The as they provide a novel approach to the

The investigation and
engineering of novel multifunctional compounds, which show different
functionalities in the same phase, is one of the most impressive challenges in
today’s solid-state physics. The uses of such compounds assure for an improved
level of functionality while reducing the cost, size, and power consumption of
future engineered systems. Multiferroic materials which are
simultaneously ferroelectric and ferromagnetic have involved a lot of attention
due to their great potential applications in , transducers, magnetic sensors,
storage media, and spintronics devices as they provide a novel approach to the
magnetic/electric field conversion 1-3. These materials can be polarized in presence of
magnetic field and magnetized in an electric
field 2. The type of interaction
between ferromagnetic and ferroelectric phases is defined as magnetoelectric
(ME) coupling. Single phase compounds have weak ME response, low working
temperature, and the novel properties of the materials limit the application 4. Piezoelectric / piezomagnetic
composite are alternative materials that can fulfill the requirements of
applications in which the ME response is enhanced via mechanical coupling
between the piezoelectric and piezomagnetic phases 5. The magnetostriction
induces a mechanical distortion with the effect of an applied magnetic field,
which is further mediated by mechanical stress and as a result, an electric
field is induced due to the piezoelectric effect 6,7.

A number of
multiferroic composites such as BiFeO3/Bi0.95Mn0.05FeO3

Ni0.5Zn0.5Fe2O4
8, MnFe2O4
– BiFeO3 9, BiFe0.5Cr0.5FeO3
– NiFe2O4 10, (1–y) BiFeO3 – yNi0.50Cu0.05Zn0.45Fe2O4
11, CoFe2O4
– BaTiO3 12, x Bi0.95Mn0.05FeO3 ? (1-x)
Ni0.5Zn0.5Fe2O4 13, Ni0.8Zn0.2Fe2O4
? Ba0.6Sr0.4TiO3 14, x Ni0.75Co0.25Fe2O4
? (1–x)BiFeO3 15, BiFeO3 ? NiFe2O4 16, Ni0.75Zn0.25Fe2O4
? BiFeO3 17 have been produced by
different researchers at room temperatures by different methods and exploration
on their structural, morphological, magnetic and electrical behaviours were
carried out. As per our literature survey, reports on the synthesis of spinel-perovskite
composites at room temperature were very limited. In addition to appropriate
phase mixing, the heat treatment confirms the grain size reduction and enhancement
is expected in the electrical and magnetic properties. In the present
investigation, the spinel phase Li0.1Ni0.2Mn0.6Fe2.1O4
(LNMFO) has been chosen as the ferromagnetic part and perovskite phase BiFeO3
(BFO) as the ferroelectric part in making composites. Lithium ferrite and mixed lithium
ferrites arise as an attractive magnetic material because of their excellent
properties like high Curie temperature, squareness of hysteresis loop, high and
wide range of saturation magnetization, low dielectric and magnetic losses etc.
They have significant magnetic and electrical properties for the applications
of microwave devices, such as isolators, circulators and phase shifters 18. The Ni-Mn ferrites have high magnetostriction coefficient 19. An
improvement in the saturation magnetization, permeability and Néel temperature
(TN) was observed by Mazen et al. 20
in Li-Mn ferrites due to high spin Mn substitution. BiFeO3 is a promising room temperature multiferroic
material. It is the only material that presents a coupling between the magnetic
and electric ordering at room temperature 21. BFO is ferroelectric with a Curie temperature (TC) ? 1103
K and antiferromagnetic with
Neel temperature (TN) ? 643 K 22 At room temperature it exhibits rhombohedral distorted perovskite
structure.
BFO has been proposed to be a potential candidate for
enhanced magnetoelectric coupling. But phase impurity, large dielectric loss, semiconducting
behavior, weak magnetoelectric coupling and cycloid spin structure limits the
utility of BFO for practical applications 23. So, it is estimated that the net magnetisation and loss
factor of the material can be enhanced by making composites with the
magnetically strong LNMFO 8. Spinel phase LNMFO has also been reported as a possible
candidate in device miniaturisation and lower power consumption in microwave
devices 24.
In this work, x Li0.1Ni0.2Mn0.6Fe2.1O4
+ (1–x) BiFeO3 (x=0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) multiferroic
composite have been synthesised successfully and their structural,
morphological magnetic and dielectric properties were carried out. On adding ferrite
phase LNMFO, it is expected that the composites
containing these two phases in different molar proportions may exhibit the dielectric constant and loss factor decreases to a
great extent and hence this characteristic may emerge as a new technological
solution for the ever increasing demand of device miniaturisation industry 25–27.

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