BaM/YIG nano composites A microwave material for C to U band application BaM/YIG nano composites A microwave material for C to U band application Vipul Sharma, Sweta Kumari, and Bijoy Kumar Kuanr Cita[.]
BaM/YIG nano-composites: A microwave material for C to U band application Vipul Sharma, Sweta Kumari, and Bijoy Kumar Kuanr Citation: AIP Advances 7, 056417 (2017); doi: 10.1063/1.4974495 View online: http://dx.doi.org/10.1063/1.4974495 View Table of Contents: http://aip.scitation.org/toc/adv/7/5 Published by the American Institute of Physics Articles you may be interested in Design and analysis of a 3D-flux flux-switching permanent magnet machine with SMC cores and ferrite magnets AIP Advances 7, 056632056632 (2017); 10.1063/1.4974524 AIP ADVANCES 7, 056417 (2017) BaM/YIG nano-composites: A microwave material for C to U band application Vipul Sharma,1 Sweta Kumari,2 and Bijoy Kumar Kuanr1,a Special Central Centre for Nano Science, Jawaharlal Nehru University, New Delhi 110067, India University of Jharkhand, Jharkhand, India (Presented November 2016; received 23 September 2016; accepted 28 October 2016; published online 17 January 2017) Hexaferrites have become important candidates for a variety of microwave and millimeter wave devices due to their large uniaxial magneto-crystalline anisotropy and high saturation magnetization The goal of the present investigation is to synthesize Barium hexaferrite/Yttrium Iron Garnet (BaFe12 O19 /Y3 Fe5 O12 ): (BaM/YIG) Nano-Composites (NCs) to be used in broad band microwave frequency range applications, especially as microwave absorber X-ray diffractometry, Vibrating Sample Magnetometer (VSM), and ferromagnetic resonance (FMR) techniques were used to characterize these NCs Using a Cu coplanar wave guide and a Vector Network Analyzer, broadband (C to U) microwave absorption were investigated by placing the bulk sample in flip chip mode Various mathematical models were employed to fit the experimental data to yield intrinsic and extrinsic damping parameters © 2017 Author(s) All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/) [http://dx.doi.org/10.1063/1.4974495] I INTRODUCTION Today the need for creating composite materials is not limited in just magnets but also used in electronic devices such as magnetic recorder, microwave absorber etc Microwave-absorbing materials have gained immense interest to the scientists and technologists due to their usage in military application and also for civilian use Microwave absorbing materials could be used in stealth defense system The radar cross-section of target scan effectively reduces by use of the absorbers The potential advantages of these materials are related to environmental pollution caused by the Electromagnetic Interference (EMI) due to vast use of electronic equipment, computerized networks, cell phones etc.1–7 The composites having hard and soft phases have attracted many scientific and technological interest in past few years due to their applications in permanent magnets, microwave devices and data-storage systems.1–5 The use of ferrites in present study is important because the penetration of em waves is possible in ferrites because they are non-conducting in nature In contrast it is limited in metals because of the skin effect Ferrites are treated as best material for a variety of electronic applications due to their low eddy current loss Because of its large uniaxial magneto-crystalline anisotropy energy BaM is a suitable candidate for millimeter –wave devices applications.6 With the appropriate material substitutions, the saturation magnetization and the effective anisotropy field may be varied for device operation over a wide range of frequencies However large magnetic losses hinder the use of these materials in resonant devices Our objective was to reduce the coercivity of BaM so that it can be used to absorb microwave frequencies beyond X band and work at least up to till 40 GHz range One way is to reduce coercivity and hence FMR resonance linewidth is to synthesize composite of hard-soft ferromagnetic materials YIG is the best suited soft material for this due to its almost zero coercivity and relatively low a Email: bijoykuanr@mail.jnu.ac.in 2158-3226/2017/7(5)/056417/6 7, 056417-1 © Author(s) 2017 056417-2 Sharma, Kumari, and Kuanr AIP Advances 7, 056417 (2017) saturation magnetization The interaction of hard and soft phase also gives rise to exchange couple effect So this material can also be used in application where exchange coupling effect is required, such as to boost the usable frequency of the microwave absorbers Various nano-composites have been prepared using soft and hard magnetic material but their maximum absorption frequency lies only up to X band.7,8 The nanocomposite materials synthesized in the present study can effectively absorb electromagnetic waves up to Ka- (26 - 40 GHz) frequency band II EXPERIMENT To prepare (BaM)1-x (YIG)x (x varies from 0.0 to 1.0) nano composites an one step sol-gel method was used Two different sols; one for BaM and other for YIG with proper stoichiometric amount were prepared Barium Nitrate (Ba(NO3 )2 ) and Ferric Nitrate nonahydrate (Fe(NO3 )3 9H2 O) (Sigma Aldrich, 99.99%) were used for BaM (BaFe12 O19 ), and Yttrium nitrate (Y(NO3 )3 ) and Fe(NO3 )2 9H2 O were used for YIG(Y3 Fe5 O12 ) Citric acid was used as a chelating agent to combine the complex structure Sols were prepared with DI water as a solvent After mixing them for hour the sol of YIG was added slowly into BaM sol and a homogenous mixture containing BaM and YIG sol was obtained This mixture was then heated under infrared lamp The dry powder was then heated again on a hot plate till all the moisture evaporates from the sample Then these powder were annealed in air at 11000 C for hours at 20 C/min The ratio of Ba:Fe was taken 1:12 in BaM The annealed powder was pressed to form pellets of same size (10 mm diameter) and thickness (0.4 mm) Different composition of (BaM/YIG) nanocomposites were prepared similarly as above mentioned procedure A Characterization techniques X-ray diffraction of powder samples were performed at room temperature using Cu-Kα Radiation (λ = 1.5418A◦ ) in Miniflex Rigaku instrument The magnetic characterization was done at room temperature using vibrating sample magnetometry probe used in Physical Property Measurement System (PPMS) from Cryogenic Ltd The JEOL 2100F Transmission electron microscope was used for analysing nanoparticles size A dispersion of NPs was made in ethanol and then a drop of the nanoparticles dispersion liquid was put on the carbon coated cu grid and (ethanol) was allowed to dry in air This grid was used in TEM The ferromagnetic resonance (FMR) experiments were done using a broad-band FMR system in transmission mode - frequency range from C- to Ka- band and magnetic field from to 15 kOe using a Keysight Inc (PNA - N5224A) Vector Network Analyzer (VNA) The bulk sample was placed on a cu-coplanar waveguide in flip chip manner and transmission scattering parameters (S21 ) were measured All the measuring probes were calibrated using TRL calibration for 50 ohm matching impedance to the VNA We have used a computer controlled program to sweep the magnetic field and recorded the S21 data from the VNA III RESULTS AND DISCUSSION The XRD Pattern of [(BAM)1-x (YIG)x ] NCs with x = 0.3 and 0.8 along with pure BaM and YIG are shown in Figure: 1(a) The XRD Pattern clearly shows the formation of composite phases as all the peaks of both the compounds are present and varying in intensity as the concentration of either of the compound is varying The peaks of BaM at [203] and [205] are disappearing completely from pure BaM to pure YIG while the peaks of YIG are growing such as peaks at [400] and [422] No other phase other than BaM and YIG is detected in the BaM/YIG composite XRD data The XRD results show the coexistence of hard phase (BaM) and soft phase (YIG) annealed at 1200 ◦ C showing good crystallinity with no impurity phase present The crystallite size (τ) was calculated using Scherrer’s formula: Nλ (1) τ= δcosθ where: N = shape factor, λ = x-ray wavelength (Cu Kα) λ = 1.54181 Å 056417-3 Sharma, Kumari, and Kuanr AIP Advances 7, 056417 (2017) FIG (a) The XRD Pattern of [(BaM)1-x (YIG)x ] NCs for x=0, 0.3, 0.8, 1.0, showing the evolution of lattice planes with change in composition of YIG (x) Figure 1(b) shows the TEM image of pure BaM Figure 1:(c) shows the TEM image of [(BaM)1-x (YIG)x ] NCs for x=0.5 Figure 1:(d) shows the VSM curve of [(BaM)1-x (YIG)x ] NCs for x=0 - 1, inset figure shows the variation in coercivity (Hc ) with change in composition x δ = line broadening at half the maximum intensity (FWHM) in radians θ = Bragg angle Crystallite size was calculated by fitting of all the peaks and taking average of all the sizes obtained The average particle size obtained for BaM and YIG doped BaM NCs increased from 35 nm to 37 nm respectively Figure 1(b) and (c) shows the TEM images of nanoparticles of pure BaM and [(BaM)1-x (YIG)x ] NCs for x=0.6 which are in close agreement with XRD data A Magnetic properties The room temperature magnetic hysteresis curves for different concentration of YIG in BaM/YIG nano-composite are shown in Figure 1(b) As the concentration of YIG decrease in BaM/YIG NCs, the VSM curve become more smooth showing the better interaction of hard and soft phases.9 The kinks in hysteresis loops appeared in (0.2BaM/0.8YIG) and with increasing BaM kinks disappeared This is due to somewhat less uniform distribution of hard and soft phase The uniformity increased with the concentration of BaM in the nanocomposite and the interaction between hard and soft phases also appeared to increase The coercivity (Hc ) and Magnetization (Ms ) decrease as the amount of soft phase (YIG) in the composition increased as shown in Figure 1(b) The increment in remanence magnetization (Mr ) from 150 Oe for YIG to 1738 Oe for 0.7BAM/0.3YIG can be attributed to the formation of mixed phase BaM/YIG NCs as both remanence magnetization (Mr ) and Coercivity (Hc ) of BaM are higher than YIG.10 B Microwave characterization Room temperature fixed frequency (from GHz – 36 GHz) FMR Measurements were performed in field sweep mode using cu-coplanar waveguide in flip chip geometry Resonance field (Hr) and field line width (∆H) were obtained from the calibrated S21 experimental data Figure 2(a) shows the differential FMR spectra in field sweep mode for (x=0.8) in [(BaM)1-x (YIG)x ] NCs, which clearly signify the resonance field and corresponding linewidth at each corresponding frequencies We have observed that there is an increase in absorption with the increase in frequency and is due to the increase 056417-4 Sharma, Kumari, and Kuanr AIP Advances 7, 056417 (2017) FIG (a) Differential FMR Spectra of [(BaM)1-x (YIG)x ] NCs for x=0.8 in field sweep mode for X-band to Ka-band; clearly showing the resonance field (Hr ) and linewidth (∆H) Figure 2:(b) Variation in resonance field and field linewidth as a function of frequency for (0.2BaM) (0.8YIG) in relative permeability (µr ) of the material which is directly related to the power absorption.11 For (BaM/YIG) nano composite the resonance magnetic field (Hr ) and field linewidth (∆H) observed to increase with the increase in frequency This is in agreement with the nanocomposite resonance relation.12 fr = γ(Hr + Hex + Ha − NMs ) (2) where, N = demagnetize factor, γ= gyromagnetic ratio, H ex = resonance field (KOe) We have also observed that with the decrease of saturation magnetization (Ms ) with increasing YIG concentration in (BaM/YIG) NCs, resonance field observed to decrease At a constant frequency, the decreasing Ms with almost constant magnetic anisotropy (Ha ) causes resonance field (Hr ) to decrease Figure shows the variation of resonance linewidth (∆H) as a function of frequency for [(BaM)1-x (YIG)x ] nano-composites with x=0.5, 0.6, and 0.8 The resonance linewidth (∆H) observed to increase with the increase in the concentration of BaM in the [(BaM)1-x (YIG)x ] nano-composites This effect is in accordance with the observation of increasing coercivity of (BaM/YIG) NCs with increasing BaM concentration, as observed in the VSM data The observed FMR linewidth are a combination of intrinsic as well as extrinsic contributions to linewidths Such linewidth responses are often interpreted in terms of a combined inhomogeneous broadening and Landau-Lifshitz or Gilbert damping model The experimental value of Gilbert damping can be deduced from the FMR linewidth ∆H using the phenomenological expression; FIG Shows the experimental and theoretical plots of FMR linewidth of [(BaM)1-X (YIG)X ] nanocomposite (a), (b), and (c) parts show plot for different values of x Inset of each figure shows the values of different parameters derived from the fitted using equation (3) and (4) Blue dots represent the experimental data 056417-5 Sharma, Kumari, and Kuanr AIP Advances 7, 056417 (2017) ∆H = ∆H0 + 4παf γ µ0 (3) where ∆H0 is the linewidth at zero frequency - a measure of the inhomogeneous broadening (extrinsic linewidth) α √ is the parameter which determines how much the linewidth changes with frequency The factor 2/ assumes Lorentzian line shape of the resonance absorption curve The fitting of experimental data to the phenomenological expression given in eq (2) are shown as dotted lines in the graphs of Figure It is found that with the increase of x in the [(BaM)1-x (YIG)x ] NCs there is an increase of gyromagnetic ratio γ = γ 2π It is 2.4 GHz/kOe for pure YIG and increased to 3.0 GHz/kOe for pure BaM nanoparticles It is also observed that with the increase of x, ∆H0 the inhomogeneous broadening (extrinsic linewidth) increased It is smallest for pure YIG (0.28 kOe) and is found to be largest for pure BaM (0.9 kOe) nanoparticles The fitting to eq (3) produce a linear dependence of linewidth to frequency But it is clear from Figure 3(a – c) [also from the remaining data for x values which are not included in this paper due to space limitations] that the observed ∆H values not follow a linear dependency as predicted by the phenomenological Landau-Lifshitz damping expression given in eq (3) The macroscopic feature of the linewidth mechanism responsible for the non-linear frequency dependence of FMR linewidth, is the transient magnetization configuration owing its existence to the extrinsic stresses generic to the BaM/YIG nanocomposites The effective damping constant is a combination of intrinsic and extrinsic values, whose magnitudes are deduced from the frequency dependence of FMR linewidth As proposed by Bastrukov et.al.,13 the FMR linewidths are fitted with the following micromagnetic model consisting of intrinsic (α) and ( β) damping parameters Hence both the intrinsic and extrinsic damping contributions to linewidth are taken care of The expression to linewidth can be expresses as; 4πf ∆H = γ µ0 ! 21 α − β − γ µ Ms 2πf (4) Where, ∆H = FMR Linewidth f = Ferromagnetic Resonance Frequency γ = gyromagnetic ratio α = Intrinsic damping parameter β = Extrinsic damping parameter Ms = Saturation magnetization µ0 = Permeability of free space The above fitting model using equation (4) are employed for (BaM)/(YIG) nanocomposites with different values of x (different composition) to derive γ, α, and β parameters The extrinsic [(β)] and intrinsic [(α)] Gilbert damping constant depends on the composition of (BaM)/(YIG) The extrinsic contribution to linewidth ( β value) increases (Table I) from 0.03 for pure YIG NPs to 0.1 for pure BaM NPs The value of β also found to increase with increase of x in [(BaM)1-x (YIG)x ] NCs; 0.032 for 20% BaM to 0.09 for 50% BaM in (BaM/YIG) NCs Similarly, the intrinsic contribution to linewidth TABLE I Various parameters derived from the fitting to eq (3) and (4) for the FMR linewidth data YIG LLG Model fitting β α γ (GHz/kOe) ∆H0 (kOe) 0.0012 2.40 0.28 YIG Extrinsic damping Fitting 20BaM LLG Model fitting 20BaM Extrinsic damping Fitting 40BaM LLG Model fitting 40BaM Extrinsic damping Fitting 50BaM LLG Model fitting 50BaM Extrinsic damping Fitting 0.03 02 2.54 0037 2.97 0.34 032 032 2.91 - 0105 2.975 0.445 042 047 3.0 - 026 2.83 0.88 090 084 3.0 - 056417-6 Sharma, Kumari, and Kuanr AIP Advances 7, 056417 (2017) [(αvalue)] also increased from 0.02 for pure YIG NPs to 0.1 for pure BaM NPs For intermediate values of x in [(BaM)1-x (YIG)x ] NCs α also observed to increase with the increase of x IV CONCLUSION The synthesis of BaM/YIG nano composites (NCs) with varying concentration of two compounds was successfully synthesized using one step sol gel method XRD and VSM results shows that hard phase BaM and soft phase YIG can coexist together as a single phase Very wide frequency band remarkable electromagnetic properties were achieved in [(BaM)1-x (YIG)x ] NCs which can be useful for microwave/mm-wave signal processing devices, with operational frequency as high as 35 GHz with an applied field of Tesla The decreasing coercivity for the NCs by the addition of YIG allows hard-type BaM to achieve lower FMR linewidth in comparison to pure BaM To verify the linewidth experimental results, we have used two different analytical models to derive the intrinsic and extrinsic contribution to Gilbert damping parameters ACKNOWLEDGMENTS We acknowledge AIRF, JNU for the PPMS facility used in this work The grant support of DST India through DST-Purse program is highly acknowledged X Shen et al., J Am Ceram Soc 95, 3863 (2012) Tyagi, H B Baskey, R C Agarwala, V Agarwala, and T C Shami, Ceram Int 37, 2631 (2011) L G Yan, J B Wang, X H Han, Y Ren, Q F Liu, and F S Li, Nanotechnology 21, 095708 (2010) R C Pullar, J D Breeze, and N M Alford, J Am Ceram Soc 88, 2466 (2005) X H Guo, Y H Deng, D Gu, R C Che, and D Y Zhao, J Mater Chem 19, 6706 (2009) Y Y Song et al., Appl Phys Lett 97, 173502 (2010) X L Dong, X F Zhang, H Huang, and F Zuo, Appl Phys Lett 92, 013127 (2008) W L Song, M S Cao, Z L Hou, J Yuan, and X Y Fang, Scripta Mater 61, 201 (2009) S Hazra and B Kumar Ghosh, RSC Adv 4, 45715 (2014) 10 M Liu, H Yang, Y Lin, and Y Yang, Mater Res Bull 10, 195 (2014) 11 L Zhang, X D Su, Y Chen, Q FLi, and V G Harris, Scr Mater 63, 492 (2010) 12 B Kuanr et al., IEEE Trans Magn 41, 3538 (2005) 13 B Sergey et al., e-print arXiv:1210.2609v1 (2012) S ...AIP ADVANCES 7, 056417 (2017) BaM/YIG nano- composites: A microwave material for C to U band application Vipul Sharma,1 Sweta Kumari,2 and Bijoy Kumar Kuanr1 ,a Special Central Centre for Nano. .. characterize these NCs Using a Cu coplanar wave guide and a Vector Network Analyzer, broadband (C to U) microwave absorption were investigated by placing the bulk sample in flip chip mode Various... microwave frequency range applications, especially as microwave absorber X-ray diffractometry, Vibrating Sample Magnetometer (VSM), and ferromagnetic resonance (FMR) techniques were used to characterize