# A nano-carbon route to rare earth free permanent magnetism

## TL;DR

This paper introduces a novel nano-carbon based magnetic material with enhanced coercivity, offering a rare-earth free alternative for permanent magnets crucial in renewable energy and electronics.

## Contribution

It presents a hybrid cobalt and C60 molecule bilayer exhibiting new magnetic anisotropy called pi-anisotropy, not explained by existing models.

## Key findings

- Significant coercivity enhancement with minimal magnetization loss.
- Identification of a new anisotropy mechanism called pi-anisotropy.
- Potential for room-temperature, carbon-based hard magnetic films.

## Abstract

High coercivity magnets are an important resource for renewable energy, electric vehicles and memory technologies. Most hard magnetic materials incorporate rare-earths such as neodymium and samarium, but the concerns about the environmental impact and supply stability of these materials is prompting research into alternatives. Here, we present a hybrid bilayer of cobalt and the nano-carbon molecule C60 which exhibits significantly enhanced coercivity with minimal reduction in magnetisation. We demonstrate how this anisotropy enhancing effect cannot be described by existing models of molecule-metal magnetic interfaces. We outline a new form of magnetic anisotropy, arising from asymmetric magneto-electric coupling in the metal-molecule interface. Because this phenomenon arises from pi-d hybrid orbitals, we propose calling this effect pi-anisotropy. While the critical temperature of this effect is currently limited by the rotational degree of freedom of the chosen molecule, C60, we describe how surface functionalisation would allow for the design of room-temperature, carbon based hard magnetic films.