Embed Size (px)
Citation preview
Accepted Manuscript
Magnetic and structural properties of M-type barium hexaferrites films with transitionmetal substitutions
Lin Huang, Iwan Sugihartono, Djati Handoko, Dong-Seok Yang, Candra Kurniawan,Erfan Handoko, Dong-Hyun Kim
PII: S1567-1739(18)30331-6
DOI: https://doi.org/10.1016/j.cap.2018.12.008
Reference: CAP 4887
To appear in: Current Applied Physics
Received Date: 26 July 2018
Revised Date: 27 October 2018
Accepted Date: 11 December 2018
Please cite this article as: L. Huang, I. Sugihartono, D. Handoko, D.-S. Yang, C. Kurniawan,E. Handoko, D.-H. Kim, Magnetic and structural properties of M-type barium hexaferrites filmswith transition metal substitutions, Current Applied Physics (2019), doi: https://doi.org/10.1016/j.cap.2018.12.008.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service toour customers we are providing this early version of the manuscript. The manuscript will undergocopyediting, typesetting, and review of the resulting proof before it is published in its final form. Pleasenote that during the production process errors may be discovered which could affect the content, and alllegal disclaimers that apply to the journal pertain.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
1
Magnetic and Structural Properties of M-type Barium Hexaferrites
Films with Transition Metal Substitutions
Lin Huang1, Iwan Sugihartono
2, Djati Handoko
3, Dong-Seok Yang
4,
Candra Kurniawan5, Erfan Handoko
2a), and Dong-Hyun Kim
1b)
1Department of Physics, Chungbuk National University, Cheongju 28644, Korea
2Dept. of Physics, Jakarta State University (UNJ),Jakarta 13220, Indonesia
3Department of Physics, Universitas Indonesia, Depok 16424, Indonesia
4Department of Physics Education, Chungbuk National University, Cheongju
28644, Korea
5Research center for Physics, Indonesian Institute of Sciences (LIPI), Puspiptek
office area, South Tangerang, Indonesia
We have investigated the correlation between structural and magnetic properties of
M-type BaFe12O19 thin films ( ~ 1.4 m ) with Co-Ti (magnetic/non-magnetic) and
Co-Ni(magnetic/magnetic) substitution, as BaFe12-2xCoxTixO19 and
BaFe12-2xCoxNixO19 (0 ≤ x ≤ 1). With structural properties sensitively related to the
magnetic properties, where ferro-ferri phase transition is involved, it has been found
that magnetic properties can be substantially controlled by substitution concentration.
.
Key words : Hexaferrite film, magnetic element substitution, hexaferrite
structure, X-ray absorption spectra
____________________
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
2
1. INTRODUCTION
Since the discovery of magnetic M-type Barium hexaferrite (BaFe12O19 or BaM) in
the 1950s by Philips [1], it has attracted much attention due to possible applications in
wide ranges, such as high-density perpendicular recording [2], magnetic fluids [3,4],
and microwave/millimeter-wave devices [5-7], largely owing to its large
magnetocrystalline anisotropy [8], high saturation magnetization [9], excellent
chemical stability [10,11]. So far, numerous studies have been reported for magnetic
property modification of BaM by substitution of Ti4+
-Co2+
, Ti4+
-Zn2+
, Sn4+
-Co2+
,
Mo4+
-Co2+
, or Ir4+
-Co2+
ions [12-16] into BaM. Mostly, non-magnetic/magnetic
particles have been used in substitution while non-magnetic particle is used to control
the charge balance and magnetic particle is for magnetic property modification
[11,17]. It has been well known that the structural configuration at Fe sites [18] plays
a key role in determining magnetic properties for M-type ferrites with substitutions.
The crystallographic characteristics of five iron sites are found to be important, where
three out of five sites are octahedral sites (B), while the other two are tetrahedral (A)
and trigonal sites [19,20].
The magnetization of BaM results from the net moments in the magnetic ions on the
five sublattices [21]. At 0 K, BaM was known to have eight spins up and four spins
down, resulting in 20 Bohr magnetons per formula unit, which can be translated to a
saturation magnetization up to (4πMs) 529 KA/m [21]. It has been reported that
saturation magnetization (Ms) and coercivity (Hc) can be substantially varied, for
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
3
instance by substituting Co-Ti or Co-Ni as BaFe12-2xCoxTixO19 with lower x value
substitution [11,17,18,22], where Ms modification depends on the ferrites crystalline
degree upon the substitution [23-27]. In order to better understand and control the
physical and magnetic properties of the BaM, it is important to identify the exact
locations of the substituting ions in crystal. X-ray Absorption Fine Structure (XAFS)
is an effective spectroscopic tool for investigating the local bonding environments of
the specific atom, namely the nature of the electronic structure, the distance from the
neighboring atom, and the cationic site distribution.
So far, numerous studies have been devoted to understanding BaM properties of
powder or bulk. Very recently, BaM films, particularly with micron thickness, are
receiving increasing attention for device applications such as monolithic microwave
integrated circuit devices [28,29] and circulator/isolator in microwave communication
[30-33], while relatively little has been explored regarding the transition metal
substitution effect. Very recently, Co-Ti substitution in BaM thick films has been
explored [28], where drastic decrease in magnetic anisotropy and coercivity has been
reported, thereby hinting that substantial modification of magnetic properties might be
possible even in thin film cases. Therefore, further systematic study might be required
to explore the possibility of BaM film property modifications by substitution. In this
work, we report our investigation on structural and magnetic property modification
for BaM microfilms by two different substitution molds: non-magnetic/magnetic
(Co-Ti) particles and magnetic/magnetic (Co-Ni) particles with changing the
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
4
substitution composition from 0 to 1, where strong correlation between the degree of
crystallization monitored by XAFS and the magnetic properties are found for both
cases with exhibiting a dramatic decrease of Ms around a ferrimagnetic compensation
point. For magnetic property modification, Co played a major role in case of Co-Ti
substitution, whereas Ni played a dominant role in case of Co-Ni substitution.
2. EXPERIMENTS
Barium hexagonal ferrites thin films with substitution of Fe by Co2+
, Ni2+
, and
Ti4+
are prepared based on synthesized nanocrystalline BaFe12-2xCoxTixO19 and
BaFe12-2xCoxNixO19 with x = 0, 0.25, 0.5, 0.75, and 1. The film thickness was fixed to
be ~ 1.4 m . Moderate CA (citric acid) dissolved with 10 ml deionized water and
heated at 80 °C for 15 min. Then Fe(NO3)3, Ba(NO3)2, Co(NO3)2 and TiOSO4 were
poured into CA solution, followed by stirring by magnetic stirrer for 10 min. Then 10
ml deionized water was added and stirred again for 20 min. The solution was poured
into atomizing cup, closing the air flow, with waiting until the fog is formed in
atomizing cup. Then, opening the air flow, the solution was sprayed on the Quartz
(SiO2) substrate. Before spraying, the substrate was heated at 200 - 250 ℃ to
evaporate hydrogen content in the solution. The solution was sprayed on the substrate
evenly for 90 s, followed by sintering the substrate at 1000 ℃ for 1 hour.
The structural information was investigated by XAFS, XANES (X-ray Absorption
Near Edge Spectroscopy), and Scanning Electron Microscopy (SEM). XAFS is the
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
5
modulation of the x-ray absorption coefficient at energies near and above an X-ray
absorption edge of each element, providing structural information of neighboring
atoms. Similar technique based on the X-ray Absorption Spectroscopy is XANES,
which contain further information about local coordination and chemical state [34].
The XAFS measurement was carried out at the undulator beamline BL8C at Pohang
Accelerator Laboratory by fluorescence mode at room temperature. The hysteresis
measurement was carried out in room temperature condition by vibrating sample
magnetometer (VSM250, Dexing Magnet Ltd.) under up to 20 kOe of magnetic field
along the out-plane plane direction. By considering the thickness and area of the film
sample, the magnetization was determined in emu/g unit.
3. RESULTS AND DISCUSSION
The normalized XANES data at Fe-K edge of BaFe12-2xCoxTixO19 and
BaFe12-2xCoxNixO19 (x = 0, 0.25, 0.5, 0.75, and 1) thin films are shown in Fig. 1(a) and
Fig. 1(b), respectively. In Fig. 1(a), 2 dotted guidelines at 7129 and 7133 eV are
shown to denote the different oxidation states, corresponding to Fe3O4 and Fe2O3
absorption energy, respectively. Since Co2+
ion has a lower valence than Fe3+
ion, Ti4+
is required to maintain an electrical neutrality of the structure. Without substitution (x
= 0), a rather broad single peak is observed to be positioned in the middle of Fe3O4and
Fe2O3 absorption energies. This might be due to the nanogranular nature of the
structure, observed by SEM as in Fig. 2. Compared to the other film case [28], where
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
6
the thickness was about 80 m and the film was fabricated by screen printing
method, the film in the present study has a thickness of 1.4 m with nanogranular
sizes of few tens of nm, which might lead to a slightly shifted peak position with
broadening. According to the SEM images, as x value increases, it is observed that the
granular size first increases and then decreases. Therefore, it is expected that the
crystalline quality might be improved with proper amount of substitutions. Very
interestingly, after the substitution with Co-Ti, K edge energy position has been split
to the left (7129 eV) and right (7133 eV), as seen in the figure. The split peaks are
clearly observed for all cases of substitutions (x = 0.25 ~ 1.0). It is considered that
with substitution of Ti4+
, Fe absorption energy peak is shifted to the left to decrease
the Fe valence to Fe2+
. With the substitution of Co2+
, Fe absorption energy peak is
shifted to the right to increase the valence to Fe3+
. On the other hand, in Fig. 1(b), the
substitution of Co-Ni ions only causes the increase of valency of Fe2+
ions changing
to Fe3+
, indicated by rather one-directional (to the right) absorption energy shift to
7133 eV.
The Fourier transforms of the XAFS data in Fig. 1 are plotted in Fig. 3 as kk 3
at Fe-K edge as a function of radial distance with variation of x, where k is a wave
vector and k is a Fourier amplitude at k. 3 dotted lines are plotted to guide the
original peak position of BaM without any substitution. In case of Co-Ti substitution
(Fig. 3(a)), the first peak at 1.40 Å without substitution exhibits a shift to the right (~
1.43 Å) with substitution, while the second peak (2.50 Å) is shifted oppositely to the
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
7
left (2.43 Å) with substitution. The first peak corresponds to the nearest-neighboring
Fe-O coordinate peak. The peak shift to the right by the Co-Ti substitution is caused
by the first Fe-O single scattering forming Fe3+
-O bonding with longer distance
compared to Fe2+
-O. The shift of the second peak to the left might be caused by Ti4+
ions with ionic radius 0.605 Å that gradually replaces Fe3+
ions with radius of 0.645 Å
in B-sites, mainly from Fe-Co or Fe-Ti single scattering interactions. The third peak
appears around 3.10 Å is considered from the single and the multiple scattering by
more external cation or metal ions [11,36].
As seen in Fig. 3(b), in case of Co-Ni co-substitution, the first peak at 1.40 Å
without substitution shifts to the right as well, in a similar way described in Fig. 3(a).
The second peak around 2.50 Å almost stays still even with substitution, indicating
that Ni2+
and Co2+
ions did not change the distance between the Fe and Ni or Fe and
Co, as discussed in Fig.1(b). The weak third peak at 3.10 Å does not show any clear
sign of shift but becomes relatively weaker compared to the third peak in Fig. 3(a),
which might come from the more Ni adsorbed on the edge sites, reducing the
magnitude of the third peak [37].
We further investigated the structural properties by the XAFS at Co-K edge. Fig. 4
shows the Fourier transform of Co K-edge XAFS spectra for samples with Co-Ti
substitution. It has been reported that Co2+
ions occupies both the tetrahedral 4f1 and
octahedral 4f2 positions [38] with a preference on the tetrahedral 4f1 site [39]. The
main peak around 1.30 Å as denoted by the dotted guideline is ascribed to the first
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
8
nearest-neighbor Co-O coordination, which suggests that Co is predominantly
incorporated into A sites. Especially, the peak amplitude changes as the substitution
concentration x varies. As x increases, the peak amplitude reaches the maximum at x
= 0.5 and drops for x = 0.75 and 1, as shown in the inset figure. Therefore, it is
expected that the best crystallization degree of the films is found with Co2+
ions
substitution with x = 0.5, which is also consistent with the SEM observation of Fig. 2.
Fourier transform of XAFS spectra for Co-Ni substitution in BaM is shown in Fig.
5. In Fig. 5(a), Co K-edge Fourier transform spectra are plotted. The main peak
around 1.40 Å increases gradually as x increases as seen in the inset figure, implying
that the increase of the Co substitution at 4f1 and 4f2 sites with better crystallization
degree of the films. This could be inferred from the bulk cases, where Ni2+
ions
replace Fe3+
ions at 4f2 and 12k sites for lower substitution rates and prefers 12k
sites for larger amounts. In Fig. 5(b), Ni K-edge Fourier transform spectra are
plotted. The main peak amplitude varies with x, reaching the maximum at x = 0.75
with the best crystallization degree, as clearly seen in the inset figure, which is also
consistent with SEM observation result in Fig. 2.
We investigated the magnetic hysteresis of the BaFe12-2xCoxTixO19 (x = 0, 0.25, 0.5,
0.75, and 1) thin films by VSM at room temperature. Measured hysteresis loops are
showed in Fig. 6(a). Ms and Hc determined from the hysteresis loop is plotted in Fig.
6(b) as a function of x. It is clearly observed from Fig. 6(b) that Hc significantly
decreases even with lower substitution, which is compare to the previous report on
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
9
bulk or powder samples in Ref. [39,40], the Hc of films was more influence by its
anisotropy field.
We have experimentally confirmed that a similar behavior is also found in case of
thin films. Ms decreases with substitution, reaching the minimum at x = 0.5, then
increases again as x = 0.75 and 1. Again, a similar tendency was reported for Co-Ti
substitution into powder samples previously [11]. We have experimentally confirmed
again the Co-Ti substitution-dependent Ms behavior for the BaM thin films. The
magnetic moment of Fe3+
is B5 and the moment of Co2+
is B7.3 . Ti4+
is
non-magnetic so that the moment is B0 . Substitution of Co-Ti thus is expected to
reduce the net magnetic moment [11]. It is interesting to note that Ms increases again
for x = 0.75 and 1, which cannot be simply explained based on the reduced net
magnetic moments of Fe replaced by Co or Ti. There has been a report on a possible
ferro-ferri phase transition for BaM, known as Gorter model [17,22,41]. Antiparallel
alignment of magnetic moments of Fe and Co in a ferrimagnetic phase might
drastically reduce of Ms at x = 0.5, with a recovered Ms for x = 0.75 and 1, reaching
almost the same value for the case of no substitution. Therefore, the overall Ms
behavior is governed not simply by the net moment reduction, but by the exact
magnetic phase determined from the structure.
We have measured magnetic hysteresis of the BaFe12-2xCoxNixO19 (x = 0, 0.25, 0.5,
0.75, and 1) thin films as well. Measured hysteresis loops are showed in Fig. 7(a). Ms
and Hc determined from the hysteresis loop is plotted in Fig. 7(b) as a function of x. In
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
10
case of Co-Ni substitution, for BaFe12-2xCoxNixO19 (x = 0, 0.25, 0.5, 0.75, and 1) thin
films, Ni2+
ions with magnetic moment of B2 and Co2+
ions with B7.3 replace Fe
3+
ions (B5 ) at 12k and 4f1 sites, which might results in decrease of Ms. Here, the
minimum Ms at x = 0.75 is observed, while the degree of crystallization monitored by
Ni-K edge peak amplitude, as discussed in Fig. 5(b), was the best at x = 0.75.
Therefore, it is expected a similar mechanism as in the case of Co-Ti substitution like
a phase transition involved with ferrimagnetism exists as well in the case of Co-Ni
substitution. It is also interesting to note that the Ms behavior is rather sensitively
dependent on the Ni substitution compared to the Co substitution, implying that Ni
more effectively replaces 4f2 site. Ni might be better compared to Co in tuning the
magnetic properties of BaM films with substitution.
4. CONCLUSIONS
In conclusion, we report our experimental investigation on the correlation between
magnetic properties and the crystallization degree of BaM microthin films with Co-Ti
and Co-Ni substitutions. With the magnetic-nonmagnetic Co-Ti substitution, both Ms
and Hc significant decreased with x = 0.25. There existed the minimal value of Ms,
where the substitution amount x is accompanied by the increased degree of
crystallinity. The substantial variation of Ms cannot be simply explained based on the
effective magnetic moment sum, but implies the existence of ferro-ferri phase
transition. Similar behavior was observed for magnetic-magnetic Co-Ni substitution,
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
11
however, it has been found that the Ni, compared to Co, seems to replace Fe ions at
4f2 sites more effectively. Our experimental investigation indicates that most of
knowledge, explored previously in bulk or powder samples, can be similarly applied
to the microthin films of BaM, shedding a light in possible BaM film applications.
ACKNOWLEDGEMENTS
This work was supported by the National Research Foundation of Korea (NRF)
(Grant No. 2018R1A2B3009569) and the KBSI Grant D38614.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
12
Reference
[1] P. Hernandez-Gomez, J. M. Munoz, C. Torres, C.de Francisco and O.Alejos, J.
Phys. D: Appl. Phys. 36(2003) 1062-70.
[2] X. Y. Sui, M. Scherge, M. H. Kryder, J. E. Snyder, V. G. Harris and N. C.
Koon, J. Magn. Magn. Mater. 155(1996) 132-9.
[3] D. Primc, D. Makovec, D. Lisjak and M. Drofenik, Nanotech. 20 (2009)
315605.
[4] H. Zhao, Y. Du, L. Kang, P. Xu , L. Du, Z. Sun and X. Han, Crystengcomm
15(2013) 808.
[5] M. Mohebbi, K. Ebnabbasi, and C. Vittoria, IEEE Trans. Magn. 49(2013)
4207.
[6] P. Shi, H. How, X. Zuo, S. D. Yoon, S.A. Oliver and C. Vittoria, IEEE Trans.
Magn. 37(2001) 2389.
[7] V. G. Harris, Z. Chen, Y. Chen, S. Yoon, T. Sakai, A. Geiler, A. Yang, Y. He, K.
S. Ziemer, N. X. Sun and C. Vittoria, J. Appl. Phys. 99(2006) 08M911.
[8] S. Capraro, M. Le Berre, J. P. Chatelon, H. Joisten, E. Mery, B. Bayard, J. J.
Rousseau and D. Barbier, Sensor Actuators A, 113 (2004)382.
[9] R. C. Pullar, Prog. Mater. Sci. 57(2012) 1191.
[10] Y. C.Du, H. B. Gao, X. R. Liu, J. Y. Wang, P. Xu and X. J. Han, J. Mater. Sci.
45(2010) 2442.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
13
[11] J. Li, H. Zhang, Y. Liu, Y. Liao, G. Ma and H. Yang, Mater. Res. Expr.
2(2015) 046105.
[12] Q. A. Pankhurst, D. H. Jones and A. H. Morrish, Proceedings ICF-5, India
(1986)323.
[13] P. Wartewig, M. K. Krause and P. Esquinari, J. Magn. Magn. Mater.
192(1999) 83.
[14] X. Batlle, M. Pernet and X. Obrador, Proceedings ICF-5, India (1989) 423.
[15] D. G. Agresti, T. D. Shelfer and Y. K. Hong, IEEE Trans. Magn. 25(1989)
4069.
[16] B. Sugg and H. Vincent, J. Magn. Magn. Mater. 139(1995) 364.
[17] S. Bierlich, T. Reimann, H. Bartsch, J. Topfer, J. Magn. Magn. Mater.
384(2015) 1.
[18] T. Toyoda, K. Kitagawa, J. Ceram. Soc. Japan, 112(2004) S1455.
[19] J. Smit and H. P. J. Wijn, Ferrite Philips Technical Library, Eindhoven,1959.
[20] A. Yang, Y. Chen, Z. Chen, C. Vittoria and V. G. Harris, J. Appl. Phys.
103(2008) 07E511.
[21] T. Toyoda, K. Kitagawa, J. Ceram. Soc. Japan, 112(2004) S1455.
[22] X. Batlle, X. Obradors, J. Rodrigues-Carvajal, M. Pernet, M. V. Cabanas and
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
14
M. Vallet, J. Appl. Phys.70 (1991)1614.
[23] H. Sozeri, J Alloys Compd. 486(2009) 809.
[24] U. Topal and H. I. Bakan, J. Eur. Ceram. Soc, 30(2010) 3167.
[25] P. E. Garcia-Casillas, A. M. Beesley, D. Bueno, J. A. Matutes-Aquino and C.
A. Matinez. J. Alloys Compd. 369 (2004) 185.
[26] J. Dho, E. K. Lee, J. Y. Park and N. H. Hur, J. Magn. Magn. Mater. 285(2005)
164.
[27] M. M. Rashad, M. Radwan and M. M. Hessien, J. Alloys Compd. 453 (2008)
304.
[28] S. Verma, O. P. Pandey, A. Paesano Jr., P. Sharma, J. Alloys Compd. 678
(2016) 284.
[29] S. D. Yoon and C. Vittoria, J. Appl. Phys. 93(2003) 8597.
[30] J. D. Adam, S. V. Krishnaswamy, S. H. Talisa, and K. C. Yoo, J. Magn. Magn.
Mater. 83(1990) 419 .
[31] H. L. Glass, Proc. IEEE, 76(1988) 151.
[32] C. A. Carosella, D. B. Chrisey, P. Lubitz, J. S. Horwitz, P. Dorsey, R. Seed,
and C. Vittoria, J. Appl. Phys. 71(1992) 5107.
[33] P. C. Dorsey, D. B. Chrisey, J. S. Horwitz, P. Lubitz, and R. C. Y. Auyeung,
IEEE Trans. Magn. 30 (1994) 4512 .
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
15
[34] J. J. Rehr, R. C. Albers, Rev. Mod. Phys., 72 (2000) 3.
[35] N.-E. Sung, I.-J. Lee, S. Jeong and S.-W. Kang, J. Synchr. Rad. 21
(2014) 1282-1287.
[36] L. Wang, J. Zhang, Q. Zhang, N. Xu and J. Song, J. Magn. Magn. Mater. 377
(2015) 362.
[37] H. Yin, H. Li, Y. Wang, G. V. Matthew, G. Qiu, X. Feng, L. Zheng and F. Liu,
Chem. Geology, 381 (2014) 10–20.
[38] Z. Simsa, S. Logo, R. Gerber, E. Pollert, J. Magn. Magn. Mater. 140-144
(1995) 2103.
[39] J. Kreisel, H. Vincent, F. Tasset, M. Pate and J. P. Ganne, J. Magn. Magn.
Mater. 224(2001) 17.
[40] A. Grusková, J. Sláma, R. Dosoudil, D. Kevická, V. Jančárik and I. Tóthc, J.
Magn. Magn. Mater. 423 (2002) 242-245.
[41] J. C. Gómez Sal, F. Rodίguez González, J. M. Barandiarán, F. Plazaola, and
T. Rojo (Eds.), Spanish Scientific Research Using Neutron Scattering Techniques,
E-Publishing Inc., Spanish, 1986-1991, pp. 50-51.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
16
FIGURE CAPTIONS
Fig. 1. XANES at Fe-K edge for (a) BaFe12-2xCoxTixO19 and (b) BaFe12-2xCoxNixO19
films with x = 0, 0.25, 0.5, 0.75, and 1.
Fig. 2. SEM micrographs for BaM with Co-Ti or Co-Ni substitutions. Upper right
image is for thickness estimation
Fig. 3. Fourier transform of Fe K-edge XANES spectra for the case of (a) Co-Ti
substitution and (b) Co-Ni substitution.
Fig. 4 Fourier transform of Co K-edge XANES spectra in case of Co-Ti substitution.
Inset figure shows peak amplitudes of Fourier transform spectra with respect to x.
Fig. 5 Fourier transform of (a) Co-K edge and (b) Ni-K edge XANES spectra with
variation of x from 0.25 to 1. Inset figures show peak amplitudes of Fourier transform
spectra with respect to x.
Fig. 6. (a) Hysteresis loops of BaFe12-2xCoxTixO19 thin films measured at room
temperature. (b) Ms and Hc with respect to the Co-Ti substitution amount x.
Fig. 7. (a) Hysteresis loops of BaFe12-2xCoxNixO19 thin films measured at room
temperature. (b) Ms and Hc with respect to the Co-Ni substitution amount x.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
17
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
18
Figure 1
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
19
Figure 2
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
20
Figure 3
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
21
Figure 4
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
22
Figure 5
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
23
Figure 6
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
24
Figure 7
