# Ultrathin ferrite nanosheets for room-temperature two-dimensional magnetic semiconductors

## TL;DR

Researchers created stable, ultrathin cobalt ferrite nanosheets with magnetic properties that work above room temperature, opening new possibilities for spintronic devices.

## Contribution

A new method to synthesize air-stable, semiconducting cobalt ferrite nanosheets with thickness down to one unit cell and high Curie temperature.

## Key findings

- Cobalt ferrite nanosheets exhibit hard magnetic behavior and high Curie temperature above 390 K.
- The nanosheets show strong dimensionality effects and are stable at room temperature.
- The material's properties make it suitable for computing, sensing, and information storage applications.

## Abstract

The discovery of magnetism in ultrathin crystals opens up opportunities to explore new physics and to develop next-generation spintronic devices. Nevertheless, two-dimensional magnetic semiconductors with Curie temperatures higher than room temperature have rarely been reported. Ferrites with strongly correlated d-orbital electrons may be alternative candidates offering two-dimensional high-temperature magnetic ordering. This prospect is, however, hindered by their inherent three-dimensional bonded nature. Here, we develop a confined-van der Waals epitaxial approach to synthesizing air-stable semiconducting cobalt ferrite nanosheets with thickness down to one unit cell using a facile chemical vapor deposition process. The hard magnetic behavior and magnetic domain evolution are demonstrated by means of vibrating sample magnetometry, magnetic force microscopy and magneto-optical Kerr effect measurements, which shows high Curie temperature above 390 K and strong dimensionality effect. The addition of room-temperature magnetic semiconductors to two-dimensional material family provides possibilities for numerous novel applications in computing, sensing and information storage.

Van der Waals crystals allow for magnetism down to the monolayer limit, however, this magnetism, and frequently the material itself, is fragile. Ferrites, conversely, have robust material stability and magnetic order, but are three dimensional. Here the authors succeed in creating a single unit cell thickness of Cobalt Ferrite via chemical vapour deposition, with hard magnetic properties, and curie temperature exceeding room temperature.