300 K Ferromagnetic Magnetic Circular Dichroism in Co2+-doped ZnO Activated by Shallow Donors

TL;DR

This study demonstrates room-temperature ferromagnetic behavior in Co-doped ZnO films, activated by shallow donors, with MCD spectroscopy revealing a broad ferromagnetic signal linked to impurity band transitions.

Contribution

It provides new insights into ferromagnetism in Co-doped ZnO induced by shallow donor states, highlighting the role of impurity bands in magnetic properties.

Findings

Ferromagnetic MCD observed at 300 K between 1.4 and 4.0 eV.

Shallow donors activated ferromagnetism after zinc vapor exposure.

Ferromagnetic signal linked to spin-split impurity band transitions.

Abstract

Cobalt-doped ZnO (Co2+:ZnO) films were studied by magnetic circular dichroism (MCD) spectroscopy. A broad 300 K ferromagnetic MCD signal was observed between 1.4 and 4.0 eV after introducing shallow donor states by exposure of paramagnetic Co2+:ZnO films to zinc vapor. The new sub-bandgap ferromagnetic MCD intensity is attributed to low-energy photoionization transitions originating from a spin-split donor impurity band in ferromagnetic Co2+:ZnO.