low magnetic background field well below 150 nT in situ. The setup enables studies of inherently weak magnetic materials which cannot be measured with high field susceptibility setups, optical methods or neutron scattering techniques, giving new opportunities for the research on e.g. spin-spiral multiferroics, skyrmion materials and spin ices.