11 that the value of ME voltage coef ficient decreases with increasing low magnetic fields and attains a constant value in high magnetic fields, which might be due to the presence of strain[r]
Trang 1Original Article
Dielectric, magnetic and magnetoelectric studies of lithium ferrite
synthesized by solid state technique for wave propagation
applications
a Department of Physics, GEBH, Sree Vidyanikethan Engineering College, Tirupati 517102, A.P., India
b Department of Chemistry, GEBH, Sree Vidyanikethan Engineering college, Tirupati 517102, A.P., India
c Department of Physics, Andhra University, Visakhapatnam 530 003, A.P., India
d Department of Physics, GIT, GITAM University, Visakhapatnam 530 045, A.P., India
a r t i c l e i n f o
Article history:
Received 14 March 2018
Received in revised form
21 April 2018
Accepted 22 April 2018
Available online 28 April 2018
Keywords:
Li 0.5 Fe 2.5 O 4
XRD
Dielectric constant
Impedance spectroscopy
Magnetic transition temperature
ME coefficient
a b s t r a c t
The electric and magnetic properties of a lithium ferrite (LF) synthesized using the solid state reaction technique have been reported The XRD studies reveal the cubic nature, from which the crystallite size and the lattice constant are determined to be 16.84 nm and 2.847Å repectively The FESEM confirms the coarseness in the samples with a low porosity Variations of the dielectric constant and dielectric loss with temperature at different frequencies have been studied The dielectric constant increases more steeply in the negative direction with increasing temperature beyond 500C at 100 kHz The impedance plot exhibits almost complete semicircles at all temperatures, whose centers situated on the real axis This suggests that the sample obeys the Debye behavior The magnetic studies reveal a soft magnetic characteristic of LF The ME voltage coefficient decreases with increasing magnetic field and attains a constant value in the high magneticfield
© 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
1 Introduction
Magnetic spinel ferrites have encapsulated the global market
and seized the awareness of many researchers due to their
enchanting and tropical electromagnetic properties [1] Due to a
wide range of applications, the lithium ferrite (LF: Li0.5Fe2.5O4) is
considered to be one of the mostflexible ferrites The LF belongs to
the group of soft materials and has potential applications such as
computer memory chips, microwave devices, magnetic recording
media, transformer cores rod antennas, radio frequency coil
fabri-cation, many branches of telecommunifabri-cation, electronic
engineer-ing[2e6], in the information storage, switching devices and phase
shifters because of their excellent rectangular hysteresis loop
characteristics [7] At room temperature, the LF exhibites high
permeability and high saturation magnetization Thus, it is
considered a highly potential material for applications from low to microwave frequencies
In microwave frequencies, the LF is a useful material due to its high resistivity semiconductor, and low eddy-current losses[8,9] The electrical properties of LFs depend on the method of the preparation, its grain size, chemical composition and sintering temperature[10e12] Besides the high resistivity, the LF can work
in high frequency devices thanks to its mechanical hardness, square loop properties and high Curie temperature[13,14] Indeed, the LF material has the highest Curie temperature of 670C among all ferrimagnetic oxides[15] It is used in computer core industry[16] The high ratios of anisotropy to magnetostriction in the LF result in
a lower stress-sensitivity of the remanence Depending on the distribution of lithium and iron ions in octahedral sites (B-sites) and the sintering temperature, the structure of the LF changes from the ordered phase (a) to the disordered phase (b)[17] Many research groups[18e21]have focused their attention on the synthesis of the
LF because this material exhibited a positive dielectric constant A material exhibiting negative dielectric constant can be used in the application like wave propagation, electrolyte behavior, and bio-membrane functions [22] Also, materials having very low
* Corresponding author.
E-mail address: ganapathi.gajula@gmail.com (G.R Gajula).
Peer review under responsibility of Vietnam National University, Hanoi.
Contents lists available atScienceDirect Journal of Science: Advanced Materials and Devices
j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d
https://doi.org/10.1016/j.jsamd.2018.04.007
2468-2179/© 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license
Trang 2The compounds used for the preparation of LF are Li2CO3(99%, Loba
Chemie), Fe2O3(98%, Loba Chemie) The Li2CO3and Fe2O3powders
were ground together using an agate mortor The grinding process
was carried out for 10 h to obtain a homogeneous mixture and
distribution of the ingredients The sample was calcinated at 800C
for 3 h After completion of the calcination process, the powder was
again ground for 3 h and then added Poly Vinyl Alcohol to the
calcinated powder and grinded up to become afine powder A die
set of 10 mm diameter was used to transform powder into pellets
The powder was placed on a die set and pressed by applying a
pressure of 5 tonnes for 3 min using a hydraulic press The strength
of these pellets was increased by a sintering process at a
temper-ature of 900C for 3 h The XRD measurements were carried out
using Bruker D8 Advance X-Ray Diffractometer, FESEM with energy
dispersive analysis of X-ray (EDAX) for morphology and
quantita-tive elemental analysis of a sample was analyzed by Carlzeiss
ultra-55 The dielectric measurements were obtained from LCR Meter,
Wayne Kerr Electronics Pvt Ltd., Model: 1J43100 The variation of
magnetization with temperature (MT) of the samples was
measured by Vibrating Sample Magnetometer (VSM) Quantum
Design PPMS, Model 6000 and the magneto-electric voltage
coef-ficient (aME) was measured with respect to the DC magneticfield
(Hdc) by superimposing 1 Oe AC magnetic field generated by
Helmholtz coils at a frequency of 1 kHz The output voltage of the
composite was measured using SR 830 DSP lock-in amplifier We
have characterized these sintered pellets, which will be discussed
in the forthcoming sections
3 Results and discussion
3.1 X-ray diffraction
The XRD pattern of the LF is shown inFig 1 We have indexed the
diffraction peaks of LF using JCPDS no 89-7832& 88-06711 The
XRD pattern of LF reveals the formation of a spinel cubic structure
[20] The extra peaks pertaining to the impurities are not observed,
which strongly confirm the high crystalline nature of the sample
The lattice parameter of the LF has been calculated using
a¼ dhklpffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffih2þ k2þ l2
(1)
The lattice parameter of the LF is 8.247Å, which is equal to the
earlier reported value[25] The average crystallites size of the LF
has been calculated using Scherrer's relation
It turns out that the average crystallite size of the LF is 16.84 nm
3.2 Morphological studies The EDAX spectrum and SEM micrograph of the LF are shown in Fig 2(a) and (b), respectively.Fig 2(a) confirms the presence of elements Fe and O but Li element cannot be identified by the in-strument due to its low atomic number
Fig 2(b) shows that micrograph exhibits clear grains and clear grain boundaries with small pores The average grain size of the LF calculated using ImageJ software is 6.2491mm The SEM confirms the coarseness in the sample with low porosity The larger grains observed here are due to an agglomeration of smaller grains These larger uneven grains can show important differences in calculating the polarization or the ME effect[26]
3.3 Dielectric studies 3.3.1 Temperature dependence of the dielectric constant The temperature dependence of the dielectric constant (3 0) of
the LF at different frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz and
10 MHz) is shown inFig 3 FromFig 3, it is clearly seen that the dielectric constant increases up to 550C for all samples Beyond this temperature, the dielectric constant decreases with increasing the temperature A kink is observed at 550 C The nature of variation of dielectric constant with temperature at all frequencies except 1 kHz is same till 500C Also, in this temperature range, the dielectric constant of the LF decreases with an increase in the frequency The dielectric constant becomes negative and increases
in the negative direction beyond 600C and 500C temperatures for the frequencies of 10 kHz and 100 kHz, respectively For the frequencies of 1 MHz, 10 MHz, the material exhibits small negative dielectric constant beyond the temperature 600C This may be due to the dimensional resonance, domain resonance, irregular grain boundaries In this case, the domain walls reduce dipole charges and then produce negative charges at high frequencies beyond a certain high temperature At the frequency of 1 kHz, the dielectric constant shows a jumping behavior around 650C As can be seen below, this may relate to the steep decrease of the dielectric lossFig 4, however, it may also be connected to instru-mental errors Note that, the negative dielectric constant was successfully explained by Jones et al.[27] According to Jones et al., during relaxation process, holes are added to the material which recombine with free electrons in the dipole This recombination of holes with free electrons reduces the charge of the dipole and hence yields negative values of the dielectric constant Champness and Clark[28]claim that the negative values of dielectric constant arise from the inductive behavior of materials[29]and depend on
Fig 1 X-ray diffraction pattern of the synthesized LF.
Trang 3the penetration of minority carriers Moreover, Martens et al.[30]
proposed a model based on the space charge carrier and the
Poisson equation to explain the negative dielectric constant effect,
caused by the distribution of relaxation times The materials with
negative dielectric constant have attracted many research groups
due to their applications in wave propagation, electrolyte behavior,
and bio-membrane functions[22]
3.3.2 Temperature dependence of the dielectric loss
The variation of the dielectric loss (tand) with temperature at
different frequencies is shown inFig 4 It is clearly seen from this
figure that, initially, the dielectric loss of the LF increases slightly
with increasing the temperature at all frequencies At 1 kHz, the
dielectric loss increases with increase in the temperature till 600C
Beyond 600C, the dielectric loss reaches the maximum and then
decreases steeply with increasing the temperature At the
fre-quency of 10 kHz, a similar behaviour is observed beyond 510C
Here, however, the dielectric loss suddenly decreases to zero and
then shows a negative dielectric loss with a minimum at 540C It is
also seen from Fig 4that the behavior of dielectric loss at
fre-quencies of 100 kHz, 1 MHz, 10 MHz is similar to that observed at
10 kHz, but with the much lower magnitudes As the frequency
increases from 1 kHz to 1 MHz, the dielectric loss of the LF
decreases which reaches a minimum value at 10 MHz This is considered to be caused by the domain wall resonance
3.3.3 Frequency dependence of the dielectric constant The variation of dielectric constant of the LF with frequency at different temperatures is shown inFig 5 We see fromFig 5that at
30C, the dielectric constant decreases with increase in frequency
up to 12.76 kHz, beyond that frequency, the dielectric constant reaches constant Also, we see fromFig 5that the dielectric con-stant of the LF exhibits a tendency to increase with increasing temperature Hence, at low frequency region, the dielectric con-stant of the LF shows the dispersion at all temperatures The observed behaviour of the dielectric constant can be explained on the basis of Koops theory[31] According to Koops theory, a high conducting grain is surrounded by non-conducting grain bound-aries The grain boundaries are more effective at low frequencies than grains and grains are more effective at higher frequencies than grain boundaries Due to the large resistance of grain boundaries, the charge carriers produce space charge polarization As a result, the dielectric constant is larger at low frequency region [32] Furthermore, increasing the frequency, the charge carriers change their direction of motion due to the fact that this accumulation of charge at the grain boundary decreases which results in the decrease of dielectric constant The dielectric constant increases with increasing temperature in the low frequency region due to an
Fig 2 (a) EDAX spectrum, (b) FESEM micrograph of the LF.
Fig 3 Temperature dependence of the dielectric constant at frequencies of 1 kHz,
10 kHz, 100 kHz, 1 MHz and 10 MHz for the LF.
Fig 4 Temperature dependence of the dielectric loss at different frequencies of the LF.
Trang 4exchange of electron between Fe2þand Fe3þions at octahedral sites
is thermally activated[32]
3.3.4 Frequency dependence of the dielectric loss
The variation of dielectric loss (tand) of the LF with frequency at
different temperatures is shown inFig 6 We see fromFig 6that
the dielectric loss of the LF decreases with increase in frequency at
all temperatures up to 12.76 kHz, beyond that frequency the
dielectric loss reaches constant at all temperatures And also we see
fromFig 6that the dielectric loss of LF is high in the low frequency
region at all temperatures and at low frequency region the
dielec-tric constant increases with increasing temperature At low
fre-quency region, the dielectric loss of the LF exhibits dispersion
between temperatures, the dielectric loss trend follows as a
dielectric constant curve The dielectric loss is almost constant for
the frequency at low temperatures, which might be due to the
inability of the electric dipoles to respond to an applied electric
field The LF ceramic could present an increased conductivity as
well as an increased dielectric loss at low frequencies[33,34]
3.4 Impedance studies
3.4.1 Temperature dependence of the impedance
The variation of impedance (Z0) of the LF with temperature from
30C to 700C at different frequencies of 1 kHz, 10 kHz, 100 kHz,
1 MHz and 10 MHz is shown in Fig 7 At 1 kHz frequency, the
impedance increases with increasing temperature, reaches the maximum at 132 C Beyond this temperature, the impedance sharply decreases with increasing temperature till 300 C After that, the impedance (Z0) attains a constant value We also see from Fig 7that the impedance of the LF material decreases with increase
in frequency and attains minimum value for frequencies of 10 kHz and 100 kHz The decrease in impedance at higher frequencies may
be attributed to the hopping of electrons between localized ions [35]and the accumulation of charges at grain boundaries[36] 3.4.2 Frequency dependence of the impedance
The variation of impedance (Z0) with frequency at different temperatures of the LF is shown inFig 8 Thefigure clearly shows that the impedance is rather high at low frequencies at 30 C temperature The impedance decreases monotonically with increasing frequency up to 25 Hz, beyond that frequency, the impedance reaches constant At higher temperatures, the ampli-tude of Z0 is strongly supressed However, a similar frequency dependence is still observed This behaviour suggests the presence
of space charges which leads to a slow dynamic relaxation process [37] The constant value of the impedance, however, is a conse-quence of the creation of space charges as a result of which the barrier in the ceramic sample is lowered[38,39]
3.5 Nyquist plots Fig 9shows the plot between the real and imaginary parts of complex impedance Z0 and Z00 at various temperatures of the LF
Fig 5 Frequency dependence of the dielectric constant at different temperatures of
the LF.
Fig 7 Variation of the impedance with temperature at different frequencies of the LF.
Trang 5From the nature of the plot we confirm that the behavior of the
impedance plot obeys the ColeeCole formula[40] The impedance
plot exhibits good semicircles All the semicircles are complete at all
temperatures Moreover, all the semicircles have their centers
sit-uated on the real axis, which suggests that the sample obeys Debye
behavior[41] We see fromFig 9 that semicircular arc shifts
to-wards the origin as temperature increases This implies that the
resistivity of the sample decreases and the mobile ion has a
sur-faced electrode effect at higher temperatures Hence the
conduc-tivity of the LF increases with increasing temperature As
temperature increases, the area under the curve decreases
3.6 Magnetic properties
3.6.1 MeH loop
The variation of magnetization with a magnetic field (MeH
loop) of the LF at room temperature is shown inFig 10 It is clearly
seen that the LF exhibits a ferromagnetic behavior The saturation
magnetization, remanent magnetization and coercive field are
64.51 emu/g, 0.48 emu/g and 2.8 Oe, respectively The obtained
saturation magnetization value is very close to the earlier reported
values[42,43] The area of the hysteresis loop is very narrow Also,
retentivity and coercivefield are very small for the LF, suggesting
that the LF is a soft magnetic material[44]so that it can be easily
magnetized and demagnetized A soft magnetic material is used to
make temporary magnets and also used in transformer cores,
magnetic switching circuits and magnetic amplifiers, etc Hence, the LF can be used in the above-mentioned applications
3.6.2 Magnetoelectric voltage coefficient The variation of ME voltage coefficient with the magnetic field of
LF is shown inFig 11 We see fromFig 11that the value of ME voltage coefficient decreases with increasing low magnetic fields and attains a constant value in high magneticfields, which might be due to the presence of strain in magnetic domains [18] The maximum value of the ME voltage coefficient is 25 mV cm1Oe1at
the lowest applied magnetic field, which is very much small as compared with Ni-based Metglas/PZT laminates and (Fe90Co10)78
-Si12B10-AlN thinfilm by Greve et al.[45]and Huong Giang et al.[46] Any material exhibing large ME voltage coefficients at low magnetic fields and high dielectric loss shall be used in sensor applications[45e47]
4 Conclusion The LF was successfully synthesized using the convention solid state technique The compound was formed in the spinel cubic structure with the lattice parameter of 8.247Å The porosity in the sample was rather low At some frequencies, the negative dielectric constant increases with increasing temperature due to a distribution
of relaxation times The dielectric constant of the LF gets a high value
at low frequencies and at room temperature The dielectric constant decreases with increasing frequency The dielectric constant attains constant at the high frequency region The dielectric loss of the LF is high in the low frequency region at all temperatures and at the low frequency region the dielectric constant increases with increasing temperature At frequencies of 100 kHz, 1 MHz and 10 MHz, the variation of the impedance with temperature is very small The impedance plot obeys the ColeeCole formula, and the semicircular arc shifts towards the origin as temperature increases The reten-tivity and the coercivefield of the LF are very small, which suggest that the LF is a soft magnetic material The ME voltage coefficient decreases with increasing magnetic field and attains a constant value in a high magneticfield Thus, the LF material has rather low
ME voltage coefficient and high dielectric loss This material exhibits high potential for applications like wave propagation, electrolyte behavior, bio-membrane functions and sensing devices
Acknowledgments
We thank Dr P.D Babu for extending his MeH measurements of UGC-DAE Consortium for Scientific Research, Mumbai center,
R5-Fig 9 Variation of the real and imaginary parts of the impedance at different
temper-atures for the LF.
Fig 10 Magnetic hysteresis loop (M-H) taken at room temperature for the LF.
Fig 11 Variation of the magnetoelectric voltage coefficient with magnetic field for the LF.
Trang 6R Sasikala, Investigation of structural and magnetic properties of
nano-crystalline manganese substituted lithium ferrites, J Solid State Chem 182
(2009) 3217e3221
[6] Vivek Verma, M Abdullah dar, Vibhav Pandey, Anterpreet Singh,
S Annapoorni, R.K Kotnala, Magnetic properties of nano-crystalline
Li 0.35 Cd 0.3 Fe 2.35 O 4 ferrite prepared by modified citrate precursor method,
Mater Chem Phys 122 (1) (2010) 133e137
[7] R.G Kharabe, S.A Jadhav, A.M Shaikh, D.R Patil, B.K Chougule, Magnetic
properties of mixed LieNieCd ferrites, Mater Chem Phys 72 (2001) 77e80
[8] S.A Mazen, F Metawe, S.F Mansour, IR absorption and dielectric properties of
LieTi ferrite, J Phys D Appl Phys 30 (1997) 1799e1808
[9] D.H Ridgley, H Lensoff, H.D Childress, Effects of lithium and oxygen losses on
magnetic and crystallographic properties of spinel lithium ferrite, J Am.
Ceram Soc 53 (6) (1970) 304
[10] M.A El Hiti, Dielectric behavior and ac electrical conductivity of
Zn-substituted NieMg ferrites, J Magn Magn Mater 164 (1e2) (1996) 187e196
[11] P.V Reddy, R Sathyanarayana, T.S Rao, Electrical conduction in nickel ferrite,
Phys Status Solidi A 78 (1983) 109e111
[12] A Verma, T.C Goyal, R.G Mindiretta, R.G Gupta, High-resistivity nickelezinc
ferrites by the citrate precursor method, J Magn Magn Mater 192 (2) (1999)
271e276
[13] A Tomas, P Laruelle, J.L Dormann, M Nogues, Affinement de la structure des
formes ordonnee et desordonnee de l'octaoxopentaferrate de lithium, LiFe5O8,
Acta Crystallogr Sect C Cryst Struct Commun 39 (12) (1983) 1615e1617
[14] Seema Verma, P.A Joy, Magnetic properties of superparamagnetic lithium
ferrite nanoparticles, J Appl Phys 98 (12) (2005) 124312e124319
[15] J Smit, H.P.J Wijn, Ferrites, John Wiley and Sons, 1959
[16] A.P Greifer, Ferrite memory materials, IEEE Trans Magn 5 (4) (1969)
774e811
[17] I Mirza Bichurin, M Ulandimir Petrov, Composite magnetoelectrics: their
microwave properties, Ferroelectrics 162 (1) (1994) 33
[18] Yen-Pei Fu, Microwave-induced combustion synthesis of Li 0.5 Fe2.5xCr x O 4
powder and their characterization, Mater Res Bull 41 (2006) 809e816
[19] G Aravind, Abdul Gaffoor, D Ravinder, V Nathanial, Impact of transition
metal ion doping on electrical properties of lithium ferrite nanomaterials
prepared by auto combustion method, Adv Mater Lett 6 (2) (2015) 179e185
[20] Maheshkumar L Mane, R Sundar, K Ranganathan, S.M Oak, K.M Jadhav,
Effects of Nd:YAG laser irradiation on structural and magnetic properties of
Li 0.5 Fe 2.5 O 4 , Nucl Instrum Method Phys Res B 269 (2011) 466e471
[21] Mathew George, Swapna S Nair, Asha Mary John, P.A Joy, M.R Anantharaman,
Structural, magnetic and electrical properties of the solegel prepared
Li 0.5 Fe 2.5 O 4 fine particles, J Phys D Appl Phys 39 (2006) 900e910
[22] L.M Schoop, L Muchler, C Felser, R.J Cava, Lone pair effect, structural
dis-tortions and potential for superconductivity in Tl perovskites, Inorg Chem 52
(2013) 5479e5483
[23] Manfred Fiebig, Revival of the magnetoelectric effect, J Phys D: Appl Phys 38
(8) (2005) R123eR152
semiconductors at audio frequencies, Phys Rev A 83 (1951) article 121 [32] Mathew George, Swapna S Nair, Asha Mary John, P.A Joy, M.R Anantharaman, Structural, magnetic and electrical properties of the solegel prepared Li 0.5 Fe 2.5 O 4 fine particles, J Phys D Appl Phys 39 (2006) 900e910
[33] H.B Yang, H Wang, F Xiang, X Yao, Microstructure and electromagnetic properties of SrTiO 3 /Ni 0.8 Zn 0.2 Fe 2 O 4 composites by hybrid process, J Am Ceram Soc 92 (9) (2009) 2005e2010
[34] H.B Yang, H Wang, L He, X Yao, Hexagonal BaTiO 3 /Ni 0.8 Zn 0.2 Fe 2 O 4 com-posites with giant dielectric constant and high permeability, Mater Chem Phys 134 (2e3) (2012) 777e782
[35] Z Yan, J.L Huang, Y.J Gu, B Jin, R.Y Wang, Effects of V 2 O 5 addition on the microstructure and microwave dielectric properties of ZnNb 2 O 6 ceramics, Adv Mater Res 476e478 (2012) 940e943
[36] N Padmamalini, K Ambujam, Impedance and modulus spectroscopy of ZrO 2 eTiO 2 eV 2 O 5 nanocomposite, Karbala Int J Modern Sci 2 (2016) 271e275
[37] J Suchanicz, A Je_zowski, R Poprawski, Low-temperature thermal and dielectric properties of Na 0.5 Bi 0.5 TiO 3 , Phys Status Solidi A 169 (1998) 209 [38] R Archana Shukla, N.P Choudhary, Impedance and modulus spectroscopy characterization of La3þ/Mn4þmodified PbTiO 3 nano ceramics, Curr Appl Phys 11 (2011) 414
[39] L Lily, K Kumari, K Prasad, R.N.P Choudhary, Impedance spectroscopy of (Na 0.5 Bi 0.5 )(Zr 0.25 Ti 0.75 )O 3 lead-free ceramic, J Alloys Compd 453 (2008) 325 [40] S Li, W Yang, M Chen, J Gao, J Kang, Y Qui, Preparation of PbO nanoparticles
by microwave irradiation and their application to Pb (II)-selective electrode based on cellulose acetate, Mater Chem Phys 90 (2e3) (2005) 262 [41] E Barsoukov, J Ross Macdonald (Eds.), Impedance Spectroscopy, Theory and Applications, John Wiley, New York, 2005
[42] N Jovic, B Antic, G.F Goya, V Spasojevic, Magnetic properties of lithium ferrite nanoparticles with a core/shell structure, Curr Nanosci 8 (5) (2012) 1e8
[43] S Verma, P.A Joy, S Verma, P.A Joy, Magnetic properties of super-paramagnetic lithium ferrite nanoparticles, J Appl Phys 98 (124312) (2005) 1e9
[44] M.J Miah, M.N.I Khan, A.K.M Akther Hossain, Synthesis and enhancement of multiferroic properties of (x)Ba 0.95 Sr 0.05 TiO 3 e(1x)BiFe 0.90 Dy 0.10 O 3 ceramics,
J Magn Magn Mater 397 (2016) 39e50 [45] H Greve, E Woltermann, H.-J Quenzer, B Wagner, E Quandt, Giant magneto-electric coefficients in (Fe 90 Co 10 ) 78 Si 12 B 10 -AlN thin film composites, Appl Phys Lett 96 (2010) 182501
[46] D.T Huong Giang, P.A Duc, N.T Ngoc, N.H Duc, Geomagnetic sensors based
on Metglas/PZT laminates, Sensor Actuators A 179 (2012) 78e82 [47] Yaojin Wang, Jiefang Li, D Viehland, Magnetoelectrics for magnetic sensor applications: status, challenges and perspectives, Mater Today 17 (6) (2014) 269e275