Using standard solid

state reaction method, multiferroic composite of 0.2 LNMFO + 0.8

BFO with LNMFO as ferrimagnetic and BFO as ferroelectric phase were prepared.

To prepare BFO stoichiometric amounts of high purity Bi2O3,

and Fe2O3 were weighed and mixed thoroughly in acetone

media for 5–6 h. The mixed BFO powder was calcined at 800°C for 4 h and then

pre-sintered at 850°C for 4 h. To prepare LNMFO high purity Li2CO3,

NiO, MnCO3 and Fe2O3 were mixed in stoichiometric

amounts by the same procedure as BFO. The mixed powder of LNMFO was calcined at

800 °C and pre-sintered at 1200 °C for 4 h. After pre-sintering, powders of BFO

and LNMFO were again grinded in an agate mortar. To prepare 0.2BFO + 0.8LNMFO

composite, the obtained BFO and LNMFO powders were mixed in weight proportions

in acetone media for 3–4 h. From the powders of composite pellet- and

toroid-shaped samples were prepared by applying a uniaxially pressure of 55MPa.

Finally at various sintering temperatures (Ts) the samples were

sintered for 4 h.

2.2 Characterizations

X-ray

diffraction (XRD) was studied using a X-ray diffractometer with CuK?

radiation (?= 1.5418 Å). Surface morphology was studied by Field Emission

Scanning Electron Microscopy (FESEM, model JEOL JSM 7600F). Energy Dispersive

X-ray Spectroscopy (EDX) analysis was done using the EDX system supplied with

the FESEM. The formula:

where m is the mass, r

is the radius and t is the thickness of the pellet, was used to obtain the bulk

density (?B) of the composite. The X-ray density of the

composite is given by the formula,

where

is 0.8 times molecular weight of BFO and

is 0.2 times molecular weight of LNMFO,

(ferroelectric) and

(ferrite) 22. The ?x was

measured using the formula,

, where n is the number

of atoms in a unit cell, M is the

molar mass of the sample, NA

is Avogadro’s number and V is the

volume of the unit cell. Using the relation,

, the porosity of the composite

was calculated. The electric and magnetic properties were carried out using

WAYNE KERR 6500B Impedance Analyzer. The samples were painted by conducting

silver paste on both sides to measure dielectric properties. The dielectric

constant (??) was calculated using the formula:

, where C is the

capacitance of the pellet, A is the cross-sectional area of the electrode and

(

= 8.85×10-12 F/m) is the permittivity in free space. To calculate

the ac conductivity (?ac), the relation:

, where, ? is the angular frequency and tan? is the dielectric loss, was used.

The Magnetic hysteresis loop was observed using a vibration sample magnetometer

(VSM, model Micro Sense, EV9). The real part of the complex initial

permeability

was

calculated using the relation:

, where Ls is

the self-inductance of the sample and

is derived geometrically. Here, L0 is the inductance of the winding

coil without the sample, N is the number of turns of the coil (N = 4), S is the

area of cross section and

is the mean diameter of the toroidal sample,

where d1 and d2 are the inner and outer diameter of the

toroidal sample, respectively 15. The output

voltage generated from the composite was measured using a Keithley multimeter

(Model 2000) with of dc magnetic field. ME voltage coefficient (?ME) was calculated using

relation 16

, where

is the ME voltage across the

sample surface and h0 is

the amplitude of the ac magnetic field.