Parity effect in ground state localization of antiferromagnetic chains coupled to a ferromagnet

TL;DR

This study explores how the ground state magnetic configurations of antiferromagnetic chains on a ferromagnetic substrate depend on chain length parity, revealing a transition from classical to quantum behavior due to zero-point energy effects.

Contribution

It demonstrates the parity-dependent ground state behavior in antiferromagnetic chains, combining experimental STM observations with theoretical analysis of zero-point energy effects.

Findings

Ferrimagnetic trimer shows classical collinear ground state

Dimers and tetramers exhibit non-classical states due to zero-point motion

Parity of chain length determines classical or quantum ground state

Abstract

We investigate the ground states of antiferromagnetic Mn nanochains on Ni(110) by spin-polarized scanning tunneling microscopy in combination with theory. While the ferrimagnetic linear trimer experimentally shows the predicted collinear classical ground state, no magnetic contrast was observed for dimers and tetramers where non-collinear structures were expected based on ab-initio theory. This striking observation can be explained by zero-point energy motion for even numbered chains derived within a classical equation of motion leading to non classical ground states. Thus, depending on the parity of the chain length, the system shows a classical or a quantum behavior.