DTIC ADA621122: Low-temperature Spin Spray Deposited Ferrite/piezoelectric Thin Film Magnetoelectric Heterostructures with Strong Magnetoelectric Coupling

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4. 1ITLE AND SUBTITLE 5a CONTRACTNUMBER
Low-temperature spin spray deposited ferrite/piezoelectric thin W911NF-09-l-0435
film magnetoelectric heterostructures with strong
5b. GRANT NUMBER
magnetoelectric coupling
5c. PROGRAM ELEMENT NUMBER
611103
6. AUTHORS 5d. PROJECT NUMBER
Z. Zhou, 0. Obi, T. X. Nan, S. Beguhn, J. Lou, X. Yang, Y. Gao, M. Li,
S. Rand, H. Lin, N. X. Sun, G. Esteves, K. Nittala, J. L. Jones, K. 5e. TASK NUMBER
Mahalingam, M. Liu, G. J. Brown
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 8. PERFORMI:N'G ORGANIZATION REPORT
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University ofFioridaOffice ofEngineering
339 WeiI Hall
Gainesville, FL 32611 -6550
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(ES) ARO
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13. SUPPLEMENTARYNOTES
The views, opinions and/or fmdings contained in this report are those of the author(s) and should not contrued as an official Department
of the Anny position, policy or decision, unless so designated by other documentation.
14. ABSTRACT
We report low-temperature spin spray deposited
Fe304/Zn0 thin film microwave magnetic/piezoelectric
magnetoelectric heterostructures. A voltage induced
effective ferromagnetic resonance field of 14 Oe was
realized in Fe304/Zn0 magnetoelectric (ME) heterostructmes.
lrnmn<>r<>rl nr;th mn"t th;n f11m ,.,..,, ,J.,,.,tn,., h<>t<>rn"tnll"'tnr<>"
'-'
15. SUBJECT TERMS
magnetoelectric, diffraction, thin film
16. SECURITY CLASSIF1CAT ION OF: 17. LIMITATION OF 15. NUMBER 19a NAME OF RESPONSIBLE PERSON
a REPORT b. ABSTRACT c. THIS PAGE ABSTRACT OF PAGES Jacob Jones
uu uu uu uu 19b. TELEPHONE NUMBER
919-515-4557
Standard Form 298 (Rev 8/98)
Prescribed by ANSI Std. Z39.18
Report Title
Low-temperature spin spray deposited ferrite/piezoelectric thin film magnetoelectric heterostructures with strong
magnetoelectric coupling
ABSTRACT
We report low-temperature spin spray deposited

Fe3O4/ZnO thin film microwave magnetic/piezoelectric

magnetoelectric heterostructures. A voltage induced

effective ferromagnetic resonance field of 14 Oe was

realized in Fe3O4/ZnO magnetoelectric (ME) heterostructures.

Compared with most thin film magnetoelectric heterostructures

prepared by high temperature ([600 C)

deposition methods, for example, pulsed laser deposition,

molecular beam epitaxy, or sputtering, Fe3O4/ZnO ME

heterostructures have much lower deposition temperature

(\100 C) at a much lower cost and less energy dissipation,

which can be readily integrated in different integrated

circuits.
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Continuation for Block 13
ARO Report Number 54169.48-MS-PCS
Low-temperature spin spray deposited ferrite/pie...
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© 2014 . Published in Journal of Materials Science: Materials in Electronics, Vol. Ed. 0 25, (3) (2014), (, (3). DoD Components
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Approved for public release; distribution is unlimited.
JMaterSci:MaterElectron(2014)25:1188 1192
DOI10.1007/s1085401417077
Low-temperature spin spray deposited ferrite/piezoelectric thin
film magnetoelectric heterostructures with strong magnetoelectric
coupling
Z. Zhou • O. Obi • T. X. Nan • S. Beguhn • J. Lou • X. Yang • Y. Gao •
M. Li • S. Rand • H. Lin • N. X. Sun • G. Esteves • K. Nittala • J. L. Jones •
K. Mahalingam • M. Liu • G. J. Brown
Received:9October2013/Accepted:2January2014/Publishedonline:8January2014
(cid:2)SpringerScience+BusinessMediaNewYork2014
Abstract We report low-temperature spin spray depos- to the strong strain mediated ME coupling between the
ited Fe O /ZnO thin film microwave magnetic/piezoelec- ferro/ferrimagnetic and piezo/ferroelectric phases in ME
3 4
tric magnetoelectric heterostructures. A voltage induced heterostructures. Magnetoelectric heterostructure enables
effective ferromagnetic resonance field of 14 Oe was electricfieldcontrolofmagnetismorviceversa[1 6].The
realized in Fe O /ZnO magnetoelectric (ME) heterostruc- ME coupling in multiferroics has led to different ME
3 4
tures. Compared with most thin film magnetoelectric het- devices, such as picotesla magnetic sensors [7], electric
erostructures prepared by high temperature ([600 (cid:3)C) field tunable RF/microwave magnetic devices [8 11],
deposition methods, for example, pulsed laser deposition, tunableresonators[8],phaseshifters[9],tunableinductors
molecular beam epitaxy, or sputtering, Fe O /ZnO ME [10] and tunable filters [11]. Compared to state of the art
3 4
heterostructures have much lower deposition temperature microwave magnetic devices tuned by magnetic fields, the
(\100 (cid:3)C) at a much lower cost and less energy dissipa- electricfieldorvoltagetunableMEdevicesaremuchmore
tion,whichcanbereadilyintegratedindifferentintegrated energy efficient, lightweight, compact, and less noisy.
circuits. Studies on ME heterostructures are mostly based on
complexoxidepiezoelectricceramicorsinglecrystal,such
as lead zirconate titanate, barium titanate, lead zinc nio-
bate lead titanate (PZN-PT), lead magnesium niobate-
1 Introduction lead titanate, etc. Most of these thin film ME heterostruc-
tures are typically grown by pulsed laser deposition [12],
Layeredmagnetoelectric(ME)heterostructureswithtwoor molecularbeamepitaxy[13],chemicalsolutiondeposition
more constituent phases of ferro/ferrimagnetic and piezo/ [14],sputtering[5,6]orpyrolyzing[15].These deposition
ferroelectricphaseshavegainedalotofrecentinterestdue methods for ME heterostructures require high processing
temperatures of[600 (cid:3)C, which leads to interface diffu-
sion and degraded RF magnetism or piezoelectricity [14].
Z.ZhouandO.Obihavecontributedequallytothiswork. Thehighprocesstemperaturesmakeitverychallengingin
integrating these ME devices onto radio frequency inte-
Z.Zhou(cid:2)O.Obi(cid:2)T.X.Nan(cid:2)S.Beguhn(cid:2)J.Lou(cid:2)X.Yang(cid:2)
Y.Gao(cid:2)M.Li(cid:2)S.Rand(cid:2)H.Lin(cid:2)N.X.Sun(&) gratedcircuitsormonolithicmicrowaveintegratedcircuits.
DepartmentofElectricalandComputerEngineering, Spin-spray deposition method is a unique wet chemical
NortheasternUniversity,Boston,MA02115,USA technique for synthesizing high crystalline quality, low-
email:[email protected]
loss and fully dense RF/microwave complex oxide films.
For example, spinel ferrites thin film can be fabricated
G.Esteves(cid:2)K.Nittala(cid:2)J.L.Jones
DepartmentofMaterialsScienceandEngineering,Universityof directly from aqueous solution at *90 (cid:3)C through this
Florida,Gainesville,FL326116400,USA method. The processing temperature is much lower than
that of ([600 (cid:3)C) other ferrite preparation methods [16
K.Mahalingam(cid:2)M.Liu(cid:2)G.J.Brown
18].Inaddition,tightatomicbondingcanbeformedatthe
MaterialsandManufacturingDirectorate,AirForceResearch
Laboratory,WrightPatterson,AFB,OH454337707,USA interface between spin-spray synthesized ferrite films and
1 3
JMaterSci:MaterElectron(2014)25:1188 1192 1189
ferroelectrics, with minimal interface inter-diffusion, crystallographic texture of the thin film Fe O (1.4 lm)/
3 4
which leads to strong ME coupling and thereby provides ZnO (3 lm) heterostructure was further investigated via
great opportunities for ME heterostructures. Using this XRDatbeam-line11-ID-CoftheAdvancedPhotonSource
method, a giant electric field induced effective magnetic [19 21] using an X-ray wavelength of k = 0.10804 A˚.
fieldof860OehasbeendemonstratedinaFe O /PZN-PT Static ME coupling of thin films Fe O /ZnO ME hetero-
3 4 3 4
magnetic thin film/piezoelectric slab heterostructures [16]. structures was investigated by electric-field induced chan-
Although spin spray deposition of ferrite films has been ges in a vibrating sample magnetometer (VSM).
widely performed [16], the spin spray deposition of ferro- Piezoelectric coefficient of ZnO film was obtained by a
electrics or piezoelectrics is rarely explored, except for a photonic sensor. Microwave ME coupling of thin films
recent demonstration of a spin spray deposited ZnO films Fe O /ZnO heterostructures was carried out by custom-
3 4
[17, 18]. ZnO is a typical piezoelectric material, which made microwave FMR spectrometer.
makesitagoodcandidateforthinfilmMEheterostructures
at low temperatures. ZnO is also a direct wide band gap
semiconductor with excellent electrical and optical prop- 3 Results and discussion
erties which makes it applicable in a wide variety of
electron, optoelectronic, spintronics and nanodevices [17, 3.1 Characterization of Fe O /ZnO thin films
3 4
18]. The piezoelectric properties of spin spray deposited heterostructure
ZnO films when combined with spin spray deposited fer-
rites offer a unique opportunity for low-temperature syn- Figure 1a shows the XRD patterns of Fe O /ZnO hetero-
3 4
thesized ferrite/ZnO ME heterostructures, and novel structure. A clear polycrystalline spinel ferrite phase and a
integrated voltage tunable RF/microwave ME devices. typical ZnO wurtzite structure with no strong preferred
In this communication, we demonstrate ME ferrite/pie- orientation is apparent in the Fe O and ZnO films. Fig-
3 4
zoelectric thin film heterostructures of Fe O (1.4 lm)/ ure 1b is an EFTEM image showing the ZnO/Fe O
3 4 3 4
ZnO(3 lm)fabricatedbythespin-sprayprocessonaglass structure in cross-section. The EFTEM imaging was per-
substrate. A clean interface with negligible inter-diffusion formedbasedonthethree-windowtechnique[22].Thisisa
betweenFe O andZnOlayerswasobtainedfromthelow- composite(RGB)imageconstructedbysuperimposingtwo
3 4
temperature deposition, which led to a tight interface independent maps of Fe (green) and Zn (red) distribution
bonding and strong ME coupling. This is in sharp contrast across the whole structure. A sharp boundary distinguish-
to other ME heterostructures deposited by other high- ing the two layers isevident, indicating insignificant inter-
temperature deposition methods above [5, 6, 12 15]. diffusion at the interface. This is also supported by further
Strong static and microwave ME interactions were examination of this region by high-resolution transmission
observed in the Fe O /ZnO ME heterostructure. A large electron microscopy, shown in Fig. 1c, which reveals the
3 4
voltage induced effective magnetic field of 14 Oe was presence of an abrupt and well defined interface between
observed through voltage induced in-plane ferromagnetic the ZnO and Fe O layers.
3 4
resonance (FMR) field shift in the Fe O /ZnO hetero- The crystallographic texture of the thin film Fe O
3 4 3 4
structures. Compared to the high process temperature (1.4 lm)/ZnO (3 lm) heterostructure was further investi-
of[600 (cid:3)Cinvolvedinthedepositionprocessofthesethin gated via XRD at beam-line 11-ID-C of the Advanced
film heterostructures [12, 13], this low temperature spin- Photon Source [19 21] using an X-ray wavelength of
spray processing fabricated ME heterostructures provide a k = 0.10804 A˚. The measured diffraction image is shown
viable route to integration of complex oxide thin film ME in Fig. 2a and a 2h section is extracted from 2.1(cid:3) to 6.2(cid:3)
structures on integrated circuits. over the azimuthal angle from 0(cid:3) to 180(cid:3) and shown in
Fig. 2b. The positions of the ZnO, Fe O and copper dif-
3 4
fraction intensities are also indicated at the top of Fig. 2b
2 Experiment for complete phase identification. The ZnO (10.0) diffrac-
tion intensities are observed at the lowest 2h position
Fe O (1.4 lm)/ZnO (3 lm) magnetoelectric ferrite/pie- (correspondingtoaninter-planardistance,ord,of2.81A˚)
3 4
zoelectric thin film heterostructures fabricated by the spin- and the ZnO (00.2) diffraction intensities are observed at
spray process on a glass substrate (0.2 mm). The Fe O / the next highest 2h position (d = 2.603 A˚). Both ZnO
3 4
ZnO heterostructure composition was confirmed by X-ray (10.0) and (00.2) are non-uniform with azimuthal angle,
diffraction (XRD) patterns using conventional Bragg with the (10.0) intensity being concentrated around azi-
Brentanodiffractiongeometry.Thecross-sectionofFe O / muthal angles of 0(cid:3) and 180(cid:3) (parallel to the plane of the
3 4
ZnO structure was determined by energy-filtered trans- film)andthe(00.2)intensitybeingconcentratedaroundan
mission electron microscope (EFTEM) imaging. The azimuthalangleof90(cid:3)(inthedirectionnormaltothefilm).
1 3
1190 JMaterSci:MaterElectron(2014)25:1188 1192
Fig.1 aXraydiffraction
patternofthespinspray
depositedFe3O4/ZnOthinfilms
MEcomposite;bEnergy
FilteredTEMimageshowing
thezincoxide(red)andiron
oxide(green)layers;cHRTEM
imageoftheironoxide/zinc
oxideinterface(Colorfigure
online)
texture, peak fitting was performed on the (00.h) peak
using the curve fitting toolbox in MATLAB(cid:2) (version
R2011b) and the full width at half maximum of this dif-
fraction peak is determined to be 76(cid:3) ± 4.8(cid:3).
3.2 Static ME coupling measurements of Fe O /ZnO
3 4
heterostructure
Static ME coupling of thin films Fe O /ZnO ME hetero-
3 4
structures was investigated by electric-field induced chan-
ges in a VSM for magnetic hysteresis loops measurements
as shown in Fig. 3a, b. This was done by applying an
external electric-field (E-field) perpendicular to the ZnO
film plane (that is, through the thickness direction). The
Fig.2 a The measured Xray diffraction image using highenergy
E-field applied to the ZnO thin film led to strain/stress in
Xraysintransmissiongeometry;ba2hsectionfrom2.1(cid:3)to6.2(cid:3)over
the azimuthal angle from 0(cid:3) to 180(cid:3); c the distribution of the ZnO the Fe3O4/ZnO heterostructure. Magnetization changes
(10.0) and (00.2) diffraction intensities over the azimuthal angle of were created by the electric-field induced strain due to the
thedetectorwereextractedandarepresented
inverse magneto-elastic effect. Therefore, electric-field
tuning of magnetization can be realized in the ME het-
The distribution of the ZnO (10.0) and (00.2) diffraction erostructure composites through the strain/stress mediated
intensities over the azimuthal angle of the detector were ME coupling.
extracted and are presented in Fig. 2c. These intensity Figure 3ashowsthemagnetichysteresisunderdifferent
distributions indicate that the ZnO film is 00.h-type fiber voltagesfrom-20to20 V,correspondingto ± 67 kV/cm
textured. To quantify the strength of the ZnO (00.h) electric field (E-field), applied across the thickness
1 3
JMaterSci:MaterElectron(2014)25:1188 1192 1191
Fig.3 aInplanemagnetic
hysteresisloopsoftheFe3O4/
ZnOMEheterostructureunder
differentelectricvoltages.
bOutofplanemagnetic
hysteresisloopsoftheFe3O4/
ZnOMEheterostructure.The
enlargedMEcoupling
hysteresisloopshiftisshownon
upperleftinsetonbothfigures
wherejiscurvature,A = Y /Y ,B = t /t ,Y istheYoung’s
S P S P S
modulusoftheglasssubstratelayer(Y = 48GPa),Y isthe
S P
Young’smodulusofZnOpiezoelectriclayer(Y = 17GPa),
P
tS the thickness of the glass substrate layer (t = 0.2 mm)
S
andtPthethicknessofthepiezoelectriclayer(Electricfield
E wasappliedalongZnOthicknessdirection.Thesample
3
wascutintolengthL = 2 cm,widthof0.5 cm.Byusinga
photonicsensor,smalldisplacementdcanbemeasuredfor
determiningsubstratebendingquantitatively.Furthermore,
as shown on Fig. 4a,we can calculate piezoelectric coeffi-
cientd throughtherelationshipofd(E).FromEq.(1),we
31
get the measured d of the ZnO thin film, as shown in
31
Fig.4 a Piezoelectric coefficient measurements of ZnO thin film; Fig. 4b, fitted by red curve, in the Fe3O4/ZnO ME hetero-
belectric fielddependence oftheinplanefieldsweepFMRspectra structure is -4.4 pC/N, which is close to theory value of
oftheFe3O4/ZnOMEheterostructuremeasuredat9.3GHz.Thezero
-5.0pC/N[17,18].
crosspartwas enlargedtodemonstrate aclear MEcouplingshift at
bottomrightinset;cXbandinplaneferromagneticresonance(FMR)
field oftheFe3O4/ZnO heterostructure measured at varyingapplied 3.3 Microwave ME coupling measurements of Fe3O4/
voltagesacrosstheZnOlayer ZnO heterostructure
directionoftheZnOlayer,whichisaboutDM/M = 6.5 % Microwave ME interactions and magnetic tunabilities of
under a constant bias field of 100 Oe. The electric field the Fe3O4/ZnO multilayer were demonstrated by electro-
inducedmagnetizationchangeissmallduetothesubstrate static-field-induced in-plane FMR field changes at room
clamping effect, thin thickness of the ZnO (3.0 lm) and temperature, as shown in Fig. 4a. Here, a custom-made
small piezoelectric coefficient of ZnO, d = 10.1 pC/N, microwave FMR spectrometer using a planar transmission
33
d = -5.0pC/N,[18]whichleadtoarelativelysmallME line was used to perform the FMR measurements of the
31
coupling coefficient. Figure 3b demonstrated out-of-plane ferrite/ferroelectric ME thin films composites at X-band
magnetic hysteresis under different electric field induced (9.3 GHz). In Fig. 4a, the bias magnetic field, was applied
ME coupling, which indicated DM/M = 1.9 % at a bias in the Fe3O4/ZnO film plane with in-plane the microwave
field of 840 Oe. RFfieldandwasperpendiculartotheDCbiasfield.Aclear
Piezoelectric coefficient of ZnO film was obtained by electric field induced effective magnetic field 14 Oe, cor-
measuring the substrate bending effect[23].Uponapplying respondingly,wasobservedbetweenabiasvoltageof-20
anelectricfield,substratebendingcanbeanticipatedinZnO/ and 20 V, which is indicated by the electric field induced
glassheterostructure.Assumingonesideofthespecimenis FMR field change, as shown in bottom right inset of
fixed,thebendingdisplacementdcanbecalculatedas[23]: Fig. 4b. Figure 4c shows the FMR field dependence of
applied voltage from -30 to 30 V. The FMR field varies
1 L2 6ABð1þBÞ
d¼ jL2 ¼ (cid:2)d E linearly as applied voltage switches from -20 to 20 V,
2 2t A2B4þ2Að2Bþ3B2þ2B3Þþ1 31 3
p indicating the piezoelectric property of ZnO thin film. The
ð1Þ FMR field, however, saturates as applied voltage is larger
1 3
1192 JMaterSci:MaterElectron(2014)25:1188 1192
than 20 V, this result accords with the piezoelectric mea- 13].Thisworkpavedthewayforpotentialmultifunctional
surement of ZnO in Fig. 4a, where the displacement of ZnO-based E-field tuning microwave/RF devices.
ZnO/glass substrate linearly increases as applied voltage
from 0 to 23 V, however, saturated around 23 V. This Acknowledgments This work is financially supported by NSF
CAREERawards0746810andbytheUnitedStatesAirForceResearch
phenomenon is reasonable because the FMR field won’t
LaboratoryundercontractnumberFA872105C0002.J.J.,K.N.,and
increasetoinfiniteasappliedvoltage increase.TheFe O /
3 4 G.E. acknowledge support from the Army Research Office through
ZnOheterostructure,canbeconsideredascapacitance,has contract number W911NF0910435. Use of the Advanced Photon
breakdownvoltagelimit,whichis23 Vinourexperiment. Source, an Office of Science User Facility operated for the U.S.
DepartmentofEnergy(DOE)OfficeofSciencebyArgonneNational
This electric-field-induced FMR field change can be
Laboratory,wassupportedbytheU.S.DOEunderContractNo.DE
explainedbythestrain-mediatedelectrostatic-field-induced
AC0206CH11357.
magnetic anisotropy field H . The E-field applied across
eff
ZnO layer can tune the FMR field of Fe O layer up or
3 4
down through strain/stress mediated ME coupling [5, 6], References
seeFig. 4b.Thein-planeFMRfrequencycanbeexpressed
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24. N.Izyumskaya,V.Avrutin,X.Gu,B.Xiao,S.Chevtchenko,J.G.
was shown in thin film heterostructures compared to other
Yoon, H. Morkoc, L. Zhou, D.J. Smith, Appl. Phys. Lett. 91,
thin films ME structure with ME coupling of 5 6 Oe [12, 182906(2007)
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