multiferroic materials

1. • Ferroelectric materials
Ferroelectric materials possess
spontaneous electric polarization that
can be reversed by the application of
an external electric field.
Condition: Central metal atom
should have do configuration.
e.g: Barium titanate, PZT etc
Applications
• Ferroelectric random access
memories (FeRAMs).
• High density memories.
• Sensors
• Actuators and infra-red detectors.
• Ferromagnetic
materials
Ferromagnetic materials possess
spontaneous magnetization that can
be reversed by the application of an
external magnetic field.
Condition: Central atom should
have dn (n=1,2,3…) configuration.
Applications
• Wireless communications
• Space research
• Storage devices
• Magnetic recording
J. F. Scott, Science ,315, 954 (2007);
H. Sakai, et al., Phys. Rev. Lett. 107, 137601(2011).
Y. D. Kolekar et al, J.Appl.Phys., 115, 144106,
(2014)
Introduction

2. Electric, magnetic and magneto-electric
properties of Ferrite-Ferroelectric composites

3. SINGLE PHASE
Ferrite-Ferroelectric
composite
Both magnetic and dipolar
order exist in the same material
Heterointerfaces of two different
materials (one FE & another FM
Possibilities to combine Ferroelectric and magnetic phase
C. Nan et al,J.Appl. Phys.,103, 031101, (2008)
Y.Wang, C.Nan, NPG Asia Materials, 2, 61-68, (2010).
C. S. Antoniak, et al Nat. Commun. 4, 2051 (2013)
J.Tao, X.Luo, N. Zhang, J.Appl.Phys., 117, 113904(2015)
Applications
Multiple state memory elements,
Data is stored both in the electric and the magnetic polarizations.
 Electrical filters.
High density memories.
Combine high speed ferroelectric RAM magnetic RAM.

4. H. Schmid , Ferroelectrics 162(1994)317;.
Jia-Mian et al , Adv. Mater. 28(2016) 15; [3] Carlos et al , Adv. Mater. 22(2010) 2900
Some of the limitations of Single Phase Multiferroics:
• Small magneto-electric coupling in single phase multiferroic materials.
• The range of single phase multiferroic materials is limited by crystal symmetry [1]. (BiFeO3, YMnO3,
Fe2O3).
• RT magneto-electric coupling in single phase multiferroics has been a challenging task .
J.Kaur, J.Shah, R.K.Kotnala, Adv. Mat.Lett. 2012, 3, 371-375.
Multiferroic Composites:
• Compared to single-phase multiferroics, multiferroic heterostructures (composites) show a strong room
temperature ME effect.[2]
• One can use strain to couple the ferroelectric phase ( via piezoelectric effect) to the magnetic phase (via
magnetostriction)
• By using a ferroelectric material with large piezoelectric coefficient( e.g., BaTiO3, PZT) , a magnetic
material with large magnetostriction and large resistivities (e.g. CoFe2O4, NiFe2O4), appreciable
magnetoelectric coupling can be achieved.
Why I preferred Ferrite-Ferroelectric composite

5. Ferrite-Ferroelectric composites
Ferrite Ferroelectric
Will be discussed
by nasir

6. Based on the crystal structure ,ferroelectrics are classified into four general distinguished
categories:
Corner Sharing Octahedral
Compound containing hydrogen bonded
radicals
Organic Polymers
Ceramic Polymers Composites
Classification of Ferroelectrics
Shashaank Gupta,et al 2021.

7. Corner Sharing Octahedra(CSO):
• This class of ferroelectric crystals
consists of mixed oxides including
corner sharing octahedra of O2- ions.
• In this type of crystals , the
ferroelectricity is achieved by a
lattice distortion .
• Based on structure of unit cell CSO
are of four types :
Perovskite group
Tungsten bronze group
Layer structure group
Pyrochlore group

8. • Among the various ferroelectrics, Perovskite group have emerged as the most promising and efficient low
cost energy materials for various optoelectronic and photonic device applications .
• Transition metals perovskite are the most suitable materials for the field of multiferrioc work .
• The discovery of calcium titanate (CaTiO3) in 1839 by a Russian mineralogist PEROVSKI was considered
to be the origin of perovskite .
• The general chemical formula used to describe the perovskite materials is ABX3 ,where A and B are
cations with A larger than that of B and X is anion usually oxides or halogens.
• Some of the examples of perovskite materials are:
Lead Zirconate Titanate (Pb(Zr,Ti)O3/ PZT),
Barium Titanate (BaTiO3)/(BT)
Lead Lanthanum Zirconate (Pb,La)(Zr,Ti)O3
• BTO show large ferroelectric effect and is vastly studied.
Perovskite Group
Shashaank Gupta,et al 2021.

9. • Barium titanate (BaTiO3) has a perovskite ABO3 type structure , the central Ti atom is
surrounded by six oxygen ions in an octahedral.
• Unilateral displacement of the positively charged Ti4+ ions against surrounding O2- ions
occurs to give rise to net dipole moment .
Barium Titanate
G. H. Kwei, A. C. Lawson, S. J. L. Billinge, and S. W. Cheong J. Phys. Chem. 1993, 97, 10, 2368–2377

10. Four phases of BaTiO3
Temperature dependence of
dielectric constant for BaTiO3
G. H. Kwei, A. C. Lawson, S. J. L. Billinge, and S. W.
Cheong J. Phys. Chem. 1993, 97, 10, 2368–2377
Dielectric constant of BTO as a function of temperature
measured along a-axis and c- axis.
2. F. Jona, G. Shirane, Dover Publications, INC., New York, 1993

12. Literature Review on Ferrite-ferroelectric
composites in which Barium titinate is chosen as
one of the phase

13. Structural, electric, magnetic, and magneto-dielectric properties of (12x)
Ba0.95Yb0.05TiO3-(x)NiFe1.95 Yb0.05O4 multiferroic composites
Fig. 6 a Variation of dielectric constant with temperature for composites (S1, S2, S3 and
S4) and b shows the variation of tand with temperature
Fig. 7 a P-E hysteresis loops of the multiferroic composites (S1, S2, S3 and S4), b Variation of electrical coercivity (Ec) and saturation polarization
(Pmax) with NFYbO phase percentage
• P-E hysteresis loop with a maximum polarization
of 6.44 lC/cm2
is observed for S1
• The Pmax reaches 6.44 lC/cm2
of the composite S1,
which decreases to 2.262 lC/cm2
for S4 composite
• From the ferroelectric hysteresis loops (P-E loops), all the
P-E loops of the prepared composited are not very well
saturated. However, excellent ferroelectric behavior was
observed

14. Literature Review on BaTiO3 as one of the phase for the formation of
Multiferroic composite
• Multiferroic composite materials based on antimony doped barium titanate/nickel ferrite were prepared by a
mixing route.
• Dielectric permittivity enhancement in comparison with composites prepared
from pure barium titanate was noticed.
• Well defined hysteresis loops have shown the changes of properties induced by
the modification of the barium titanate phase with Sb doping and due to the co-
existence of two different phases in the materials.
• Magnetic properties enhanced in comparison with composites prepared from
pure BT.

15. Ferroelectric and magneto-dielectric properties of yttrium doped
BaTiO3–CoFe2O4 multiferroic composite
Multiferroic composites of ferroelectric and ferrite phases having general formula xCoY0.1Fe1.9O4—(1−x) Ba0.95Y0.05TiO3
(where x=0.05, 0.1 and 0.15) were prepared using the conventional solid-state reaction method.
• Dielectric studies of the composites, in the temperature range 100–550 K
revealed two ferroelectric phase transitions.
Fiig Variation of dielectric constant and tanδ with temperature YBC1
Fig.11 (a) Room temperature P–E hysteresisloops for YBC1, YBC2 and YBC3.
• All the composites showed P–E hysteresis loops; which confirm the
ferroelectric nature of the composites.
• The variation of tanδ with temperature for YBT shows a similar
behaviour as that of ε′, supporting a ferroelectric phase transition

16. Ferrite-Ferroelectric composites
Ferrite Ferroelectric
Discussed by ruqiya

17.  They belongs to well known class of ferrimagnetic materials
Introduction
 The term ferrite is commonly used to describe a class of magnetic
oxide compounds that contains iron oxide (Fe2O3) as a principal part.
 Ferrites are Generally represent by the chemical formula MOFe2O3,
M being the divalent cations, like Fe, Co, Ni, Zn etc.
 Ferrites crystallized in the form of a cubic structure.
Ferrite structure
Tetrahedral site
Octahedral sites
Oxygen atoms

18. Ferrites
Spinel
Ferrites
Garnet Hexaferrite Orthoferrite
Based on different crystal forms ferrites are classified as
Normal/Inverse

19. Spinel Ferrites
 Spinel ferrites are generally represented by the chemical formula
AB2O4
 Their structure is similar to that of naturally occurring MgAl2O4
which goes by the name ‘‘spinel’’.
The chemistry and physics of A and B cations dictate the
electrical and magnetic properties of ferrites.
 The exchange interaction between
A and B sites is negative and is
strongest among the cations, so that
the net magnetization results from
the difference in magnetic moment
between A and B sites.
𝑂2−

20. Unit cell of Spinel ferrites
• 64-tetrahedral sites and 32-octahedral sites
• A-site is surrounded by 4 Oxygen atoms
• B-site is surrounded by 6 Oxygen atoms
Octahedral B-site
Tetrahedral A-site
Octahedral site
Oxygen
Tetrahedral site
 Based on the occupancy of cations at the tetrahedral (A) and octahedral (B) site
Spinel ferrites are classified as
Spinel
Ferrites
Normal
(A)[B2] O4
Inverse
(B)[AB] O4
Mixed
(AB)[AB] O4
Spinel ferrite cont.…

21. Inverse Spinel structure of ferrites
 Cubic ferrite Fe2+O2- _(Fe3+)2(O2-)3 has inverse spinel
crystal structure with cubic symmetry.
 Structure is represented by (FeIII)tet(FeIIFeIII)octO4.
 Saturation Magnetisation= spin magnetic moment for
each Fe2+ ion × number of Fe2+ ions.
 Half of trivalent (Fe3+) are located at tetrahedral and
another half at octahedral positions with spins
opposite and cancel effect of each other.
 Divalent Fe2+ at the tetrahedral positions have spins in
the same direction and contribute to total magnetic
moment.
Cation Octahedral
site
Tetrahedral
site
Net Magnetic
moment
Fe3+ ↑↑↑↑↑↑
↑↑↑↑↑↑
↓↓↓↓↓↓
↓↓↓↓↓↓
complete
cancellation
Fe2+ ↑↑↑↑↑↑
↑↑↑↑↑↑
↑↑↑↑↑↑
↑↑↑↑↑↑
Distribution of Spin Magnetic Moments for Fe2+ and Fe3+ ions in a Unit Cell Fe3O4.
Schematic diagram showing spin magnetic moment for Fe2+ and
Fe3+ ions in Fe3O4

22. Why Spinel Ferrites
Spinel ferrites, which contain iron oxide, are magnetic
ceramics with a vast potential for numerous scientific and
technological applications.
It constitutes an important class of magnetic materials
having several technological applications like spintronics,
magnetic diagnostic, magnetic drug delivery, storage
devices, electrical generators, microwave devices, and so
forth.
The chemistry and physics of M and Fe cations
(M2+Fe2
3+O4
) dictate the electrical and magnetic properties of
ferrites.

23. Why Cobalt Ferrite
Cobalt ferrite CoFe2O4 (CFO) is the most useful hard
ferrimagnetic material, which exhibits unique properties such
as
 Strong spin−orbit (L−S) coupling,
high Curie temperature,
high coercivity,
high magneto-crystalline anisotropy,
moderate saturation magnetization,
good mechanical hardness, and
Chemical stability.
Higher values of magnetostriction make CFO a potential
candidate material for “strain sensor and actuator”
applications.

24. Why transition metal ion doped Cobalt Ferrite
 Recently, the doping of small amount of trivalent rare earth cations in spinel ferrite has emerged as a
promising strategy to improve the magnetic and electrical properties.
 Moreover, these properties are governed by the antiferromagnetic super exchange interaction
between Fe3+- Fe3+ ions; introducing small amount of trivalent rare earth (RE) ions into the spinel
ferrite lattices will also induce RE3+- Fe3+ interactions.
 Rare-earth ions play an important role in determining the magneto-crystalline anisotropy in 4f-3d
intermetalic compounds.
 Rare-earth ions have stronger S-L coupling and weaker crystal field, so they have stronger
magnetocrystalline anisotropy.
 Moreever, the radii of rare-earth ions are larger then that of Fe3+ ions, hence the symmetry of crystal
will be decreased after the sample was substituted by rare-earth ions.
 The low symmetry of crystal will lead to strong magnetostriction.
 The doping of small amount of divalent transition/rare earth metal ion cations in spinel ferrite has
emerged as a promising strategyto improve the magnetic and electrical properties.
 The symmetry of crystal will be decreased after the sample was substituted by these metal ions
and leads strong magnetostriction.
 Higher magnetic moment of Mn (6µB )than Fe (5µB) results to the
improved magnetic properties
 Dielectric loss decreases.

25. Hysterises in ferromagnets

26. Synthesis and characterization of BaTiO3-CoFe2O4 composites
(100-x) BaTiO3 (BT)-(x) CoFe2O4 (CFO) (X D 10, 20 and 30 wt%) composites were prepared through conventional solid
state reaction method by mixing two individual phases by weight
• CoFe2O4 phase made the composite more lossy with increase of its content.
From the figure it can be observed clearly that as the CFO content increased
the system became more lossy as well as transformed it from normal ferro-
electric to relaxor type of ferroelectric
• There the Tc observed for BTO shifted towards higher temperature with
increase of frequency. Hence we may conclude that CFO influences the
ferroelectric nature of BT
Fig:-Temperature dependant of dielectric characteristics of (100-x) BT–x CFO composites.
 Dielectric Studies
• Dielectric properties of parent BT and BT-CFO composites are
shown in the Fig. It is clearly shown in the figure that BT exhibits
normal ferroelectric behaviour and the transition temperature is at
138.5◦C

27.  Ferroelectric propertie
Fig:-Ferroelectric hysteresis loops obtained for the ceramic BTand composites at various fields.
• Fig:- shows the ferroelectric properties of the parent BT and BT-CFO
composites were examined by measuring the polarizations (P)
against the electric field (E) up to 30 Kv/cm,
• saturated hysteresis loop was observed for parent BT whereas
(100-x) BT C x CFO (x D 10, 20 and 30 wt%) composites do not
show the saturation.
• The maximum polarization (Pmax) and remnant polarization
(Pr) values for parent BT are 13.76 mC/cm2
and 7.17 mC/cm2
,
respectively
• The increase in the coercive field for composites with increase of
CFO phase indicates that the conducting nature of the composite
predominates over ferroelectric nature.
• The Pmax and Pr values for 90 BT10CFO composite are 4.10
mC/cm2 and 1.01 mC/cm2 respectively. But as CFO content
increased the loops appear to be lossy.

28. Figure 5. Magnetoelectric output verses magnetic fieldfor (100-x) BT-xCFO(xD 10, 20 and 30 wt %) com-
posites atroom temperature.
 Magnetoelectric properties
• Magnetoelectric properties of the (100-x) BT - xCFO composite
samples are shown in Fig.
• Piezoelectric coefficient (d33), magneto electric voltage and
magnetoelectric coeffiecient values are tabulated in below.
Sample d33 (pC/N) ME voltage (mV) aE (mV/cm-Oe)
90BT-10CFO 29 9.62 0.78
80BT-20CFO 21 18.8 1.29
70BT-30CFO 13 16.9 1.16
Table:-. Piezoelectric strain coefficient(d33) and ME Voltage of (100-x) BT-xCFO composites.
• It was observed that d33 value decreases with increasing content of
ferromagnetic phase and a maximum value of 29 pC/N was
obtained for 90BT- 10CFO.
• It is observed from the figure that ME voltage increases with applied
magnetic field up to a value and but starts decreasing with further
increase of applied magnetic field in the composites.
• Among the composites studied, ME voltage of 18 mV and ME
coefficient value of 1.29 mV/cm-Oe was obtained for 80BT-20CFO,
which was the highest among the samples studied.

29.  Conclusion
• Diphasic composites of BT-CFO were successfully prepared by solid state reaction method.
• XRD peaks observed correspond to both the phases with no impurity peaks
• Morphology of the composites shows that grains of both phases are present in all BT-CFO composites with good density.
• Dielectric and polarization studies show that CFO influence the ferroelectric nature of BT and a separate peak in the
dielectric curve was observed around magnetic Curie temperature of cobalt ferrite
• ME coefficient was obtained and the highest value is obtained for 80BT-20CFO.

30. ME Effect: Influence of magnetic (electric)field
on polarization (magnetization)
Direct ME effect (MEH)
Polarization iscontrolled
by magneticfield
Indirect ME effect (MEE)
Magnetization is
controlled by electricfield
Applied
magneticfield
C. W. Nan, M. I. Bichurin, S. X. Dong, D. Viehland, and G. Srinivasan, J. Appl. Phys. 103, 031101 (2008)
Strain transferred to
piezoelectricphase
Piezoelectric
polarization
Strain generated
due to
magnetostriction
Magnetodielectricphenomenon
30

31. Ferric, cobalt and zinc
nitrate mixed together+
citric acid
Stirred at 80oC till gel
formation
Combustion occurs at
120oC to form ashes
Ground and calcined at
750oC for 5h
sintered at 950oC for
7h
CoZn0.1Fe1.9O4
Stirred at 80oC
till gel formation
Combustion occurs at
120oC to form ashes
Ground and calcined
at 600oC for 1h
sintered at 1250oC for
2h
Pb0.07Yb0.03Zr0.48Ti0.52O3
Pb(NO3)2+ethylene glycol
ytterbium
nitrate+Zr(OC3H7)4+nitric
acid+Ti{OCH(CH3)2}4+ace
tyleacetone
xCMnFO -(1-x)Yb PZT
(x= 0.02, 0.05 and 0.08)
Grinding for 10h
Pellet formation with 5-
10% PVA s binder
Sintered at 800oC for
6h
Multiferroic
composites
designated as
S2, S5, S8
Experimental Plan for Synthesis of ME composite
Sol gel auto combustion
Solid State
rxn method
Ferroelectric phase Ferrite phase
31