Bistability of Free Cobalt and Iron Clusters

TL;DR

This study investigates the bistability of magnetic states in cobalt and iron clusters, revealing how their magnetic moments vary between ground and excited states and approach bulk properties as cluster size increases.

Contribution

It demonstrates the existence of bistable magnetic states in CoN and FeN clusters and links their behavior to bulk ferromagnetism, providing new insights into magnetic properties at the nanoscale.

Findings

Bistability observed in magnetic moments of CoN and FeN clusters.

Energy gap between states diminishes with increasing cluster size.

Bulk magnetic behavior involves a superposition of states.

Abstract

The cobalt and iron clusters CoN, FeN (20 < N < 150) measured in a cryogenic molecular beam are found to be bistable with magnetic moments per atom both {\mu}N/N 2{\mu}B in the ground states and {\mu}N */N {\mu}B in the metastable excited states (for iron clusters, {\mu}N ~3N{\mu}B and {\mu}N* N{\mu}B). This energy gap between the two states vanish for large clusters, which explains the rapid convergence of the magnetic moments to the bulk value and suggests that ground state for the bulk involves a superposition of the two, in line with the fluctuating local orders in the bulk itinerant ferromagnetism.