Atomic-scale spin-polarization maps using functionalized superconducting probes

TL;DR

This paper introduces a new method using functionalized superconducting STM tips with magnetic impurities to quantitatively map atomic-scale spin-polarization in samples, achieving high sensitivity and absolute measurement capability.

Contribution

The study develops a novel superconducting STM tip functionalization technique with impurity states, enabling absolute and highly sensitive atomic-scale spin-polarization mapping.

Findings

Achieved quantitative measurement of sample spin-polarization.

Demonstrated high spin-sensitivity with impurity-functionalized tips.

Validated method by comparing with traditional spin-polarized STM results.

Abstract

A scanning tunneling microscope (STM) with a magnetic tip that has a sufficiently strong spin-polarization can be used to map the sample's spin structure down to the atomic scale but usually lacks the possibility to absolutely determine the value of the sample's spin-polarization. Magnetic impurities in superconducting materials give rise to pairs of perfectly, i.e. 100% spin-polarized sub-gap resonances. In this work, we functionalize the apex of a superconducting Nb STM-tip with such impurity states by attaching Fe atoms to probe the spin-polarization of atom-manipulated Mn nanomagnets on a Nb(110) surface. By comparison with spin-polarized STM measurements of the same nanomagnets using Cr bulk tips we demonstrate an extraordinary spin-sensitivity and the possibility to measure the sample's spin-polarization values quantitatively with our new functionalized probes.