A method of preparing nonepitaxially grown, highly textured L10 FePt thin films is described. A nearly perfect (001) texture was obtained by direct deposition of FePt films on Corning 7059 glass substrates and subsequent rapid thermal annealing. The ordering and orientation of the L10-phase FePt grains were controlled by the initial as-deposited film structure, and also by the annealing process. Magnetic measurements reveal large perpendicular anisotropy for these (001) textured films. The substrates and processes used for nonepitaxial growth of L10 ordered FePt films are much more compatible with practical applications than those grown epitaxially

Powers, Nathan D.

Sellmyer, David J.

Yan, M.L.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln David Sellmyer Publications Research Papers in Physics and Astronomy 5-15-2003 Highly oriented nonepitaxially grown L10 FePt films M.L. Yan University of Nebraska - Lincoln Nathan D. Powers University of Nebraska-Lincoln, ndp5@byu.edu David J. Sellmyer University of Nebraska-Lincoln, dsellmyer@unl.edu Follow this and additional works at: https://digitalcommons.unl.edu/physicssellmyer  Part of the Physics Commons Yan, M.L.; Powers, Nathan D.; and Sellmyer, David J., "Highly oriented nonepitaxially grown L10 FePt films" (2003). David Sellmyer Publications. 31. https://digitalcommons.unl.edu/physicssellmyer/31 This Article is brought to you for free and open access by the Research Papers in Physics and Astronomy at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in David Sellmyer Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Highly oriented nonepitaxially grown L10 FePt filmsM. L. Yan,a) N. Powers, and D. J. SellmyerCenter for Materials Research and Analysis and Department of Physics and Astronomy,University of Nebraska, Lincoln, Nebraska 68588~Presented on 15 November 2002!A method of preparing nonepitaxially grown, highly texturedL10 FePt thin films is described. Anearly perfect~001! texture was obtained by direct deposition of FePt films on Corning 7059 glasssubstrates and subsequent rapid thermal annealing. The ordering and orientation of theL10-phaseFePt grains were controlled by the initial as-deposited film structure, and also by the annealingprocess. Magnetic measurements reveal large perpendicular anisotropy for these~001! texturedfilms. The substrates and processes used for nonepitaxial growth ofL10 rdered FePt films are muchmore compatible with practical applications than those grown epitaxially. ©2003 AmericanInstitute of Physics.@DOI: 10.1063/1.1556257#I. INTRODUCTIONL10-phase FePt films have attracted much attention forhard and semihard thin-film applications because of theirhigh magnetocrystalline anisotropy constant that promisesthermal stability of material with small grain size. Undernormal growth conditions,L10-phase FePt films often pos-sess~111! preferred or random orientations. In order to con-trol the crystal orientation, epitaxial growth of FePt film wasinvestigated by several deposition techniques includingsputtering1–3 and molecular-beam epitaxy~MBE!.4 The mostcommon methods by which to obtain thec axis normal to thefilm plane @~001! texture# are to use seed or buffer layersbetween a single-crystal substrate, such as MgO, and theFePt thin films. In most cases, however, it is not convenientor practical to use such methods. In the present study, wereport nonepitaxial, highly texturedL10 FePt thin films.~001! texture has been successfully obtained by direct depo-sition of films on glass substrates and subsequent rapid ther-mal annealing~RTA!. The annealing temperature controls or-dering of the FePt grains, and the annealing time controls theorientation of the FePt grains. The orientation mechanism ofFePt films deposited on a glass substrate is totally differentfrom that of epitaxial films. We are able to fabricateL10ordered FePt films in a very short annealing time and controlthe orientation by adjusting the initial as-deposited filmstructures and annealing processes.II. EXPERIMENTThe samples were magnetron sputtered on Corning 7059glass substrates with a multilayer structure of Fe/Pt. Targetsof Fe and Pt were commercial products with purity higherthan 99.9 at. %. The base pressure of the chamber was lessthan 331027 Torr and a working pressure of 4 mTorr Arwas used during sputtering. The substrates were mounted ona water-cooled rotating table. The composition of the filmwas well controlled by adjusting the thickness ratio of the Feand Pt layers. The typical total film thickness was 10 nm.The as-deposited films were annealed by RTA from 350 to650 °C for 2–600 s. The microstructural evolution of thenonepitaxial growth and magnetic properties of these filmswas investigated by x-ray diffraction~XRD!, transmissionelectron microscopy~TEM!, alternating gradient magneto-meter~AGFM! and a superconducting quantum interferencedevice~SQUID!.III. RESULTS AND DISCUSSIONThe ordering and orientation of the FePt films are depen-dent on the annealing temperature and time, and~001! tex-ture is obtained for the film that is less thick. Figure 1 showsthe ordering process of 10 nm FePt film as the annealingtemperature increases, characterized by the increase in inten-sity of the superlattice peaks. FePt films were prepared byFe/Pt multilayer deposition with initial layer thickness of0.47 nm Fe and 0.4 nm Pt. All films were annealed by RTAa!Author to whom correspondence should be address; electronic mail:myan@unlserve.unl.eduFIG. 1. XRD patterns of@Fe (0.47 nm!/Pt (0.4 nm)#12 film annealed at dif-ferent temperaturesTA for 600 s.TA5(a) as deposited and~b! 350,~c! 400,~d! 450, ~e! 500, ~f! 550, and~g! 600 °C.JOURNAL OF APPLIED PHYSICS VOLUME 93, NUMBER 10 15 MAY 200382920021-8979/2003/93(10)/8292/3/$20.00 © 2003 American Institute of PhysicsDownloaded 14 Nov 2006 to 129.93.16.206. Redistribution subject to AIP license or copyright, see http://jap.aip.org/jap/copyright.jspfor 300 s at different temperatures. As can be seen in Fig.1~a!, the film is disordered face-centered-cubic~fcc! phase inthe as-deposited film. When annealing temperatureTA islower than 350 °C@Fig. 1~b!#, the film is still disordered fccphase. AsTA increases to 400–450 °C@Figs. 2~c! and 2~d!#,~001! and ~002! peaks begin to appear, but they are broadand their relative intensity is low, which means that the or-dering process has just started. The overlap of the~200! and~002! peaks means that the film is still a mixture of fcc andface-centered-tetragonal~fct! phases. These results indicatethat the fcc to fct phase transition is incomplete when thesamples are annealed at lower temperature. ForTA above500 °C, the~001! superlattice peak becomes stronger and the~200! and ~002! peaks are separated@Fig. 1~e!#, indicating acompletely ordered phase. We also see that the intensities ofthe ~001! and~002! peaks increase very quickly, whereas theintensity of the~111! peak decreases as the annealing tem-perature increases@Figs. 1~f! and 1~g!#. WhenTA is higherthan 550 °C, the~001! and~002! peaks become dominant andthe ~111! peak has almost disappeared@Fig. 1~g!#, which in-dicates the high degree of~001! texture. This preferential~001! orientation is quite significant since the@001# directionis the easy axis of FePt, and usually FePt films with an easyaxis perpendicular to the film plane can be obtained only byan epitaxial growth technique. Earlier we reported this pref-erential~001! orientation in thinner CoPt,5 FePt:B2O3,6 andCoPt:B2O3 ~Ref. 7! nanocomposite films, and the degree oforientation decreases as the film thickness increases. Thispreferential~001! orientation may be affected by the proper-ties of the interface between the substrate and the FePt mul-tilayers. The first stage of growth of as-deposited films maydetermine the initial nanostructure, and then the orientationof postannealed films.6Figure 2 shows XRD patterns of@Fe ~0.47 nm!/Pt ~0.4 nm!#12 films annealed at 550 °C for different amountsof time. The insets in Fig. 2 are the~001! peak rockingcurves. Superlattice peaks are clearly seen in Fig. 2~a!, indi-cating theL10 ordered structure of FePt grains formed afteronly 2 s of annealing. The broad~001! rocking curve andrelatively higher intensity of the~111! peak indicate de-graded~001! texture and randomly oriented FePt grains. Forthe sample annealed for 600 s, the~001! and~002! peaks aredominant and the~111! peak is almost invisible@Fig. 2~b!#.The rocking curve shows the narrow full width at half maxi-mum ~FWHM! ~55.4°!, which indicates the high degree of~001! texture in the film with a suitable amount of annealing.Our results show that ordering of the FePt grains is verysensitive to annealing temperatureTA , and that orientationof the FePt grains is controlled by the annealing time. Figure3 shows corresponding hysteresis loops of these two samplesmeasured by the SQUID with a field applied either in thefilm plane or perpendicular to the film plane. Almost identi-cal hysteresis loops were measured in both directions for thesample annealed for 2 s@Fig. 3~a!#, which is consistent withrandomly oriented FePt grains. When annealed for 600 s@Fig. 3~b!#, the film exhibits a square perpendicular loop witha high remanence ratio, indicating the development of per-pendicular anisotropy due to preferential~001! orientation.The magnetic measurements are clearly compatible with theXRD results.Another experimental finding is that the orientations ofL10-phase FePt films are also dependent on the initial as-deposited film structure. Figure 4 shows XRD patterns ofFePt films with different bilayer thicknesses. The films wereof the form of (NDFe/NDPt)n , in which DFe was a Fe layerof 0.23 nm, andDPt was Pt layer of 0.2 nm.N was changedfrom 1 to 8 andn ranged from 24 to 3 in order to keep thenominal film thickness around 10 nm. All films were an-nealed by RTA at 550 °C for 5 s. It is clearly seen that thetexture of the film is affected by the initial multilayer struc-ture. Films are~001! textured when the Fe/Pt bilayer thick-ess is small. When the bilayer thickness increases, the rela-tive intensity of the~001! peak decreases and the intensity ofthe~111! peak increases. WhenN increases to 8, the intensityof ~111! increases and becomes dominant. Relatively high~111! intensity and low~001! intensity indicate the develop-ment of ~111! texture. This result shows that the texture ofthe film changed from~001! to ~111! with the increase inbilayer thickness. This preferential~001! texture appears tobe related to the configuration of the nearly monatomic lay-FIG. 2. XRD patterns of@Fe (0.47 nm!/Pt (0.4 nm)#12 film annealed at550 °C for different times:~a! 2 s and~b! 600 s. The insets show the~001!rocking curves.FIG. 3. Hysteresis loops of@Fe (0.47 nm!/Pt (0.4 nm)#12 film annealed at550 °C for~a! 2 s and~b! 600 s. Closed circles represent out of plane loopsand open circles in plane loops.8293J. Appl. Phys., Vol. 93, No. 10, Parts 2 & 3, 15 May 2003 Yan, Powers, and SellmyerDownloaded 14 Nov 2006 to 129.93.16.206. Redistribution subject to AIP license or copyright, see http://jap.aip.org/jap/copyright.jspers. Alternate monatomic-layer deposited FePt films withperpendicular anisotropy deposited at relatively low tem-peratures have been reported.8 In our case, one can see fromFig. 4 that samples comprised of thinner bilayers~in thesecases the layers are only a few atoms thick! acquire a strong~001! texture upon annealing. In these cases the multilayersalready emulate an ordered~001! L10 phase. During subse-quent annealing this requires that the atoms need only moveslightly to obtain a stable fct configuration. This preservesthe orientation prescribed by the multilayer geometry,namely~001!. In the case of the samples with greater bilayerthickness, however, the atoms of each layer must undergolonger random walks to achieveL10 phase, meaning the pat-tern of the original layer structuring is lost, resulting in~111!orientation. Although monatomic layering to achieve orien-tation may be ideal, as suggested by the work of Shimaet al.,8 our experiment shows that good orientation can beobtained with a multilayer Fe/Pt configuration deposited by amore conventional, nonepitaxial method that employs mag-netron sputtering.Figure 5 summarizes the systematic trends in perpen-dicular coercivity of@Fe (0.47 nm!/Pt (0.4 nm)#12 films as afunction of the annealing temperature and time. For filmsannealed at 400 °C, the coercivity is around 2–3 kOe. Therelatively small coercivity indicates that the film is not fullychemically ordered at this annealing temperature. As the an-nealing temperature increases, the transformed fraction of theL10 ordered phase increases and the highest coercivity valueobtained ~10 kOe! occurs when the film is annealed at550 °C. The coercivity remains almost unchanged as the an-nealing time increases. The average grain sizes estimatedfrom TEM grow from 8 to 12 nm when the annealing time ischanged from 5 s to 600 s.IV. CONCLUSIONL10 ordered FePt films with perpendicular anisotropywas successfully obtained by sputtering Fe/Pt multilayers di-rectly onto a glass substrate and subsequent rapid thermalannealing. This nonepitaxial~001! texture of FePt films canbe controlled by the initial multilayer structure and annealingprocesses. Nonepitaxially grownL10 FePt films are muchmore compatible with practical applications than thosegrown epitaxially.ACKNOWLEDGMENTSThis research was supported by the Department of En-ergy, Nebraska Research Initiative, Information Storage In-dustry Consortium, and Center for Materials Research andAnalysis.1B. M. Lairson, M. R. Visokay, R. Sinclair, and B. M. Clemens, Appl.Phys. Lett.62, 639 ~1993!.2M. Watanabe and M. Homma, Jpn. J. Appl. Phys., Part 235, L1264~1996!.3J.-U. Thiele, L. Folks, M. F. Toney, and D. K. Weller, J. Appl. Phys.84,5686 ~1998!.4A. Cebollada, D. Weller, J. Sticht, G. R. Harp, R. F. C. Farrow, R. F.Marks, R. Savoy, and J. C. Scott, Phys. Rev. B50, 3419~1994!.5H. Zeng, M. L. Yan, N. Powers, and D. J. Sellmyer, Appl. Phys. Lett.80,2350 ~2002!.6M. L. Yan, H. Zeng, N. Powers, and D. J. Sellmyer, J. Appl. Phys.91,8471 ~2002!.7M. L. Yan, N. Powers, and D. J. Sellmyer, Mater. Res. Soc. Symp. Proc.721, 291 ~2002!.8T. Shima, T. Moriguchi, S. Mitani, and K. Takanashi, Appl. Phys. Lett.80,288 ~2002!.FIG. 4. Ordering and texture development of FePt thin films with differentbilayer (DFe/DPt) thicknesses. The films were annealed at 550 °C for 5 s.DFe50.23 nm and DPt50.2 nm. ~a! 1DFe/1DPt , ~b! 2DFe/2DPt , ~c!4DFe/4DPt , ~d! 6DFe/6DPt , and~e! 8DFe/8DPt .FIG. 5. Coercivity behavior of@Fe (0.47 nm!/Pt (0.4 nm)#12 film as a func-tion of the annealing time and the annealing temperature. The annealingtemperature was fixed at 550 °C when the annealing time was changed andthe annealing time was 600 s when the annealing temperature was changed.8294 J. Appl. Phys., Vol. 93, No. 10, Parts 2 & 3, 15 May 2003 Yan, Powers, and SellmyerDownloaded 14 Nov 2006 to 129.93.16.206. Redistribution subject to AIP license or copyright, see http://jap.aip.org/jap/copyright.jsp

Highly oriented nonepitaxially grown \u3ci\u3eL\u3c/i\u3e1\u3csub\u3e0\u3c/sub\u3e FePt films

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
David Sellmyer Publications Research Papers in Physics and Astronomy 
5-15-2003 
Highly oriented nonepitaxially grown L10 FePt films 
M.L. Yan 
University of Nebraska - Lincoln 
Nathan D. Powers 
University of Nebraska-Lincoln, ndp5@byu.edu 
David J. Sellmyer 
University of Nebraska-Lincoln, dsellmyer@unl.edu 
Follow this and additional works at: https://digitalcommons.unl.edu/physicssellmyer 
 Part of the Physics Commons 
Yan, M.L.; Powers, Nathan D.; and Sellmyer, David J., "Highly oriented nonepitaxially grown L10 FePt films" 
(2003). David Sellmyer Publications. 31. 
https://digitalcommons.unl.edu/physicssellmyer/31 
This Article is brought to you for free and open access by the Research Papers in Physics and Astronomy at 
DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in David Sellmyer Publications 
by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
Highly oriented nonepitaxially grown L10 FePt films
M. L. Yan,a) N. Powers, and D. J. Sellmyer
Center for Materials Research and Analysis and Department of Physics and Astronomy,
University of Nebraska, Lincoln, Nebraska 68588
~Presented on 15 November 2002!
A method of preparing nonepitaxially grown, highly texturedL10 FePt thin films is described. A
nearly perfect~001! texture was obtained by direct deposition of FePt films on Corning 7059 glass
substrates and subsequent rapid thermal annealing. The ordering and orientation of theL10-phase
FePt grains were controlled by the initial as-deposited film structure, and also by the annealing
process. Magnetic measurements reveal large perpendicular anisotropy for these~001! textured
films. The substrates and processes used for nonepitaxial growth ofL10 rdered FePt films are much
more compatible with practical applications than those grown epitaxially. ©2003 American
Institute of Physics.@DOI: 10.1063/1.1556257#
I. INTRODUCTION
L10-phase FePt films have attracted much attention for
hard and semihard thin-film applications because of their
high magnetocrystalline anisotropy constant that promises
thermal stability of material with small grain size. Under
normal growth conditions,L10-phase FePt films often pos-
sess~111! preferred or random orientations. In order to con-
trol the crystal orientation, epitaxial growth of FePt film was
investigated by several deposition techniques including
sputtering1–3 and molecular-beam epitaxy~MBE!.4 The most
common methods by which to obtain thec axis normal to the
film plane @~001! texture# are to use seed or buffer layers
between a single-crystal substrate, such as MgO, and the
FePt thin films. In most cases, however, it is not convenient
or practical to use such methods. In the present study, we
report nonepitaxial, highly texturedL10 FePt thin films.
~001! texture has been successfully obtained by direct depo-
sition of films on glass substrates and subsequent rapid ther-
mal annealing~RTA!. The annealing temperature controls or-
dering of the FePt grains, and the annealing time controls the
orientation of the FePt grains. The orientation mechanism of
FePt films deposited on a glass substrate is totally different
from that of epitaxial films. We are able to fabricateL10
ordered FePt films in a very short annealing time and control
the orientation by adjusting the initial as-deposited film
structures and annealing processes.
II. EXPERIMENT
The samples were magnetron sputtered on Corning 7059
glass substrates with a multilayer structure of Fe/Pt. Targets
of Fe and Pt were commercial products with purity higher
than 99.9 at. %. The base pressure of the chamber was less
than 331027 Torr and a working pressure of 4 mTorr Ar
was used during sputtering. The substrates were mounted on
a water-cooled rotating table. The composition of the film
was well controlled by adjusting the thickness ratio of the Fe
and Pt layers. The typical total film thickness was 10 nm.
The as-deposited films were annealed by RTA from 350 to
650 °C for 2–600 s. The microstructural evolution of the
nonepitaxial growth and magnetic properties of these films
was investigated by x-ray diffraction~XRD!, transmission
electron microscopy~TEM!, alternating gradient magneto-
meter~AGFM! and a superconducting quantum interference
device~SQUID!.
III. RESULTS AND DISCUSSION
The ordering and orientation of the FePt films are depen-
dent on the annealing temperature and time, and~001! tex-
ture is obtained for the film that is less thick. Figure 1 shows
the ordering process of 10 nm FePt film as the annealing
temperature increases, characterized by the increase in inten-
sity of the superlattice peaks. FePt films were prepared by
Fe/Pt multilayer deposition with initial layer thickness of
0.47 nm Fe and 0.4 nm Pt. All films were annealed by RTA
a!Author to whom correspondence should be address; electronic mail:
myan@unlserve.unl.edu
FIG. 1. XRD patterns of@Fe (0.47 nm!/Pt (0.4 nm)#12 film annealed at dif-
ferent temperaturesTA for 600 s.TA5(a) as deposited and~b! 350,~c! 400,
~d! 450, ~e! 500, ~f! 550, and~g! 600 °C.
JOURNAL OF APPLIED PHYSICS VOLUME 93, NUMBER 10 15 MAY 2003
82920021-8979/2003/93(10)/8292/3/$20.00 © 2003 American Institute of Physics
Downloaded 14 Nov 2006 to 129.93.16.206. Redistribution subject to AIP license or copyright, see http://jap.aip.org/jap/copyright.jsp
for 300 s at different temperatures. As can be seen in Fig.
1~a!, the film is disordered face-centered-cubic~fcc! phase in
the as-deposited film. When annealing temperatureTA is
lower than 350 °C@Fig. 1~b!#, the film is still disordered fcc
phase. AsTA increases to 400–450 °C@Figs. 2~c! and 2~d!#,
~001! and ~002! peaks begin to appear, but they are broad
and their relative intensity is low, which means that the or-
dering process has just started. The overlap of the~200! and
~002! peaks means that the film is still a mixture of fcc and
face-centered-tetragonal~fct! phases. These results indicate
that the fcc to fct phase transition is incomplete when the
samples are annealed at lower temperature. ForTA above
500 °C, the~001! superlattice peak becomes stronger and the
~200! and ~002! peaks are separated@Fig. 1~e!#, indicating a
completely ordered phase. We also see that the intensities of
the ~001! and~002! peaks increase very quickly, whereas the
intensity of the~111! peak decreases as the annealing tem-
perature increases@Figs. 1~f! and 1~g!#. WhenTA is higher
than 550 °C, the~001! and~002! peaks become dominant and
the ~111! peak has almost disappeared@Fig. 1~g!#, which in-
dicates the high degree of~001! texture. This preferential
~001! orientation is quite significant since the@001# direction
is the easy axis of FePt, and usually FePt films with an easy
axis perpendicular to the film plane can be obtained only by
an epitaxial growth technique. Earlier we reported this pref-
erential~001! orientation in thinner CoPt,5 FePt:B2O3,
6 and
CoPt:B2O3 ~Ref. 7! nanocomposite films, and the degree of
orientation decreases as the film thickness increases. This
preferential~001! orientation may be affected by the proper-
ties of the interface between the substrate and the FePt mul-
tilayers. The first stage of growth of as-deposited films may
determine the initial nanostructure, and then the orientation
of postannealed films.6
Figure 2 shows XRD patterns of@Fe ~0.47 nm!/
Pt ~0.4 nm!#12 films annealed at 550 °C for different amounts
of time. The insets in Fig. 2 are the~001! peak rocking
curves. Superlattice peaks are clearly seen in Fig. 2~a!, indi-
cating theL10 ordered structure of FePt grains formed after
only 2 s of annealing. The broad~001! rocking curve and
relatively higher intensity of the~111! peak indicate de-
graded~001! texture and randomly oriented FePt grains. For
the sample annealed for 600 s, the~001! and~002! peaks are
dominant and the~111! peak is almost invisible@Fig. 2~b!#.
The rocking curve shows the narrow full width at half maxi-
mum ~FWHM! ~55.4°!, which indicates the high degree of
~001! texture in the film with a suitable amount of annealing.
Our results show that ordering of the FePt grains is very
sensitive to annealing temperatureTA , and that orientation
of the FePt grains is controlled by the annealing time. Figure
3 shows corresponding hysteresis loops of these two samples
measured by the SQUID with a field applied either in the
film plane or perpendicular to the film plane. Almost identi-
cal hysteresis loops were measured in both directions for the
sample annealed for 2 s@Fig. 3~a!#, which is consistent with
randomly oriented FePt grains. When annealed for 600 s
@Fig. 3~b!#, the film exhibits a square perpendicular loop with
a high remanence ratio, indicating the development of per-
pendicular anisotropy due to preferential~001! orientation.
The magnetic measurements are clearly compatible with the
XRD results.
Another experimental finding is that the orientations of
L10-phase FePt films are also dependent on the initial as-
deposited film structure. Figure 4 shows XRD patterns of
FePt films with different bilayer thicknesses. The films were
of the form of (NDFe/NDPt)n , in which DFe was a Fe layer
of 0.23 nm, andDPt was Pt layer of 0.2 nm.N was changed
from 1 to 8 andn ranged from 24 to 3 in order to keep the
nominal film thickness around 10 nm. All films were an-
nealed by RTA at 550 °C for 5 s. It is clearly seen that the
texture of the film is affected by the initial multilayer struc-
ture. Films are~001! textured when the Fe/Pt bilayer thick-
ess is small. When the bilayer thickness increases, the rela-
tive intensity of the~001! peak decreases and the intensity of
the~111! peak increases. WhenN increases to 8, the intensity
of ~111! increases and becomes dominant. Relatively high
~111! intensity and low~001! intensity indicate the develop-
ment of ~111! texture. This result shows that the texture of
the film changed from~001! to ~111! with the increase in
bilayer thickness. This preferential~001! texture appears to
be related to the configuration of the nearly monatomic lay-
FIG. 2. XRD patterns of@Fe (0.47 nm!/Pt (0.4 nm)#12 film annealed at
550 °C for different times:~a! 2 s and~b! 600 s. The insets show the~001!
rocking curves.
FIG. 3. Hysteresis loops of@Fe (0.47 nm!/Pt (0.4 nm)#12 film annealed at
550 °C for~a! 2 s and~b! 600 s. Closed circles represent out of plane loops
and open circles in plane loops.
8293J. Appl. Phys., Vol. 93, No. 10, Parts 2 & 3, 15 May 2003 Yan, Powers, and Sellmyer
Downloaded 14 Nov 2006 to 129.93.16.206. Redistribution subject to AIP license or copyright, see http://jap.aip.org/jap/copyright.jsp
ers. Alternate monatomic-layer deposited FePt films with
perpendicular anisotropy deposited at relatively low tem-
peratures have been reported.8 In our case, one can see from
Fig. 4 that samples comprised of thinner bilayers~in these
cases the layers are only a few atoms thick! acquire a strong
~001! texture upon annealing. In these cases the multilayers
already emulate an ordered~001! L10 phase. During subse-
quent annealing this requires that the atoms need only move
slightly to obtain a stable fct configuration. This preserves
the orientation prescribed by the multilayer geometry,
namely~001!. In the case of the samples with greater bilayer
thickness, however, the atoms of each layer must undergo
longer random walks to achieveL10 phase, meaning the pat-
tern of the original layer structuring is lost, resulting in~111!
orientation. Although monatomic layering to achieve orien-
tation may be ideal, as suggested by the work of Shima
et al.,8 our experiment shows that good orientation can be
obtained with a multilayer Fe/Pt configuration deposited by a
more conventional, nonepitaxial method that employs mag-
netron sputtering.
Figure 5 summarizes the systematic trends in perpen-
dicular coercivity of@Fe (0.47 nm!/Pt (0.4 nm)#12 films as a
function of the annealing temperature and time. For films
annealed at 400 °C, the coercivity is around 2–3 kOe. The
relatively small coercivity indicates that the film is not fully
chemically ordered at this annealing temperature. As the an-
nealing temperature increases, the transformed fraction of the
L10 ordered phase increases and the highest coercivity value
obtained ~10 kOe! occurs when the film is annealed at
550 °C. The coercivity remains almost unchanged as the an-
nealing time increases. The average grain sizes estimated
from TEM grow from 8 to 12 nm when the annealing time is
changed from 5 s to 600 s.
IV. CONCLUSION
L10 ordered FePt films with perpendicular anisotropy
was successfully obtained by sputtering Fe/Pt multilayers di-
rectly onto a glass substrate and subsequent rapid thermal
annealing. This nonepitaxial~001! texture of FePt films can
be controlled by the initial multilayer structure and annealing
processes. Nonepitaxially grownL10 FePt films are much
more compatible with practical applications than those
grown epitaxially.
ACKNOWLEDGMENTS
This research was supported by the Department of En-
ergy, Nebraska Research Initiative, Information Storage In-
dustry Consortium, and Center for Materials Research and
Analysis.
1B. M. Lairson, M. R. Visokay, R. Sinclair, and B. M. Clemens, Appl.
Phys. Lett.62, 639 ~1993!.
2M. Watanabe and M. Homma, Jpn. J. Appl. Phys., Part 235, L1264
~1996!.
3J.-U. Thiele, L. Folks, M. F. Toney, and D. K. Weller, J. Appl. Phys.84,
5686 ~1998!.
4A. Cebollada, D. Weller, J. Sticht, G. R. Harp, R. F. C. Farrow, R. F.
Marks, R. Savoy, and J. C. Scott, Phys. Rev. B50, 3419~1994!.
5H. Zeng, M. L. Yan, N. Powers, and D. J. Sellmyer, Appl. Phys. Lett.80,
2350 ~2002!.
6M. L. Yan, H. Zeng, N. Powers, and D. J. Sellmyer, J. Appl. Phys.91,
8471 ~2002!.
7M. L. Yan, N. Powers, and D. J. Sellmyer, Mater. Res. Soc. Symp. Proc.
721, 291 ~2002!.
8T. Shima, T. Moriguchi, S. Mitani, and K. Takanashi, Appl. Phys. Lett.80,
288 ~2002!.
FIG. 4. Ordering and texture development of FePt thin films with different
bilayer (DFe/DPt) thicknesses. The films were annealed at 550 °C for 5 s.
DFe50.23 nm and DPt50.2 nm. ~a! 1DFe/1DPt , ~b! 2DFe/2DPt , ~c!
4DFe/4DPt , ~d! 6DFe/6DPt , and~e! 8DFe/8DPt .
FIG. 5. Coercivity behavior of@Fe (0.47 nm!/Pt (0.4 nm)#12 film as a func-
tion of the annealing time and the annealing temperature. The annealing
temperature was fixed at 550 °C when the annealing time was changed and
the annealing time was 600 s when the annealing temperature was changed.
8294 J. Appl. Phys., Vol. 93, No. 10, Parts 2 & 3, 15 May 2003 Yan, Powers, and Sellmyer
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https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1030&amp;context=physicssellmyer

Highly oriented nonepitaxially grown \u3ci\u3eL\u3c/i\u3e1\u3csub\u3e0\u3c/sub\u3e FePt films

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