Room-temperature ferromagnetism in Li-dopedp-type luminescent ZnO nanorods

Abstract

We have observed ferromagnetism in Li-doped ZnO nanorods with Curie temperature up to 554 K. Li forms shallow acceptor states in substitutional zinc sites giving rise to p-type conductivity. An explicit correlation emerges between increase in hole concentration with decrease in magnetization and Curie temperature in ZnO:Li. Occurrence of ferromagnetism at room temperature has been established with observed magnetic domain formation in ZnO:Li pellets in magnetic force microscopy and prominent ferromagnetic resonance signal in electron paramagnetic resonance spectrum. Magnetic ZnO:Li nanorods are luminescent, showing strong near UV emission. Substitutional Li atoms can induce local moments on neighboring oxygen atoms, which when considered in a correlated model for oxygen orbitals with random potentials introduced by dopant atom could explain the observed ferromagnetism and high Curie temperature in ZnO:Li nanorods.

High temperature carrier controlled ferromagnetism in alkali doped ZnO nanorods

“…For ZnO:Li, hole concentration and resistivity varied from 1.6ϫ 10 16 to 1.3 ϫ 10 19 cm −3 and 107.5 to 43.7 k ⍀ cm, respectively, for variation in Li concentration from 2% to 15%. 15 The results unambiguously indicate that the hole concentration increases and resistivity decreases with increase in Li concentration and accord with earlier reports 16,17 on Li doped ZnO thin film deposited at 500°C. These indicated effective substitution of Li in zinc sites leading to p-type conductivity.…”

“…% Li doped ZnO. 15 ZnO:Li ͑2 at. %͒ sample exhibited a hysteresis loop with Curie temperature as high as 554 K. The hysteresis loop for ZnO:Na ͑2 at.…”

Intense violet–blue emission and paramagnetism of nanocrystalline Gd3+ doped ZnO ceramics

“…5). Similar emission quenching has been reported in alkali doped ZnO nanorods [26]. The optical transition that is responsible for Gd 3+ emission is 6 P J → 8 S 7/2 (4f-4f transition), so the incorporation of Gd 3+ could improve the emission intensity of rare earth ions.…”

Lithium doping and photoluminescence properties of ZnO nanorods

“…Although there are few reports on Li doped ZnO thin films 13 and nanostructures. 14,15 Here in this letter, we report the growth and Li doping of ZnO NRs by a low temperature thermal decomposition method, which is a cost effective and rapid synthesis method for fabricating ZnO NRs. This growth method have some advantages compared with other growth methods, such as use of simple equipment, low temperature deposition, low cost, less hazardous, and does not require catalyst.…”