Magnetic properties of Ni substituted Y-type barium ferriteMi Hee Won and Chul Sung Kim

Citation: Journal of Applied Physics 115, 17A509 (2014); doi: 10.1063/1.4860939 View online: http://dx.doi.org/10.1063/1.4860939 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 The crystal structure and magnetic properties of Ba2xSrxCo2Fe12O22 J. Appl. Phys. 115, 17A523 (2014); 10.1063/1.4866892 Magnetic properties of Zn doped Co2Y hexaferrite by using high-field Mössbauer spectroscopy J. Appl. Phys. 115, 17A516 (2014); 10.1063/1.4865879 Effect of Ni substitution on Y-type barium ferrite J. Appl. Phys. 113, 17D906 (2013); 10.1063/1.4794879 Sintering effect on structural and magnetic properties of Ni 0.6 Zn 0.4 Fe 2 O 4 ferrite AIP Conf. Proc. 1512, 1160 (2013); 10.1063/1.4791460 Effect of aluminum substitution on microwave absorption properties of barium hexaferrite J. Appl. Phys. 98, 103905 (2005); 10.1063/1.2135412

[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

195.132.111.47 On: Fri, 11 Apr 2014 15:35:34

Magnetic properties of Ni substituted Y-type barium ferrite

Mi Hee Won and Chul Sung Kima)

Department of Physics, Kookmin University, Seoul 136-702, South Korea

(Presented 6 November 2013; received 23 September 2013; accepted 14 October 2013; published

online 28 January 2014)

Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas

and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type

hexaferrites have higher magnetic ordering temperature than other Y-type. We have investigated

macroscopic and microscopic properties of Y-type barium hexaferrite. Ba2Co2�xNixFe12O22 (x¼ 0, 0.5,

1.0, 1.5, and 2.0) samples are prepared by solid-state reaction method and studied by X-ray diffraction

(XRD), vibrating sample magnetometer, and M€ossbauer spectroscopy, as well as a network analyzer for

high frequency characteristics. The XRD pattern is analyzed by Rietveld refinement method and

confirms the hexagonal structure with R-3m. The hysteresis curve shows ferrimagnetic behavior.

Saturation magnetization (Ms) decreases with Ni contents. Ni2þ, which preferentially occupies the

octahedral site with up-spin sub-lattice, has smaller spin value S of 1 than Co2þ having S¼ 3/2. The

zero-field-cooled (ZFC) measurement of Ba2Co1.5Ni0.5Fe12O22 shows that Curie and spin transition

temperatures are found to be 718 K and 209 K, respectively. The Curie temperature TC is increased with

Ni contents, while TS is decreased with Ni. The M€ossbauer spectra were measured at various

temperatures and fitted by using a least-squares method with six sextet of six Lorentzian lines for Fe

sites, corresponding to the 3bVI, 6cIV*, 6cVI, 18hVI, 6cIV, and 3aIV sites at below TC. From M€ossbauer

measurements, we confirmed the spin state of Fe ion to be Fe3þ and obtained the isomer shift (d),

magnetic hyperfine field (Hhf), and the occupancy ratio of Fe ions at six sub-lattices. The complex

permeability and permittivity are measured between 100 MHz and 4 GHz, suggesting that Y-type

barium hexaferrite is promising for antenna applications in UHF band. VC 2014 AIP Publishing LLC.

[http://dx.doi.org/10.1063/1.4860939]

I. INTRODUCTION

Since Y-type hexaferrites were discovered in 1950s, they

have attracted much attention and been extensively used in appli-

cations such as high-frequency antennas, RF devices, and micro-

wave devices.1,2 Here, magnetic properties such as magnetic

ordering temperature, saturation magnetization, and permeability

are important factors to enhance the device performance.

Especially, Y-type hexaferrites have higher permeability than

spinel ferrites have in the GHz frequency range. Also, due to its

high magnetic planar anisotropy, cut-off frequency of Y-type

hexaferrites is relatively higher than others. Therefore, Y-type

hexaferrites largely meet the need of soft magnetic materials.3

We have studied the magnetic properties of Ni substi-

tuted Y-type barium ferrite to investigate the correlation

between its characteristics, such as saturation magnetization,

magnetic ordering temperature, hyperfine field, and perme-

ability, using XRD, VSM, M€ossbauer spectroscopy, and net-

work analyzer (Agilent Technologies E5071C).

II. EXPERIMENT

The samples of Ba2Co2�xNixFe12O22 (x¼ 0, 0.5, 1.0, 1.5,

and 2.0) materials were synthesized using the solid-state reac-

tion method with high purity BaCO3 (99.98%), CoO (99.99%),

NiO (99.99%), and Fe2O3 (99.99%) powders. These were

mixed with appropriate stoichiometric ratio and ground for 1 h

in an agate mortar. The mixtures were calcined at 1000 �C for

10 h and palletized, followed by heating up to 1100 �C for 10 h,

at a rate of 2 �C/min. The crystal structure were analyzed by

XRD with Cu-Ka radiation (k¼ 1.5406 A). Magnetic properties

were measured using VSM at various temperatures. Also, the57Fe M€ossbauer spectra were recorded using a 50 mCi of 57Co

source in the Rh matrix with the spectrometer moving at con-

stant acceleration. Network analyzer was used to measure per-

meability and permittivity from 100 MHz to 4 GHz.

III. RESULTS AND DISCUSSION

Figure 1 shows the refined XRD patterns of

Ba2Co2�xNixFe12O22 (x¼ 0, 0.5, 1.0, 1.5, and 2.0). It is deter-

mined by Rietveld-refinement with the FULLPROF code. All

samples are rhombohedral with space group R-3m. The lattice

constants (a0, c0) and cell volume(Vu) of samples decrease with

Ni contents due to substitution of Ni2þ with ionic radius of

0.69 A for Co2þ ion having radius of 0.745 A. The samples of

x¼ 0, 0.5, and 1.0 are single-phased, but x¼ 1.5 and 2.0 sam-

ples have BaFe2O4 impurity phase, present at 2h¼ 27.831�,because of the incomplete reaction during the preparation pro-

cess. Although BaFe2O4 phase is present, XRD patterns of

x¼ 1.5 and 2.0 show mainly Y-type hexaferrites peaks.

Figure 2 shows the magnetic hysteresis loops of

Ba2Co2�xNixFe12O22(x¼ 0, 0.5, 1.0, 1.5, and 2.0) measured

at 295 K under 10 kOe. The hysteresis loops of all samples

show ferrimagnetic behavior. The values of MS for x¼ 0,

0.5, 1.0, 1.5, and 2.0 were MS¼ 29.1, 27.3, 24.6, 21.8, and

a)Author to whom correspondence should be addressed. Electronic mail:

cskim@kookmin.ac.kr.

0021-8979/2014/115(17)/17A509/3/$30.00 VC 2014 AIP Publishing LLC115, 17A509-1

JOURNAL OF APPLIED PHYSICS 115, 17A509 (2014)

[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

195.132.111.47 On: Fri, 11 Apr 2014 15:35:34

19.8 emu/g, respectively. The decrease in MS is due to the

fact that the spin value of Ni2þ (S¼ 1), preferentially occu-

pying the octahedral site with up spin sub-lattice, has smaller

than that of Co2þ (S¼ 3/2).

Figure 3 shows the temperature dependence of zero-

field-cooled (ZFC) magnetization curves at 100 Oe between

50 and 740 K. x¼ 0, x¼ 0.5, and x¼ 1.0 samples of ZFC

magnetization curves are presented in Ref. 8. All the samples

have drastic increase of magnetization at 715 K, 718 K,

720 K, 725 K, and 730 K for x¼ 0, 0.5, 1.0, 1.5, and 2.0, sug-

gesting the magnetic structure transition from ferrimagnet to

paramagnet. These transition points Tc increases with Ni

content, indicating the strong super-exchange interactions

with increasing x.4 The peaks in the magnetization curves at

215 K, 209 K, 204 K, and 165 K for x¼ 0, 0.5, 1.0, and 1.5

denote the transition points from the ferromagnetic ordered

state to an helimagnetic ordered state.5 In x¼ 2 samples, the

ferrimagnetic phase remains at lowest temperature.6 In

x� 1.5 samples, the transition temperature from the ferri-

magnetic to the helimagnetic ordered state decreases with x.

Figure 4 shows the frequency dependence of permeabil-

ity (l0) and magnetic loss (tandl¼ l00/l0) spectra of

Ba2Co1.5Ni0.5Fe12O22 in the range of 100 MHz and 4 GHz.

The permeability remains almost constant up to 4 GHz

between 1.5<l< 2. Also, the magnetic loss is small, having

tandl� 0.1. The permeability and magnetic loss spectra for

x¼ 1.0, 1.5, and 2.0 between 100 MHz and 4 GHz show sim-

ilar permeability ranging from 1.5 to 2. When x¼ 0.5, the

sample shows the highest permeability and lowest magnetic

loss as shown in Figure 4. Because permeability is generally

proportional to MS, x¼ 0.5 sample has highest permeability

as expected.7 These results indicate the potential antenna

application in GHz range. To further elucidate this, we have

carried out the detailed investigation of the microscopic

properties of the samples by M€ossbauer spectroscopy.

FIG. 1. Refined XRD patterns of Ba2Co2�xNixFe12O22 (x¼ 0.0, 0.5, 1.0, 1.5,

and 2.0) at 295 K.

FIG. 2. The applied-field dependence of the magnetization hysteresis curves

of Ba2Co2�xNixFe12O22 (x¼ 0.0, 0.5, 1.0, 1.5, and 2.0) up to 10 kOe at 295 K.

FIG. 3. The temperature dependence of the ZFC magnetization curves under

100 Oe between 50 and 740 K.

FIG. 4. Frequency dependence of permeability (solid line) and magnetic

loss (dashed line) for Ba2Co1.5Ni0.5Fe12O22 at 295 K.

17A509-2 M. H. Won and C. S. Kim J. Appl. Phys. 115, 17A509 (2014)

[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

195.132.111.47 On: Fri, 11 Apr 2014 15:35:34

To determine the distribution of iron ions and hyperfine

interaction in Ba2Co2�xNixFe12O22 (x¼ 0,0.5,1.0, 1.5, and

2.0), we obtained the M€ossbauer spectra at various tempera-

tures from 4.2 to 720 K. Figure 5 shows the analysis of

M€ossbauer spectra of Ba2Co1.5Ni0.5Fe12O22 samples from 4.2

to 720 K. These results can provide the values of Hhf, isomer

shift (d), and relative area of Fe ions with Ni substitution.8 At

temperature below TC, the spectra were fitted by using a

least-squares method with six sextet of six Lorentzian lines

for Fe sites corresponding to the 3bVI, 6cIV*, 6cVI, 18hVI, 6cIV,

and 3aIV sites.9 Among these sites, the 18hVI site has the

strongest hyperfine field (Hhf) with many adjacent magnetic

ions, followed by 3bVI, 6cIV, 6cIV*, 6cVI, and 3aVI. This differ-

ence in Hhf is due to the different internal organization of the

S- and T-block.10 The value of isomer shift between 0.17 and

0.39 mm/s indicates that the high spin Fe3þ state exists at all

temperature ranges. Because super-exchange interaction is

strong with decreasing temperature, the magnetic hyperfine

field increases with decreasing temperature.

IV. CONCLUSION

In summary, we have investigated the magnetic properties

of Y-type hexaferrite Ba2Co2�xNixFe12O22 (x¼ 0.0, 0.5, 1.0 1.5,

and 2.0). The samples are rhombohedral with space group R-3m.

The lattice constants and the unit cell volume decrease with

increasing Ni concentration. Also, Ms decreases with Ni, due to

the smaller spin value of Ni than that of Co. The temperature de-

pendence of the magnetization with x of 0.0, 0.5, 1.0, 1.5, and

2.0 shows that TC was increasing with Ni contents, while TS was

decreasing with increasing Ni substitution, finally disappearing

for x¼ 2.0. Frequency dependence of permeability (l0) and mag-

netic loss (tandl) spectra in the range of 100 MHz and 4 GHz

show that x¼ 0.5 has highest permeability and lowest magnetic

loss, suggesting the potential antenna application in GHz range.

Especially, for Ba2Co1.5Ni0.5Fe12O22, the distribution of iron ions

and hyperfine interactions has been studied with M€ossbauer

spectroscopy to understand its microscopic properties.

ACKNOWLEDGMENTS

This work was supported by Mid-career Researcher

Program through the National Research Foundation of Korea

(NRF) grant funded by the Ministry of Education, Science and

Technology (MEST) (No. 2013-000671).

1R. C. Pullar, Prog. Mater. Sci. 57, 1191–1334 (2012).2J. Jalli, Y.-K. Hong, S. Bae, J.-J. Lee, G. S. Abo, J.-H. Park, B.-C. Choi, T.

Mewes, S.-G. Kim, S.-H. Gee, I.-T. Nam, and T. Tanaka, J. Appl. Phys.

109, 07A509 (2011).3J. Smit and H. P. J. Wijn, Ferrites (Phillips Technical Library, Eindhoven,

1959).4B. D. Cullity, Introduction to Magnetic Materials (Addison Wesley,

Reading, MA, 1972).5G. Albanese, A. Deriu, F. Licci, and S. Rinaldi, IEEE Trans. Magn. 14,

710 (1978).6Y. Hiraoka, H. Nakamura, M. Soda, Y. Wakabayashi, and T. Kimura,

J. Appl. Phys. 110, 033920 (2011).7Y. Bai, J. Zhou, Z. Gui, Z. Yue, and L. Li, J. Magn. Magn. Mater. 264, 44

(2003).8M. H. Won and C. S. Kim, J. Appl. Phys. 113, 17D906 (2013).9J. T. Lim, C. M. Kim, B. W. Lee, and C. S. Kim, J. Appl. Phys. 111,

07A518 (2012).10I. Orlov, L. Palatinus, A. Arakcheeva, and G. Chapuis, Acta Crystallogr. B

63, 703 (2007).

FIG. 5. M€ossbauer spectra of Ba2Co1.5Ni0.5Fe12O22 at various temperatures.

17A509-3 M. H. Won and C. S. Kim J. Appl. Phys. 115, 17A509 (2014)

[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

195.132.111.47 On: Fri, 11 Apr 2014 15:35:34