# Br-Mediated Spin-State Control in Nickelocene and Cobaltocene

## TL;DR

This paper shows how bromine atoms can control the spin states of nickelocene and cobaltocene molecules, which could help in developing advanced electronic devices.

## Contribution

The study introduces a novel method of using bromine atoms to manipulate molecular spin states for spintronic applications.

## Key findings

- Br atoms can induce a spin-state transition in NiCp2 from S = 1 to S = 1/2 and further to S = 0.
- Hybridization with Br atoms completely quenches the spin moment in CoCp2.
- This approach offers a scalable strategy for designing molecular spintronic devices.

## Abstract

Single-molecule magnets
represent promising materials due to their
stable magnetic states and long relaxation times. Precise engineering
of their quantum properties is of importance to realize advanced electronic
devices, such as high-density data storage, quantum computing, and
spintronics. Here, we investigate the spin state of nickelocene (NiCp2) and cobaltocene (CoCp2) molecules manipulated
by Br atoms. With a combination of scanning tunneling microscopy and
density functional theory calculations, we reveal that the high electronegativity
of Br atoms significantly changes the magnetic properties of both
NiCp2 and CoCp2. For NiCp2, the spin-state
transition from its intrinsic S = 1 to S = 1/2 occurs when the Br atoms underlying the molecule consist of
more than five atoms. The spin state is further shifted to S = 0 by approaching a Br-terminated tip toward the molecule.
In contrast, a strong hybridization between CoCp2 and Br
atoms leads to a complete quenching of its spin moment. This strategy
for tuning molecular spin states provides a promising route toward
the scalable design of molecular spintronic devices.