Magnetism and magnetooptics features of Zn
1-x
Co
x
O
y
thin films
grown by pulsed laser deposition
A.S. Kuz’mina
a, *
, А.А. Lotin
b
, O.A. Novodvorsky
b
, N.S. Perov
c
, E.A. Gan’shina
c
,
L.A. Makarova
c
, A.S. Semisalova
c
, A.G. Shneider
a
, M.P. Kuz’min
a
, S.S. Kolesnikov
a
a
Irkutsk National Research Technical University, Irkutsk, 664074, Russia
b
ILIT RAS - the Branch of the Federal Scientific Research Center “Crystallography and Photonics” of RAS, Shatura, 140700, Russia
c
Lomonosov Moscow State University, Moscow, 119991, Russia
highlights
High-temperature ferromagnetism in Zn
1-x
Co
x
O
y
thin films has cluster nature.
Ferromagnetic properties of the films at room temperature vary non-monotonically.
Magneto-optical properties of the films depend on them thickness.
The shift of the magneto-optical spectra is caused by the interference.
article info
Article history:
Received 30 January 2017
Received in revised form
2 May 2017
Accepted 5 June 2017
Available online 6 June 2017
Keywords:
Zn
1-x
Co
x
O
y
thin films
Pulsed laser deposition
Magnetism
Magnetooptics
Spintronics
abstract
The results of a comprehensive study of structural, magnetic and magneto-optical properties of 10
e262 nm thick Zn
1-x
Co
x
O
y
films (x ¼ 0e0.3) grown on c-sapphire substrates by pulsed laser deposition
(PLD) method are present. It is revealed that all of the synthesized Zn
1-x
Co
x
O
y
films possess a wurtzite
structure with the following lattice parameters: a ¼ 3.2495 Å, c ¼ 5.2329e5.2485 Å. It is detected that
ferromagnetic properties of Zn
1-x
Co
x
O
y
films at room temperature vary non-monotonically with the
increase of Co concentration. The strongest ferromagnetic signal is observed in the Zn
0.87
Co
0.13
O
y
film due
to the largest number of metallic Co clusters formed in the sample. A further increase of dopant con-
centrations in the films leads to the oxidation of metallic Co and the development of the paramagnetic
Co
3
O
4
phase which result in the decrease of the ferromagnetic signal. It is determined that specific
magnetic characteristics of Zn
1-x
Co
x
O
y
samples do not depend on the film thickness. Characteristics of
transversal Kerr effect pertaining to cobalt concentration in Zn
1-x
Co
x
O
y
films as well as thickness of the
samples are studied for the first time. The correlation between the amplitude of the magneto-optical
signal and the magnetization value of the films is established.
© 2017 Elsevier B.V. All rights reserved.
1. Introduction
A recently discovered phenomenon of high-temperature ferro-
magnetism in thin films (T
C
298
C) based on the wide bandgap
zinc oxide semiconductor (E
g
¼ 3.37 eV) opens broad prospects of
its application in semiconductor spintronics and optoelectronics
[1e6]. These compositions, along with those based on the indium-
tin oxide [7e9] and titanium oxide [10,11], can be widely used in
the production of thin displays, data storage devices, thin film
transistors, solar batteries, luminophores, light-emitting diodes
and gas sensors [5,6,12].
Theoretical investigations [13,14] have shown that zinc oxide
doped with 3d-metals (Mn, Fe, Co, Cr, Ni) can possess reproducible
ferromagnetic properties at above room temperature. However,
existing experimental data are inconsistent. So far, there is no clear
understanding about the physical origin of high-temperature
ferromagnetism in Zn
1-x
Co
x
O
y
thin films. While some authors re-
ported amplification of a ferromagnetic signal in the films with the
increase in cobalt concentration (x) and/or thickness of a sample (d)
[15,16], others observed its non-monotonic variation [17]. The
analysis of various sources proves that magneto-optical properties
of Zn
1-x
Co
x
O
y
films pertaining to the cobalt concentration and
* Corresponding author.
E-mail address: kuzmina.istu@gmail.com (A.S. Kuz’mina).
Contents lists available at ScienceDirect
Materials Chemistry and Physics
journal homepage: www.elsevier.com/locate/matchemphys
http://dx.doi.org/10.1016/j.matchemphys.2017.06.015
0254-0584/© 2017 Elsevier B.V. All rights reserved.
Materials Chemistry and Physics 198 (2017) 291e296