Structural and magnetic properties of transition metal substituted ZnO

TL;DR

This study investigates the structural and magnetic properties of transition metal-doped ZnO, finding no bulk ferromagnetism in single-phase samples and highlighting the effects of synthesis conditions on magnetic behavior.

Contribution

It provides new insights into the magnetic properties of TM-doped ZnO, emphasizing the absence of ferromagnetism in ideal samples and the role of secondary phases.

Findings

Single-phase Zn_{1-x}TM_xO shows paramagnetic behavior.

Secondary phases cause spin-glass or ferromagnetic behavior.

Synthesis conditions influence magnetic properties and phase formation.

Abstract

Structural and magnetic properties have been studied for polycrystalline Zn_{1-x}TM_xO, where TM (transition metal ions) = Mn, Fe, and Co. No bulk ferromagnetism was observed for single-phase materials, contrary to the existing theories. Single-phase samples demonstrate paramagnetic Curie-Weiss behavior with antiferromagnetic interactions, similar to other diluted magnetic semiconductors. Non-optimal synthesis conditions lead to formation of second phases that are responsible for spin-glass behavior (ZnMnO_3 impurity for Zn_{1-x}Mn_xO (S. Kolesnik et al., J. Supercond.: Incorp. Novel Magn. 15, 251 (2002)) or high-temperature ferromagnetic ordering (Co metal for Zn_{1-x}Co_xO with the Curie temperature T_C > 800 K or (Zn,Fe)_3O_4 for Zn_{1-x}Fe_xO with T_C = 440 K).