Vol.:(0123456789) 1 3
Journal of Materials Science: Materials in Electronics
https://doi.org/10.1007/s10854-019-02470-y
Preparation and magnetization dynamics of CoFe
2
O
4
–SrFe
12
O
19
nanocomposites
Kalyani Dhabekar
1
· K. Mohan Kant
1
Received: 16 May 2019 / Accepted: 29 October 2019
© Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract
Composites of diferent weight ratios were prepared from CoFe
2
O
4
and SrFe
12
O
19
nanoparticles. The pure phase formation
was confrmed by X-ray difraction analysis. The average crystallite size of the individual CoFe
2
O
4
and SrFe
12
O
19
nano-
particles were found as 17 nm and 43 nm, respectively. Exchange interaction in prepared composites is corroborated with
the M-H curves. First order reversal curve measurements have been performed for the prepared composites to establish
exchange interaction.
1 Introduction
Exchange spring oxide magnetic materials are widely stud-
ied due to their improved magnetic properties. The energy
product (BH)
max
in permanent magnets quantifes the amount
of work performed. (BH)
max
is restricted by the magnitude
of
M
2
r
4
0
, where M
r
is the remanent magnetization which is an
intrinsic characteristic of the material [ 1]. Preparing
exchange coupled magnetic materials by tailoring the satura-
tion magnetization (M
s
) and coercivity (H
c
) leads to enhance-
ment of the energy product (BH)
max
by utilizing the high
saturation magnetization of the soft magnetic phase and
large coercivity of the hard magnetic phase [1–3]. Irrespec-
tive of the high energy product (thereotically ∼ 120 MGOe)
of metallic permanent magnet systems (Nd–Fe–B and
Sm–Co systems), certain limitations such as high synthesis
cost and low corrosion resistance hinders their applications
[ 4]. In this regard, hard ferrites are more applicable.
Although owing to their low energy products, the concept of
exchange spring is used [1].
In the present article, cobalt ferrite (CoFe
2
O
4
) and stron-
tium ferrite (SrFe
12
O
19
) were used as soft and hard mag-
netic phases, respectively, to prepare CoFe
2
O
4
– SrFe
12
O
19
composites. Cobalt ferrite and strontium ferrite crystallizes
in a cubic inverse spinel structure (space group Fd3m )
and hexagonal magnetoplumbite structure (space group
P6
3
∕mmc) [5–7]. In isotropic two phase magnets, the size
of soft grains is predicted to be twice the domain wall width
of the hard magnetic phase for sufcient exchange coupling
due to incorporation of magnetic hardness by the hard phase
into the soft phase [2]. The exchange interaction in compos-
ites comprising of soft phased cobalt ferrite and hard phased
strontium ferrite was investigated. The strength of exchange
interaction is corroborated from
dM
dH
vs.H curves and also
from the First order reversal curve (FORC) measurements
of the prepared composites.
2 Experimental details
2.1 Materials
The chemicals used during synthesis include cobalt(II)
chloride hexahydrate (CoCl
2
⋅6H
2
O), strontium(II) chloride
hexahydrate (SrCl
2
⋅6H
2
O), iron(III) chloride hexahydrate
(FeCl
3
⋅6H
2
O) and sodium hydroxide (NaOH). All the rea-
gents were procured from Alfa Aesar (purity ≥ 99.9%) and
were used without any further purifcation. Distilled water
was used during the synthesis process.
2.2 Synthesis of CoFe
2
O
4
nanoparticles
Cobalt ferrite (CoFe
2
O
4
) nanoparticles were produced by
co-precipitation of Co
2+
and Fe
3+
ions with NaOH as the
* Kalyani Dhabekar
dhabekarkalyani27@gmail.com
K. Mohan Kant
k.mohankant@gmail.com
1
Department of Physics, Visvesvaraya National Institute
of Technology, Nagpur, Maharashtra 440010, India