On the magnetic bistability of small iron clusters used in scanning tunneling microscopy tip preparation

November 21, 2023

Jisoo Yu, Corina Urdaniz, Young Namgoong, and Christoph Wolf

New Journal of Physics, Volume 25


Here, we studied the magnetic bistability of small iron cluster which is crucial for ESR-active tip. Based on DFT calculation, the less symmetric structures are more likely to exhibit higher magnetic bistabilities.


The combination of electron spin resonance with scanning tunneling microscopy has resulted in a unique surface probe with sub-nm spatial and neV energy resolution. The preparation of a stable magnetic microtip is of central importance, yet, at the same time remains one of the hardest tasks. In this work, we rationalize why creating such microtips by picking up a few iron atoms often results in magnetically stable probes with two distinct magnetic states. By using density functional theory, we show that randomly formed clusters of five iron atoms can exhibit this behavior with magnetic anisotropy barriers of up to 73 meV. We explore the dependence of the magnetic behavior of such clusters on the geometrical arrangement and find a strong correlation between magnetic and geometric anisotropy—the less regular the cluster the higher its magnetic anisotropy barrier. Finally, our work rationalizes the experimental strategy of obtaining stable magnetic microtips.