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Applied Physics A (2018) 124:469
https://doi.org/10.1007/s00339-018-1871-3
Comparative study on the physical properties of transition metal-
doped (Co, Ni, Fe, and Mn) ZnO nanoparticles
A. A. Azab
1
· Ebtesam E. Ateia
2
· S. A. Esmail
3
Received: 19 February 2018 / Accepted: 24 May 2018
© Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract
Nano-crystalline of TM-doped ZnO with general formula Zn
0.97
TM
0.03
O (TM: Mn, Fe, Co, and Ni) was prepared using sol–
gel method. The dependence of crystal structure, morphology, and optical and magnetic properties on the type of transition
metals was investigated. The XRD investigation of pure and TM-doped ZnO nanoparticles samples confirms the formation
of single-phase hexagonal wurtzite structure. The estimated crystallite sizes are found in the range of 17 and 38 nm for the
doped and pure samples, respectively. The obtained data suggest that the dopant type plays a vital role in the physical prop-
erties of the investigated samples. The optical band-gap energy Eg has been calculated from near infrared (NIR) and visible
(VIS) reflectance spectra using the Kubelka–Munk function. Minimum value of 2.398 eV and maximum one of 3.29 eV were
obtained for Manganese-doped ZnO and pure ZnO, respectively. The analysis of XRD and VSM of the samples confirms that
the observed room-temperature (RT) ferromagnetism can be attributed to an intrinsic property of doped material sample and
not due to formation of any secondary phase. The magnetic results show that Mn is the most effective dopant for producing
ferromagnetism in nanoparticles of ZnO.
1 Introduction
Recently, there has been a new field called diluted mag-
netic semiconductors which deals with the spin degrees of
freedom and charge manipulation [1]. More development
applied on transition metal-doped semiconductor oxides
such as ZnO, SnO
2
, etc [2]. Among these various semi-
conducting oxides, ZnO is considered one from the most
important promising material for its unique properties of
high electron mobility and good transparent [3–5]. Further-
more, ZnO is lower in cost and is environmental friendly as
compared to other metal oxides [6]. Moreover, it is a special
material with a direct bandgap (3.37 eV) and large excit-
ing binding energy of 60 MeV. Because of its exceptional
electrical and optical properties, zinc oxide has been widely
used in many technological applications such as thin-film
transistors [7], gas sensors [8], transparent conductor [9],
biomedical [10], and piezoelectric application [11]. How-
ever, when it doped with transition elements with small ratio
forming diluted magnetic semiconductor oxides (DMOS), it
provides curie temperature Tc above room temperature [12].
Peng Zhan, Xaio Zhang [13, 14], and WU Kai et al. [15]
reported the formation of room-temperature ferromagnetism
RTFM in ZnO films depending on the oxygen vacancies,
crystal defects, and annealing conditions respectively. Until
now, there is an extreme contradiction around reasons which
is responsible for the observing ferromagnetic behavior.
Some researchers showed that the ferromagnetic behavior
caused by a secondary phases of transition metals [16, 17].
However, other researchers reported RTFM for transition
metal-doped ZnO depending on structure and morphology
included particle size, type of TM dopant ions, and the con-
centration of free electrons in 3d state of transition metals
[18]. One purpose of our study is to introduce a new era
for improving the magnetic properties of ZnO through the
sol–gel method of preparation to obtain more applicable
samples. Characterization of the synthesized samples was
investigated to study their morphologies, structural, optical,
and magnetic properties which specify successful doping of
transition metals in zinc oxide.
* A. A. Azab
aliazab@hotmail.com
1
Solid State Electronics Laboratory, Solid State Physics
Department, Physics Research Division, National Research
Centre, 33 El-Bohouth St., Dokki, Giza 12622, Egypt
2
Physics Department, Faculty of Science, Cairo University,
Giza, Egypt
3
Thebes Academy of Engineering, Basic Science Department,
Cairo, Egypt
@Phil_Robichaud
@deepthiw
@JoseServera