Accepted Manuscript Synthesis, Structural, Magnetic and Dielectric Properties of Zirconium Copper doped M-type Calcium Strontium Hexaferrites Muhammad Naeem Ashiq, Raheela Beenish Qureshi, Muhammad Aslam Malana, Muhammad Fahad Ehsan PII: DOI: Reference:
S0925-8388(14)01870-2 http://dx.doi.org/10.1016/j.jallcom.2014.08.015 JALCOM 31868
To appear in:
Journal of Alloys and Compounds
Received Date: Revised Date: Accepted Date:
1 July 2014 31 July 2014 1 August 2014
Please cite this article as: M.N. Ashiq, R.B. Qureshi, M.A. Malana, M.F. Ehsan, Synthesis, Structural, Magnetic and Dielectric Properties of Zirconium Copper doped M-type Calcium Strontium Hexaferrites, Journal of Alloys and Compounds (2014), doi: http://dx.doi.org/10.1016/j.jallcom.2014.08.015
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Synthesis, Structural, Magnetic and Dielectric Properties of Zirconium Copper doped M-type Calcium Strontium Hexaferrites Muhammad Naeem Ashiqa, Raheela Beenish Qureshia, Muhammad Aslam Malana*a and Muhammad Fahad Ehsanb a
Institute of Chemical Sciences, BahauddinZakariya University, Multan-60800, Pakistan.
b
National Center for Nanoscience & Technology (NCNST), 11 Beiyitiao, Zhongguawn, Beijing, China * = Corresponding Author E-mail:
[email protected] Tel:+92-61-9210092 Fax: +92-61-9210085 Abstract Zirconium copper substituted calcium strontium hexagonal ferrites with composition Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0, 0.2, 0.4, 0.6, 0.8) have been synthesized by the chemical co precipitation procedure. These compounds were characterized by X-ray diffraction, Thermogravimetry and scanning electron microscopy. Dielectric and magnetic properties of these hexaferrites were also explored. XRD analysis confirmed the single hexagonal phase of all the compounds and the average crystallite size was between 37 and 47nm. The dielectric parameters show relaxation behaviour at higher frequencies. The values of dielectric parameters increase with dopants. In the range of magnetic field studied, the saturation magnetization decreases as the dopant contents increase which may be due to the nonmagnetic character of the substituents. The coericivity of the Zr-Cu doped derivatives of strontium calcium hexaferrites is increased up to x=0.2 and then decreased. The values of coericivity are above 600Oe which make them suitable materials for use in industries in longitudinal magnetic recording media. Keywords:
Nanostructured
materials,
Chemical
Synthesis,
Magnetization, X-ray Diffraction, Scanning electron microscopy.
Dielectric
response,
1
Introduction
Hexagonal ferrites have gained lots of attention due to their remarkablephysical and chemical properties since last few decades. Exhaustive research work on these ferrites has been initiated due to their captivating applications in microwave devices, computer memory chip, transformer, radio frequency coils, micro strip antennas and high density recording media [1, 2]. Ferrites with hexagonal structure can be classified into six different classes: M-type (AFe12O19), W-type (AB2Fe16O27), X-type (A2B2Fe20O46), Y-type (A2B2Fe12O22), Z-type (A3B2Fe24O41) and U-type (A4B2Fe36O60) where A represents Ba, Sr, Pb, Ca and B is bivalent cations of transition metal like Ni, Co, Zn [3] etc. The M-type nanohexagonal ferrite structure is based on hexagonal crystal lattice with 64 ions per unit cell on 11 different symmetry sites. In this structure smaller Fe3+cations are arranged over five distinct interstitial sites namely three octahedral sites (12k, 2a, 4f2), one tetrahedral (4f1) and one trigonal bipyramidal site (2b) [4] in which 5 oxygen atoms surround the Fe3+cation. Excellent magnetic behaviour of these ferrites can be described by the ordering of magnetic moments of the Fe3+cations and the super exchange interaction, in which three parallel (12k, 2a, 2b) and two antiparallel sites (4f1, 4f2) are coupled via O2-ions [5].These hexaferrites (M-type) have been widely studied because of their magnificent chemical stability, greater microwave magnetic loss, high Curie temperature and relatively large magnetization [6,7]. At higher frequency region, these nanomaterials are considered more useful as compared to other magnetic materials attributable to their good electrical properties such as low eddy current losses and high resistivity [8]. The electrical and magnetic properties of hexaferrites are influenced by the method of synthesis, average particle size, chemical composition and dopants [9-11]
.
In general, the typical method to obtain the metal oxide materials is solid state reaction at high temperature i.e. 1200oC [12]. However, it is very difficult to synthesize pure, strain free, smaller particle size and homogenous nanohexagonal ferrites by this typicalmethod. Hence, other methods such as aerosol pyrolysis [13], micro emulsion [14], dehydration and rotary evaporation, sol-gel combustion and chemical co-precipitation methods have also been employed [9]. In the present work, it was decided to use chemical co-precipitation method to prepare the nanomaterials having pure phase and small average crystallite size. The electrical and magnetic properties of the nanohexagonal ferrite materials can be modified by the addition of different cations at M (Ca, Sr, Ba, Pb) as well as Fe3+ sites. Various cations and combination of cations (bivalent-tetravalent) have been reported to
substitute in M-type hexaferrites by many researchers [9, 15-17]. Literature gives a lot of evidences of research on the SrFe12O19, BaFe12O19, Ba0.5Sr0.5Fe12O19 and their doped derivatives [9, 15-18]. However, Ca0.5Sr0.5Fe12O19 and its tetravalent-divalent cations substituted derivatives have received least attention. Therefore, the main focus of this work is to study the effect of substitution of Fe3+ by Zr4+ and Cu2+ on the electrical and magnetic properties of Ca0.5Sr0.5Fe12O19. Thermal and structural(SEM and XRD) analyses of the synthesized nanomaterials are also discussed in this manuscript. 2
Experimental
2.1
Chemicals
The chemicals used in this work are Fe(NO3)3.9H2O (97% Riedel Dehaen,), CaCl2.2H2O (99% Merck), Sr(NO3)3 (99%Fluka), ZrOCl2.8H2O(98% Merck), CuCl2.2H2O(99% Merck) and ammonia solution (33% Merck). 2.2
Synthesis of Sr0.5Ca 0.5Fe12-2xZrxCuxO19 (x=0.0-0.8)
Zirconium and copper doped M-type Sr-Ca hexaferrites with composition Sr0.5Ca0.5Fe122xZrxCu xO19
(x=0.0, 0.2, 0.4, 0.6, 0.8) have been synthesizedbychemical co-precipitation
method.The required amounts of the metal salts were dissolved in deionized water in each 250ml measuring flask to prepare the solutions. All these solutions were then homogenously mixed in a 2000ml beaker by using hot plate with magnetic stirrer. After half an hour, 4.0M ammonia solution (precipitating agent) was started to add drop wise in the reaction mixture and the pH of the reaction mixture was maintained between 10 and 11 to achieve the maximum precipitation. Then the solution was stirred at 343K for 3 hours. The resulted precipitates were washed by deionized water to take out their water soluble impurities i.e. nitrates and chlorides etc. and dried in an electric oven at 373K for 48 hours. The dried precursors were annealed at 1273K for 6 hours in a furnace (VULCANTM A-550) to obtain the single phase M-type hexagonal structure of the compounds. 2.3
Characterization
Thermogravimetric analysis (TGA) of the synthesized sample (Ca0.5Sr0.5Fe10.4Zr0.8Cu 0.8O19) was performedto observe structural changes during heating on Universal 4.2E TA Instruments. The nanomaterial was run from 303K to 1273K at heating rate of 10 oC/min. The crystalline structure of the synthesized hexaferrites was identified by PAnalytical X-ray
Diffractometer using CuKα as radiation source. The synthesized materials were characterized by Scanning electron microscope (JEOL-JSM-6700F) to visualize their microstructure i.e. shape, grain size and morphology. The magnetic properties of the synthesized materials at ambient temperature were studied by Lake Shore-74071 vibrating sample magnetometer (VSM). The dielectric properties of these samples were recorded as a function of frequency in the range 1MHz to 3GHz at room temperature by using a RF Impedence/Material Analyzer, Agilent E4991A. 3
Results and discussion
3.1
Thermal Analysis
TG curve of the unannealed sample Ca0.5Sr0.5Fe10.4Zr0.8Cu 0.8O19(Fig. 1) shows total weight loss of 19.01% in four steps. The first weight loss of 7.47% in the region 50-89oC can be attributed to the removal of free water. The second step of 3.51% weight loss in the region 90-207oC can be ascribed to the exclusion of hydrated water. A weight loss of 7.64% occurring in the range from 208-330 oC corresponds to the conversion of metal hydroxides to their oxides. The last weight loss of 0.39% in the region 331-751oC may be related to the beginning of formation of hexagonal phase in the metal oxides. 3.2
XRD analysis
X-Ray diffraction analysis was used to examine the crystalline structure and phase purity of the Ca0.5Sr0.5Fe12-2xZrxCu xO19 (x=0.0, 0.2, 0.4, 0.6, 0.8). The indexed powder XRD patterns of the prepared samples are shown in fig. 2. All the diffraction peaks were matched with ICSD pattern with reference code 01-080-1197. The XRD patterns confirm the formation of single phase magnetoplumbite structure (M-Type) in all the synthesized materials. The slight alteration in peak position may be attributed to the substitution of zirconium and copper. The separate peak of these substituted cations is not appeared which confirmed their successful substitution in the Ca0.5Sr0.5Fe12O19 [19]. The average crystallite sizes of all the samples were calculated by Scherrer’s formula (eq.1) [20]. D = kλ / β cos θ
(eq. 1)
Here λ is wavelength of X-rays used i.e. 1.541Å, β is full width at half maximum, θ is Bragg’s angle and K is Scherer’s constant i.e. 0.9. The average crystallite size was in the range of 37-
47nm that is much smaller than many of those already reported [21, 22].In order to obtain the suitable signal to noise ratio, the particle size less than 50nm is required in the high density recording media [23]. In the current studies, the synthesized compounds have particle size small enough (< 50nm) to get the suitable signal to noise ratio in high density recording media. 3.3
SEM Analysis
Scanning electron micrographs of the Sr0.5Ca0.5Fe12O19 and Sr0.5Ca0.5Fe12-10.8Zr0.6Cu 0.6O19 (Fig. 3a and 3b) were obtained to investigate their microstructure and grain size distribution. It can be seen that the undoped sample (Ca0.5Sr0.5Fe12O19)has a plate like structure having grain size between 0.263 and 1.05µm. The orientation of the grains is regular and the particles have narrow range of grain size. The Zr-Cu substituted derivative of M-type Sr-Ca hexaferrite (Fig. 3b) also shows the platelet like shape of the particles having grain size in the range of 0.263-4.208µm. It is clear from the figure that the particles indicate the strong inter grain connectivity by the doping of Zr4+ and Cu2+. 3.4
Magnetic Properties
The hysteresis loops of the synthesized Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0, 0.2, 0.4, 0.6, 0.8) are illustrated in fig. 4and the values of different magnetic parameters i.e. saturation magnetization (Ms), remanence (Mr) and coericivity (Hc) are given in table 1. In M-type hexaferrites, the Fe3+ ions inhabit three different symmetry sites i.e. octahedral, tetrahedral and trigonal bipyramidal. These Fe3+ ions are coupled via O2-anions by super exchange interaction ensuing in the formation of ferromagnetic structure [24-26]. In M-type hexaferrites, there are two formula units per unit cell and net magnetic moment of 20µB per formula unit [27]. The beginning of magnetic behaviour in ferrites is due to net magnetic moment of ions with up and down spin in various symmetry sites, as indicated by ferromagnetic theory. It is obvious from the table 1that the saturation magnetization and remanence fall as the concentration of dopants (Zr4+& Cu2+) increases. This decrease in Msfirstly,may be ascribed to the magnetic dilution due to the substitution of Fe3+ ions by nonmagnetic (Zr4+) and less magnetic (Cu2+) ions. Secondly, these dopants also lessen the super exchange interaction which may also cause the reduction of the saturation magnetization.
The squareness ratio (Mrs) of all the compounds, calculated as the ratio of remanence and saturation magnetization, is given in table 2. The compounds having squareness ratio ≥ 0.5 are in single magnetic domain while those having squareness ratio ≤ 0.5 are in multi magnetic domain[28].The squareness ratio of all the synthesized compounds is less than 0.5 thus making them multi magnetic domain. It is clear from table 1that the coericivity first increases when x=0.0-0.2 then drops in the remaining concentration range (x = 0.4 - 0.8) due to substitution of Zr4+& Cu 2+ ions.The initial increase may be due to the reduced magnetic exchange coupling [29] by the doping of nonmagnetic Zr4+ and less magnetic Cu 2+ ions.The abrupt fall in corecivity may be interpreted in terms of reduced magnetocrystalline anisotropy. It has been reported that the main contributors of magnetocrystalline anisotropy are 12k, 4f2 (octahedral) and 2b (trigonal bipyramidal) [30]. It is known that Cu 2+ions prefer to reside in 4f2 site while Zr4+ ions select to occupy the2b sites [31, 32]. These site preferences of dopant cations cause negative influence on magnetocrystalline anisotropy resulting in decreased coericivity of the compounds. The synthesized nanomaterials have coericivity value above 600Oe, making them valuable candidates in industries for longitudinal magnetic recording media [33]. Additionally, it was also pointed out [34] that if the value of coericivity is greater than Mr/2 the nanomaterials are hard magnets and these are considered valuable for high frequency applications. If the coericivity is less than Mr/2, then the nanomaterials are semi hard magnets and are useful in information storage technology [35]. In the current studies, all the synthesized zirconium and copper doped calcium strontium hexaferrites have Hc > Mr/2 thus these materials are hard ferrites and are beneficial in high frequency application. 3.5
Dielectric Measurements
3.5.1 Frequency Dependence The dielectric properties of the Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0, 0.4, 0.6, 0.8) were investigated in 1.0 MHz to 3.0GHz frequency range at ambient temperature. The frequency dependence of dielectric constant (ɛʹ), dielectric loss (ɛʹʹ) and dielectric tangent loss (tanδ) of the prepared ferrites is shown in fig. 5-7. It is apparent from the figs. that the ɛʹ, ɛʹʹ and tanδ are nearly constant up to a definite frequency i.e. 1.79-1.94 GHz, 1.91-1.98 GHz and 1.921.98 GHz, respectively, beyond which resonance type behaviour is observed. In general, the dielectric dispersion is greaterin low frequency regime (< 500Hz) and it comes to be independent of frequency when the intensity of the electric field increases. It may be
explained on the basis of induced electric moment in the material in the presence of external electric field. When frequency of the electric field rises, the polarization of the induced electric moment cannot synchronize the applied frequency. Hence, the dielectric material attains a constant value in high frequency regime [36]. In the current studies, the first constant trend of dielectric constant and dielectric loss may be related to the lack of coordination of induced electric moment with theelectric field as a result of which dielectric dispersion is nearly independent of applied frequency. After a certain frequency of the external field, the electronic exchange between Fe2+ and Fe3+becomes equal to the frequency of applied field therefore resonance type behaviour appears in the synthesized hexaferrites [37, 38]. First resonance peak appeared at lower frequency i.e. 1.791.98 GHzand second at higher frequency i.e. 2.52-2.58 GHz, in all synthesized samples. Former peak is ascribed to the interfacial polarization and later may be due to ionic relaxation. The high ionic relaxation in all the samples may be attributed to the variable valence state of ions [39]. It is also a probability that the synthesized nanomaterials may have higher magnitude of dielectric dispersion in low frequencies than the observed range because of space charge polarization at the grain boundaries as reported in literature for M-type hexaferrites [20]. 3.5.2 Composition dependence It can be seen from the fig. 8 that the dielectric constant (ɛʹ) and dielectric loss (ɛʹʹ) increaseby the substitution of Zr4+ and Cu2+ in place of two Fe3+ ions. The dielectric dispersion can be explained in terms of creation of electric dipoles of positive ions with their neighbouring O2ions but the principal source of polarization in ferrites is the hopping of electron between Fe3+ and Fe2+on octahedral symmetry sites. The jumping of electron (Fe2+ to Fe3+) produces local displacement of charge carriers, thus initiating the dielectric polarization and relaxation [4042]. The intensity of the hopping of electrons depends upon the number of Fe3+ - Fe2+ ion pair at the octahedral site in the unit cell of hexaferrites. It has been reported that the Zr4+ions substitute the Fe3+ ions at trigonal bipyramidal 2b site and Cu 2+ ions prefer to occupy octahedral (4f2) site.When the Zr4+ ions arrive into the 2b site then some Fe3+ ions of this site may transfer to the octahedral site thus enhancing the Fe3+ - Fe2+ ion pair at this site. Thisraises the interfacial polarization as well as theɛʹ and ɛʹʹ in the synthesized hexaferrites. It is observable from the fig. 8 that at the highest level of doping (x=0.8) the dielectric constant decreases. This drop may be due to the excess and dominancy of Cu2+at this doping level which lessensthe polarization owing to the reduction in Fe3+at octahedral (4f2) site thus,
dielectric constant shows decline. Hence, this material (x=0.8) is best among all the synthesized Zr-Cu doped derivatives of calcium strontium hexaferrites for high frequency applications [20]. Dielectric tan loss also exhibits the similar trend as that of the dielectric constant and dielectric loss (Fig. 10). 3.5.3 Room Temperature AC Conductivity Eq. 3 is used to calculate the room temperature Ac conductivity of the synthesized materials which is as follows:
σac = ωε o ε ′ tan δ
(eq.2)
ω=2πf The room temperature AC conductivity calculated for all compositions are plotted as afunction of frequency in fig. 9. It is seen from the figure that the ac conductivity slightly increases with frequency up to 1.95-1.98 GHz above which resonance type behaviour appears. This may be interpreted in a way that at lowrange of frequency, the jumping of electrons between Fe2+ and Fe3+ is less but as frequency goes to the higher values, the hopping of electrons is increased and conductivity is also increased [19]. It may be attributable that as compared to the activation of wide-ranging diffusive conduction, only a fraction of energy is required for the hopping (backward and forward) of the electrons [43]. As pointed out by Murthy and Sobhanadri, [44] there is a strong correlation concerning dielectric and conductivity mechanism in ferrites. They supposed that conduction mechanism in ferrites is similar to the polarization process which is due to electronic exchange between Fe3+ and Fe2+. It is also true in the present studies because the dielectric constant, dielectric loss, dielectric tan loss and conductivity (Fig.8 &10) show same trend by the inclusion of Zr4+ and Cu 2+ at the Fe3+sitein these synthesized compounds. 4
Conclusions
Coprecipitatively synthesized Zr-Cu doped strontium calcium hexaferrites have the average crystallite size in the range of 37-47nm which is small enough to obtain appropriate signal to noise ratio for high density recording media. Dielectric constant increases with increase in dopant concentration up to x=0.6 and then decrease (x=0.8). Due to small value of dielectric constant, the last sample (Ca0.5Sr0.5Fe10.4Zr0.8Cu0.8O19) may be suitable candidate in high frequency applications. The fall in saturation magnetization in the synthesized samples is
ascribed to the magnetic dilution and less super exchange interaction. Squareness ratio obtained for these compounds is less than 0.5 indicating their multi magnetic domain nature. The values of coericivity of all the synthesized samples are greater than Mr/2 reflecting their hard nature, thus, these samples are applicable in high frequency applications.
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Figure Captions Fig. 1: Thermogram of Sr0.5Ca0.5Fe10.4Zr0.8Cu0.8O19 Fig. 2: XRD patterns of Sr0.5Ca0.5Fe12-2xZrxCu xO19 (x=0.0, 0.2, 0.4, 0.6, 0.8) samples Fig. 3: SEM micrographs of A) Sr0.5Ca0.5Fe12O19 and B) Sr0.5Ca0.5Fe12-10.8Zr0.6Cu 0.6O19 Fig. 4: Hysteresis loops of the Sr0.5Ca0.5Fe12-2xZrxCu xO19 (x=0.0, 0.2, 0.4, 0.6, 0.8) samples Fig. 5 Frequency dependence of dielectric constant of the synthesized samples Ca0.5Sr0.5Fe122xZrxCu xO19 (x=0.0-0.8) at Room temperature Fig. 6a: Frequency dependence of dielectric loss (Ɛ") of the synthesized samples Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0 and 0.4) at Room temperature Fig. 6b: Frequency dependence of dielectric loss (Ɛ") of the synthesized samples Ca0.5Sr0.5Fe10.8Zr0.6Cu0.6O19 at Room temperature and inset represents the Frequency dependence of dielectric loss (Ɛ") of the Ca0.5Sr0.5Fe10.4Zr0.8Cu0.8O19 at Room temperature Fig. 7a: Frequency dependence of dielectric Tan loss of the synthesized samples Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0 and 0.4) at Room temperature Fig. 7b: Frequency dependence of dielectric tan loss of the Ca0.5Sr0.5Fe10.8Zr0.6Cu 0.6O19 and inset represents the Frequency dependence of dielectric tan loss of the Ca0.5Sr0.5Fe10.4Zr0.8Cu0.8O19 at Room temperature Fig. 8 Composition dependence of (Ɛ’ & Ɛ") of the synthesized compounds Ca0.5Sr0.5Fe122xZrxCu xO19 (x=0.0-0.8) at Room temperature Fig. 9a: Frequency dependence of conductivity of the samples Ca0.5Sr0.5Fe12Zr Cu O (x=0.0 and 0.4) at Room temperature 2x x x 19 Fig. 9b: Frequency dependence of conductivity of Ca0.5Sr0.5Fe10.8Zr0.6Cu 0.6O19 and inset represents the Frequency dependence of conductivity of the Ca0.5Sr0.5Fe10.4Zr0.8Cu 0.8O19 at Room temperature Fig. 10: Composition dependence of dielectric tan loss & conductivity of the synthesized compounds Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0-0.8) at Room temperature
100
3.27min 89.95°C 92.53%
Weight (%)
95
9.19min 207.25°C 89.02%
90
85
36.49min 751.10°C 80.99%
15.34min 330.47°C 81.38%
80 0
200
400
600
800
Temperature (°C)
Fig. 1: Thermogram of Sr0.5Ca0.5Fe10.4Zr0.8Cu0.8O19
1000 Universal V4.2E TA Instruments
x=0.0 114 202
107
1110
201
214
Intensity
006
107 201 205
006
107 201 006
205 205 107 201 205
006
10
20
30
300
300
0016
2110 2013
300
2110 2013
214 300
2110 2013
214 300
2110 2013
214
40
50
60
x=0.2 317
x=0.4
x=0.6
x=0.8 317
70
80
2 theta
Fig. 2: XRD patterns of Sr0.5Ca0.5Fe12-2xZrxCu xO19 (x=0.0, 0.2, 0.4, 0.6, 0.8) samples
Fig. 3: SEM micrographs of A) Sr0.5Ca0.5Fe12O19 and B) Sr0.5Ca0.5Fe12-10.8Zr0.6Cu 0.6O19
40
Magnetization (emu/g)
30 20
x=0.0 x=0.2 x=0.4 x=0.6 x=0.8
10 0 -10 -20 -30 -40 -100000-80000-60000-40000-20000
0
20000 40000 60000 80000100000
Magnetic field (Oe)
Fig. 4: Hysteresis loops of the Sr0.5Ca0.5Fe12-2xZrxCu xO19 (x=0.0, 0.2, 0.4, 0.6, 0.8) samples
x=0.0 x=0.4 x=0.6 x=0.8
40
35
Dielectric constant
30
25
20
15
10 0.00E+0005.00E+0081.00E+0091.50E+0092.00E+0092.50E+0093.00E+009
Frequency (Hz)
Fig. 5 Frequency dependence of dielectric constant of the synthesized samples Ca0.5Sr0.5Fe122xZrxCu xO19 (x=0.0-0.8) at Room temperature
Dielectric Loss
x=0.0 x=0.4 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6 0.00E+0005.00E+0081.00E+0091.50E+0092.00E+0092.50E+0093.00E+009
Frequency (Hz)
Fig. 6a: Frequency dependence of dielectric loss (Ɛ") of the synthesized samples Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0 and 0.4) at Room temperature
30 28 26 24
0.004
0.002
0.000
x=0.6
-0.002
22 -0.004
Dielectric Loss
20 -0.006
18 -0.008
16 -0.010
14
0.00E+000 5.00E+008 1.00E+009 1.50E+009 2.00E+009 2.50E+009 3.00E+009
12 10 8 6 4 2 0 -2 0.00E+0005.00E+0081.00E+0091.50E+0092.00E+0092.50E+0093.00E+009
Frequency (Hz)
Fig. 6b: Frequency dependence of dielectric loss (Ɛ") of the synthesized samples Ca0.5Sr0.5Fe10.8Zr0.6Cu0.6O19 at Room temperature and inset represents the Frequency dependence of dielectric loss (Ɛ") of the Ca0.5Sr0.5Fe10.4Zr0.8Cu0.8O19 at Room temperature
x=0.0 x=0.4 0.14 0.12 0.10 0.08
Dielectric loss
0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10 -0.12 -0.14 0.00E+0005.00E+0081.00E+0091.50E+0092.00E+0092.50E+0093.00E+009
Frequency (Hz)
Fig. 7a: Frequency dependence of dielectric Tan loss of the synthesized samples Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0 and 0.4) at Room temperature
0.04 0.02
Dielectric Loss Factor
x=0.6 0.00 -0.02
1.0
0.8
-0.04
x=0.8
0.6
0.4
-0.06 0.2
-0.08
0.0
0.00E+000
5.00E+008
1.00E+009
1.50E+009
2.00E+009
2.50E+009
3.00E+009
-0.10 -0.12 0.00E+0005.00E+0081.00E+0091.50E+0092.00E+0092.50E+0093.00E+009
Frequency (Hz)
Fig. 7b: Frequency dependence of dielectric tan loss of the Ca0.5Sr0.5Fe10.8Zr0.6Cu 0.6O19 and inset represents the Frequency dependence of dielectric tan loss of the Ca0.5Sr0.5Fe10.4Zr0.8Cu0.8O19 at Room temperature
1.20E-01
2.00E+01
1.00E-01 8.00E-02
1.50E+01 6.00E-02 1.00E+01 4.00E-02 5.00E+00
2.00E-02
0.00E+00
0.00E+00 0
Dielectric Loss
Dielectric Constant
2.50E+01
Dielectric constant Dielectric loss
0.2 0.4 0.6 0.8
Conc. of dopants
Fig. 8 Composition dependence of (Ɛ’ & Ɛ") of the synthesized compounds Ca0.5Sr0.5Fe122xZrxCu xO19 (x=0.0-0.8) at Room temperature
x=0.0 x=0.4
0.30 0.25 0.20 0.15
Conductivity
0.10 0.05 0.00 -0.05 -0.10 -0.15 -0.20 -0.25 0.00E+0005.00E+0081.00E+0091.50E+0092.00E+0092.50E+0093.00E+009
Frequency (Hz)
Fig. 9a: Frequency dependence of conductivity of the samples Ca0.5Sr0.5Fe122xZrxCu xO19 (x=0.0 and 0.4) at Room temperature
x=0.6 0.0004
x=0.8
0.0002 0.0000
4
-0.0002 -0.0004 -0.0006
Conductivity
-0.0008 -0.0010 -0.0012 -0.0014
2
-0.0016 0.00E+0005.00E+0081.00E+0091.50E+0092.00E+0092.50E+0093.00E+009
0
0.00E+0005.00E+0081.00E+0091.50E+0092.00E+0092.50E+0093.00E+009
Frequency (Hz)
Fig. 9b: Frequency dependence of conductivity of Ca0.5Sr0.5Fe10.8Zr0.6Cu 0.6O19 and inset represents the Frequency dependence of conductivity of the Ca0.5Sr0.5Fe10.4Zr0.8Cu 0.8O19 at Room temperature
1.20E-04
2.50E-02
1.00E-04
2.00E-02
8.00E-05
1.50E-02
6.00E-05
1.00E-02
4.00E-05
5.00E-03
2.00E-05
0.00E+00
0.00E+00 0
Conductivity
Dielectric Tan Loss
3.00E-02
Dielectric tan loss Conductivity
0.2 0.4 0.6 0.8
Conc. of dopants
Fig. 10: Composition dependence of dielectric tan loss & conductivity of the synthesized compounds Ca0.5Sr0.5Fe12-2xZrxCuxO19 (x=0.0-0.8) at Room temperature
Table 1
Magnetic parameters calculated from the hysteresis loops of the synthesized compounds
Ca0.5Sr0.5Fe122xZrxCuxO19 Saturation Magnetization (emu/g) Remanence (emu/g) Coericivity (Oe) Squareness ratio Mr/2
x=0.0
x=0.2
x=0.4
x=0.6
x=0.8
34.477
29.627
27.132
25.133
23.835
11.593
10.136
9.894
9.721
8.352
681.81
738.80
716.67
679.09
623.97
0.33
0.34
0.36
0.38
0.35
5.79
5.06
4.94
4.86
4.17
Research Highlights
Particle size of these samples is suitable for high density recording media. The samples have coericivity suitable for longitudinal magnetic recording media. The sample (x=0.8) has dielectric constant useful for high frequency applications.
