Ferromagnetic order in aged Co-doped TiO2 anatase nanopowders

TL;DR

This study demonstrates that Co-doped TiO2 anatase nanopowders retain significant ferromagnetic properties even after two years, indicating stable long-range magnetic order suitable for spintronic applications.

Contribution

It provides evidence that aged Co-doped TiO2 anatase nanopowders maintain ferromagnetism over long periods, addressing stability concerns in DMS materials.

Findings

Aged samples show high magnetization, remanence, and coercivity.

Long-range ferromagnetic order persists after two years.

Higher Co content may lead to metastability and Co segregation.

Abstract

Oxide based diluted magnetic semiconductor (DMS) materials have been a subject of increasing interest due to reports of room temperature ferromagnetism in several systems and their potential use in the development of spintronic devices. However, concerns on the stability of the magnetic properties of different DMS systems have been raised. Their magnetic moment is often unstable, vanishing with a characteristic decay time of weeks or months, which precludes the development of real applications. This paper reports on the ferromagnetic properties of two-year-aged Ti1-xCoxO2-{\delta} reduced anatase nanopowders with different Co contents (0.03<x<0.10). Aged samples retain rather high values of magnetization, remanence and coercivity which provide strong evidence for a quite preserved long-range ferromagnetic order. In what concern Co segregation, some degree of metastability of the diluted Co doped anatase structure could be inferred in the case of the sample with the higher Co content.