High-sensitivity laminated magnetoelectric sensors without bias in composite ofpositive/negative giant magnetostrictive materials and piezoelectric single crystalsJitao Zhang, Ping Li, Yumei Wen, Wei He, Jin Yang, Ming Li, Aichao Yang, Caijiang Lu, and Wenli Li

Citation: Journal of Applied Physics 115, 17E517 (2014); doi: 10.1063/1.4865973 View online: http://dx.doi.org/10.1063/1.4865973 View Table of Contents: http://scitation.aip.org/content/aip/journal/jap/115/17?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Giant self-biased magnetoelectric response with obvious hysteresis in layered homogeneous composites ofnegative magnetostrictive material Samfenol and piezoelectric ceramics Appl. Phys. Lett. 103, 202902 (2013); 10.1063/1.4829634 Ring-type electric current sensor based on ring-shaped magnetoelectric laminate of epoxy-bonded Tb 0.3 Dy 0.7Fe 1.92 short-fiber/NdFeB magnet magnetostrictive composite and Pb(Zr, Ti)O 3 piezoelectric ceramic J. Appl. Phys. 107, 09D918 (2010); 10.1063/1.3360349 Strong magnetoelectric charge coupling in stress-biased multilayer-piezoelectricmagnetostrictive composites J. Appl. Phys. 101, 124102 (2007); 10.1063/1.2748712 Push-pull mode magnetostrictive/piezoelectric laminate composite with an enhanced magnetoelectric voltagecoefficient Appl. Phys. Lett. 87, 062502 (2005); 10.1063/1.2007868 Vortex magnetic field sensor based on ring-type magnetoelectric laminate Appl. Phys. Lett. 85, 2307 (2004); 10.1063/1.1791732

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High-sensitivity laminated magnetoelectric sensors without biasin composite of positive/negative giant magnetostrictive materialsand piezoelectric single crystals

Jitao Zhang, Ping Li,a) Yumei Wen, Wei He, Jin Yang, Ming Li, Aichao Yang, Caijiang Lu,and Wenli LiResearch Center of Sensors and Instruments, College of Optoelectronic Engineering, Chongqing University,Chongqing 400044, China

(Presented 5 November 2013; received 22 September 2013; accepted 13 November 2013; published

online 19 February 2014)

Low-frequency and resonance magnetoelectric (ME) responses without bias have been studied in a

three-phase multilayer ME composite consisting of positive/negative giant magnetostrictive

materials (GMMs) Terfenol-D (Tb0.3Dy0.7Fe1.92), Samfenol (SmFe2) plates, and piezoelectric

single crystal 0.67PMN-0.33PT [0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3]. The large intrinsic anisotropic

field with obvious hysteresis and remnant magnetization in SmFe2 plates as well as an exchanging

field induced by the differences in magnetic properties of the two GMMs contributes to the

self-biased ME responses. The experimental results demonstrate that the output sensitivities

without bias for the resonance frequency at 97.5 kHz and the off-resonance frequency at 1 kHz can

reach 1.1 V/Oe and 8.7 mV/Oe, respectively. A step change of ac magnetic field as small as

�2.27� 10�8 T can be clearly distinguished by the amplitude of the output signals under the

resonance frequency of 97.5 kHz. These results provide potential applications for magnetic field

detection without bias by utilizing a multilayer ME laminate due to its self-biased, self-powered,

and ultra-sensitive properties. VC 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4865973]

Multiferroic composites consisting of magnetostrictive

and piezoelectric phases are of interest for studies on strain-

mediated magnetoelectric (ME) effects due to the enormous

potential applications for functional devices such as mag-

netic sensors, energy harvesters, current sensors, microwave

devices, and magnetic random access memories.1–5 The ME

laminates have been studied so far including magnetostric-

tive phases (e.g., ferrites) and piezoelectric phases (e.g., lead

zirconate titanate in various operational modes with different

polarized/magnetized directions.6–9 There are considerable

research activities in recent years on such passive ME mag-

netic sensor with high sensitivities. Previous reports show

that these laminates exhibit a high ac magnetic field sensitiv-

ity of �1 pT at room temperature under resonance condi-

tions.10 Additionally, the magnetic field sensors have been

drawn significant interests for numerous applications, such

as navigation systems, medical sensors, non-destructive ma-

terial testing, and military instruments,11,12 and the ME com-

posites have some excellent performances relative to the

conventional magnetic-sensing devices, including supercon-

ducting quantum interference device (SQUID), Hall sensor,

and fluxgate.13 In order to invoke stronger piezomagnetic

coupling, an additional magnetic field is indispensable for

biasing the GMMs to normally work. Therefore, the stronger

ME coupling for the composite of L-T mode (Longitudinal-

Transverse) can be obtained only at an additional bias of

�400 Oe.14 For the purpose of holding stronger ME coupling

while decreasing the volume, eliminating the requirement

for bias field has become a great interest in its promising

applications to provide a new solution achieving a miniature

self-biased magnetic sensor. Recently, Yang et al. proposed

a bending mode trilayer laminate NKNLS-NZF/Ni/NKNLS-

NZF with its self-biased ME voltage coefficient of

11.78 V�cm�1 Oe�1 at zero bias by utilizing the differences

in magnetic properties of two different magnetostrictive

phases.15 However, challenge still exists in this ME device,

the induced ME voltage at zero bias is too weak to normally

work for field detection in practical applications, and the sen-

sitivity and the signal-to-noise ratio (SNR) of the output volt-

age will decrease correspondingly.

In this study, great efforts have been devoted to maxi-

mizing the self-biased ME coupling by means of intrinsic

anisotropic field in single-phase GMM and bias exchanging

among multiphase GMMs. Compared with the previously

reported self-biased ME solutions, the intrinsic anisotropic

field in SmFe2 plate is much larger than that of most magne-

tostrictive materials due to its huge intrinsic anisotropic con-

stant K1. Therefore, the large intrinsic anisotropic field with

obvious hysteresis in SmFe2 plates as well as a bias exchang-

ing field induced by two different GMM plates contributes to

the self-biased ME responses of the proposed composite.

The total internal field, a superposition of the applied mag-

netization field, and the anisotropic field result in a larger

built-in field and a higher sensitivity induced by the remnant

magnetostriction.

The magnetostrictive materials of Terfenol-D plates are

commercially supplied (Gansu Tianxing Rare Earth

Functional Materials Co., Ltd., China) to have dimensions of

12� 6� 1 mm3 and magnetostrictive crystallographic

axis[110] oriented along the longitudinal direction. SmFe2a)Electronic mail: liping@cqu.edu.cn.

0021-8979/2014/115(17)/17E517/3/$30.00 VC 2014 AIP Publishing LLC115, 17E517-1

JOURNAL OF APPLIED PHYSICS 115, 17E517 (2014)

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(commercially purchased from Baotou Research Institute of

Rare Earths, China), a negative giant magnetostrictive mate-

rial with cubic MgCu2-type structure, large saturation mag-

netostriction coefficient (ks � �1258 ppm at 300 K) and high

Curie temperature (676 K), which has similar dimensions to

the Terfenol-D plates and the easy-magnetized crystallo-

graphic axis[111] oriented along longitudinal direction.16

Piezoelectric single crystal of transversely polarized

0.67PMN-0.33PT [0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3] plate

(Shanghai Institute of Ceramics, Chinese Academy of

Sciences, China) is selected as piezoelectric phase with its

dimensions of 12� 6� 0.8 mm3, which is prepared by a

modified Bridgman technique near the morphotropic phase

boundary (MPB) with [001]-oriented cut. More details about

fabrication and measurement for the sample can be found in

our previously reported literature.4

In principle, the presence of two magnetostrictive mate-

rials can generate a bias exchanging field due to the differ-

ence in their magnetic properties including susceptibility and

coercivity.15 Obviously, in the proposed ME configuration,

this exchanging field induced by the positive/negative

GMMs contributes to the self-biased ME couplings.

Additionally, another internal anisotropic field induced by

the SmFe2 plate also contributes to the self-biased ME

responses. Therefore, the total internal magnetic field inten-

sity Hint in the proposed ME composite origins from two

parts, which can be expressed by Eq. (1)17,18

Hint ¼2K1

l0Ms� KV

l0Ms|fflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflffl}

induced by the twodifferent GMM plates

� 4K1

3l0Ms|fflfflfflfflffl{zfflfflfflfflffl}

induced by the singlephase of SmFe2 plates

; (1)

where K1, KV, Ms, and l0 are the intrinsic anisotropy con-

stant of SmFe2 plate, the exchanging anisotropy constant

between the two GMM plates, the saturation magnetization,

and vacuum permeability constant. KV is defined as a differ-

ence of energy consumption per unit volume for saturation

magnetization required between along [111]-oriented direc-

tion in SmFe2 plates and [110]-oriented direction in

Terfenol-D plates, which reflects the extent of the bias

exchanging. In order to further illustrate the large intrinsic

anisotropy field in SmFe2 materials, the M-H hysteresis

loops for SmFe2 and Terfenol-D samples are measured along

their longitudinal direction, and the results are shown in

Fig. 1. The saturation magnetization (Ms) and the coercive

field (Hc) for SmFe2 are 56.91 emu/g and 329.92 Oe, respec-

tively. Correspondingly, the saturation magnetization and

the coercive field for Terfenol-D samples are 85.921 emu/g

and 21.03 Oe, respectively. The hysteresis and remnant mag-

netization are clearly observed in SmFe2 sample within the

range of �8000 Oe� 8000 Oe, but less hysteresis exists in

Terfenol-D plate. Actually, almost all magnetostrictive mate-

rials have the phenomenon of small hysteresis and remnant

magnetization due to their intrinsic ferromagnetism.

However, hysteresis and remnant magnetization are more

obvious in SmFe2 plates due to its large anisotropy constant

K1 (K1¼�5.3� 106 ergs/cm3 for SmFe2 samples). Therefore,

a large internal field can be provided in single-phase magneto-

strictive materials of SmFe2.

The dependence of av on f at Hbias¼ 0 for this composite

is demonstrated in Fig. 2(a). A giant sharp resonance peak

with value of 1.1 V/Oe is observed at the resonance fre-

quency of 97.5 kHz. Then the measurements of av vs Hbias

are carried out at its resonance conditions of 97.5 kHz for

magnetic field sweeping. Fig. 2(b) illustrates the peak

value of the dependency of the resonant ME voltage coeffi-

cient av on the external magnetic bias, and the obvious phe-

nomenon of non-zero ME response at zero bias is observed.

As Hbias increases from zero, the ME voltage coefficient av

increases with an initial non-zero value of 1.1 V/Oe, and

then rapidly reaches a maximum value of 4.95 V/Oe at

Hbias¼ 235 Oe. Therefore, a self-biased ME voltage coeffi-

cient av of 1.1 V/Oe is obtained from the proposed compos-

ite. The non-zero value of 1.1 V/Oe at zero bias is less than

the maximum av value of 4.5 V/Oe, but more space is

saved due to the removal of the required magnets. According

FIG. 1. The M-H hysteresis loops for Terfenol-D and Samfenol samples.

FIG. 2. (a) The ME voltage coefficient dependence of frequency without

bias. The inset shows schematic diagram of the proposed multilayer ME

composite. (b) Resonant ME voltage coefficient as a function of bias field

for the proposed laminate.

17E517-2 Zhang et al. J. Appl. Phys. 115, 17E517 (2014)

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to the description mentioned previously, this self-biased phe-

nomenon is attributed mainly to the large intrinsic aniso-

tropic field with obvious hysteresis and remnant

magnetization in SmFe2 plate as well as the exchanging field

induced by two different GMM plates.

To evaluate the capabilities of magnetic field detection

for this ME composite without bias, the output sensitivity is

measured at the low frequency of 1 kHz and resonance fre-

quencies of 97.5 kHz. Figure 3 shows the sensitivity of the

induced voltage responding to the variations of magnetic

field strength under zero bias at resonance and off-resonance

conditions. A solenoid with 245 turns is wound around the

composite to carry a small ac voltage provided by lock-in

amplifier with tunable amplitude of the input voltage in the

dynamic range of 0� 1 Vrms. The induced voltage from the

electrode surface of 0.67PMN-0.33PT plate is monitored by

the lock-in amplifier. The experimental results demonstrate

that the induced voltage exhibits an approximately linear

relationship with the input voltage and increases with

the input signal in the initial step change of 0.001 Vrms on

solenoid. The measured sensitivities at resonance and

off-resonance conditions are 1.1 V/Oe and 8.7 mV/Oe,

respectively. Figure 4 plots the output resolution and time

stabilities for the proposed self-biased laminates to small ac

magnetic field variations under the resonance frequency of

97.5 kHz. The small variations of Hac are generated through

a voltage-excited solenoid, and the induced voltages from

the 0.67PMN-0.33PT layer are measured by using the

lock-in amplifier. The output signal goes through a

step-change by adjusting the amplitude of input voltage with

an initial value of 0.001 Vrms. Consequently, it is clear that

the input signal variations as small as 0.001 Vrms (approxi-

mately 2.27� 10�8 T at 97.5 kHz) can be clearly distin-

guished above the noise floor in a time-domain capture

mode.

In summary, a three-phase multilayer ME laminate con-

sisting of positive/negative GMM plates and piezoelectric

single crystal plate have been proposed. Studies on self-

biased ME responses in the proposed laminate show a factor

�1166 higher in output sensitivity at the resonance condi-

tions relative to that in previous reports. This enhancement is

attributed mainly to the large intrinsic anisotropic field with

obvious hysteresis and remnant magnetization in SmFe2

plates as well as an exchanging field induced by the two dif-

ferent GMM plates. In order to further explain this phenom-

enon, the M-H hysteresis loops of Samfenol and Terfenol-D

samples are measured along their longitudinal direction for

comparison. The experimental results demonstrate that the

high sensitivities without bias at the resonance frequency of

97.5 kHz and at the off-resonance frequency of 1 kHz can

reach 1.1 V/Oe and 8.7 mV/Oe, respectively. A small voltage

step change on solenoid of �2.27� 10�8 can be accurately

distinguished by the amplitude of the output voltages. The

ultra-sensitive, self-biased, and self-powered properties of

the proposed miniature ME multilayer composite provide

great potentials for weak magnetic field detection.

This research was supported by the National High

Technology Research and Development Program of China

(863 Program) (No. 2012AA040602) and the National

Natural Science Foundation of China (Grant Nos. 61374217

and 61071042).

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FIG. 3. The sensitivity of the output voltage for the proposed composite at

1 kHz and 97.5 kHz under step changes of ac voltage on solenoid.

FIG. 4. Resolution of the composite without bias in respond to an ac input

magnetic strength variation as small as 2.27� 10�8 T.

17E517-3 Zhang et al. J. Appl. Phys. 115, 17E517 (2014)

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