Ferromagnetism in Co-doped ZnO films grown by molecular beam epitaxy: magnetic, electrical and microstructural studies

TL;DR

This study investigates the magnetic, electrical, and microstructural properties of Co-doped ZnO films grown by MBE, revealing room-temperature ferromagnetism mediated by free electrons and highlighting the interplay between charge carriers and magnetism.

Contribution

It provides detailed insights into the ferromagnetic behavior of Co-doped ZnO films grown by MBE, emphasizing the role of free electrons in magnetic coupling.

Findings

Ferromagnetism observed up to room temperature

Carrier mobility influenced by electron coupling

Microscopic mechanism involves free electron-mediated spin coupling

Abstract

We studied structural, optical and magnetic properties of high-quality 5 and 15% Co-doped ZnO films grown by plasma-assisted molecular beam epitaxy (MBE) on (0001)-sapphire substrates. Magnetic force microscopy (MFM) and magnetic measurements with SQUID magnetometer show clear ferromagnetic behavior of the films up to room temperature whereas they are antiferromagnetic below 200 K approximately. Temperature dependence of the carrier mobility was determined using Raman line shape analysis of the longitudinal-optical-phonon-plasmon coupled modes. It shows that the microscopic mechanism for ferromagnetic ordering is coupling mediated by free electrons between spins of Co atoms. These results bring insight into a subtle interplay between charge carriers and magnetism in MBE-grown Zn(1-x)CoxO films.