An oxide-diluted magnetic semiconductor: Mn-doped ZnO

Abstract

Epitaxial thin films of an oxide-diluted magnetic semiconductor, Mn-doped ZnO, were fabricated by pulsed-laser deposition technique. Solubility of Mn into ZnO exceeds thermal equilibrium limit as a result of nonequilibrium film growth process. As Mn content is increased, the lattice constants of both a and c axes of wurtzite Zn1−xMnxO films (x<0.35) increase and the band gap expands although considerable in-gap absorption develops. Itinerant electrons over 1019 cm−3 can be doped into the Zn1−xMnxO films by Al doping, in contrast to low carrier density in the other II–VI diluted magnetic semiconductors. The temperature dependence of the resistivity is almost metallic and considerable magnetoresistance is observed at low temperatures.

Synthesis of Colloidal Mn2+: ZnO Quantum Dots and High‐Tc Ferromagnetic Nanocrystalline Thin Films.

“…All data were corrected for the diamagnetism of the substrate and sample holder. Figure 1a shows electronic absorption spectra of a 0.10 M DMSO solution of 2% 17,22,37,38 The solid line in Figure 1a shows the spectrum collected after 1.65 equiv of base were added. Base addition beyond ca.…”

“…2, 3 Many earlier studies of Mn 2+ :ZnO revealed only paramagnetism, or at best ferromagnetism below RT, with T C ranging from 37 K to 250 K, and many have low saturation moments indicative of only partial magnetic ordering. 10,[16][17][18] The wide range of magnetic properties displayed by this and other ZnO DMSs prepared by apparently similar methods 10,19 suggests that the criteria necessary for ferromagnetism are highly sensitive to the preparation conditions and ultimately to the materials composition. Developing reproducible methods for preparing high-T C ferromagnetic DMSs is essential for their use in spintronics technologies but remains a central challenge in this field.…”

“…We speculate that direct chemical syntheses of ZnO DMSs can provide better control over materials composition than is obtained with some high-temperature vacuum deposition and solid-state synthetic techniques, which often use dopant source materials that are themselves undesirable contaminants (e.g. manganese oxides for Mn 2+ :ZnO, 15,17 NiO for Ni 2+ :ZnO, 20 and cobalt oxides or Co metal for Co 2+ :ZnO 21 ) or require high temperatures and reducing conditions that may promote segregation of metallic precipitates. 13,18 The advantage of the direct chemical approach is illustrated in the case of Ni 2+ :ZnO.…”

Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory

“…26 Most of the experimental results show that, among transition-metal dopants, Co-doped ZnO systems are ferromagnetic in both thin films as well as bulk materials. 13,16,27 Also, there have been few reports of ferromagnetism in Mn-, 28,29 Ni-, 30 and some other TM-doped 31 ͑such as Cr or V͒ ZnO. The ferromagnetism in the Mn-doped system is yet to be understood, as Mn in the +2 valence state does not dope any carrier into the ZnO system and hence, by first-principles studies, 24 must lead to an antiferromagnetic ground state.…”

Structure and magnetic properties of Mn-doped ZnO thin films

“…It is believed that Mn has higher solubility in ZnO thin fi lms grown by pulsed laser deposition (PLD), which is a non-equilibrium process [11]. Fabrication of Mn-doped ZnO thin fi lms without manganese oxides can facilitate the investigation and understanding of the magnetic properties of this material.…”