Mechanical alloying: a route to room-temperature Ferromagnetism in bulk Zn1-xMnxO

• Published in: Journal of magnetism and magnetic materials 2004-11, Vol.283 (1), p.117-127
• Main Authors: Blythe, H.J., Ibrahim, R.M., Gehring, G.A., Neal, J.R., Fox, A.M.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Dilute magnetic semiconductors; Exact sciences and technology; Ferromagnetism; Magnetic properties and materials; Magnetic semiconductors; Materials science; Materials synthesis; materials processing; Mechanical alloying; Physics; Studies of specific magnetic materials
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2004.08.008

High-purity commercial ZnO and MnO2 powders have been used as starting materials for the production of the compound Zn0.98Mn0.02O. The magnetic properties of these source materials have been investigated before a powder-mix corresponding to Zn0.98Mn0.02O was mechanically alloyed for periods of up to 15h. It is found that the effect of grinding the two powders together generates a ferromagnetic component that exhibits hysteresis at room temperature. At 290K, the component has a coercivity of 110±10 Oe and saturates in a field of about 6kOe. The magnetic moment per Mn atom is estimated to be about 0.1μB. On low-temperature anneal, there is a slight increase in the saturation magnetisation of the compound until, after anneal at 700∘C, the ferromagnetism has decayed and, at room temperature, the powder-mix shows a nett paramagnetic behaviour. On a further anneal at temperatures up to 1000∘C, several low-temperature peaks are observed in low-field measurements. We interpret these as arising due to the thermal decay of the MnO2 and its subsequent interaction with ZnO. No room-temperature ferromagnetism is observed after anneal at 700∘C.