The investigation andengineering of novel multifunctional compounds, which show differentfunctionalities in the same phase, is one of the most impressive challenges intoday’s solid-state physics. The uses of such compounds assure for an improvedlevel of functionality while reducing the cost, size, and power consumption offuture engineered systems.
Multiferroic materials which aresimultaneously ferroelectric and ferromagnetic have involved a lot of attentiondue to their great potential applications in , transducers, magnetic sensors,storage media, and spintronics devices as they provide a novel approach to themagnetic/electric field conversion 1-3. These materials can be polarized in presence ofmagnetic field and magnetized in an electricfield 2. The type of interactionbetween ferromagnetic and ferroelectric phases is defined as magnetoelectric(ME) coupling. Single phase compounds have weak ME response, low workingtemperature, and the novel properties of the materials limit the application 4. Piezoelectric / piezomagneticcomposite are alternative materials that can fulfill the requirements ofapplications in which the ME response is enhanced via mechanical couplingbetween the piezoelectric and piezomagnetic phases 5. The magnetostrictioninduces a mechanical distortion with the effect of an applied magnetic field,which is further mediated by mechanical stress and as a result, an electricfield is induced due to the piezoelectric effect 6,7.A number ofmultiferroic composites such as BiFeO3/Bi0.
95Mn0.05FeO3–Ni0.5Zn0.5Fe2O48, MnFe2O4– BiFeO3 9, BiFe0.
5Cr0.5FeO3– NiFe2O4 10, (1–y) BiFeO3 – yNi0.50Cu0.05Zn0.
45Fe2O411, 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 bydifferent researchers at room temperatures by different methods and explorationon their structural, morphological, magnetic and electrical behaviours werecarried out.
As per our literature survey, reports on the synthesis of spinel-perovskitecomposites at room temperature were very limited. In addition to appropriatephase mixing, the heat treatment confirms the grain size reduction and enhancementis expected in the electrical and magnetic properties. In the presentinvestigation, 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 lithiumferrites arise as an attractive magnetic material because of their excellentproperties like high Curie temperature, squareness of hysteresis loop, high andwide range of saturation magnetization, low dielectric and magnetic losses etc.
They have significant magnetic and electrical properties for the applicationsof microwave devices, such as isolators, circulators and phase shifters 18. The Ni-Mn ferrites have high magnetostriction coefficient 19. Animprovement in the saturation magnetization, permeability and Néel temperature(TN) was observed by Mazen et al. 20in Li-Mn ferrites due to high spin Mn substitution. BiFeO3 is a promising room temperature multiferroicmaterial. It is the only material that presents a coupling between the magneticand electric ordering at room temperature 21. BFO is ferroelectric with a Curie temperature (TC) ? 1103K and antiferromagnetic withNeel temperature (TN) ? 643 K 22 At room temperature it exhibits rhombohedral distorted perovskitestructure.BFO has been proposed to be a potential candidate forenhanced magnetoelectric coupling.
But phase impurity, large dielectric loss, semiconductingbehavior, weak magnetoelectric coupling and cycloid spin structure limits theutility of BFO for practical applications 23. So, it is estimated that the net magnetisation and lossfactor of the material can be enhanced by making composites with themagnetically strong LNMFO 8. Spinel phase LNMFO has also been reported as a possiblecandidate in device miniaturisation and lower power consumption in microwavedevices 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) multiferroiccomposite have been synthesised successfully and their structural,morphological magnetic and dielectric properties were carried out. On adding ferritephase LNMFO, it is expected that the compositescontaining these two phases in different molar proportions may exhibit the dielectric constant and loss factor decreases to agreat extent and hence this characteristic may emerge as a new technologicalsolution for the ever increasing demand of device miniaturisation industry 25–27.