Study on the Gilbert damping of polycrystalline YIG films with different capping layers

Current Applied Physics 20 (2020) 167–171

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Study on the Gilbert damping of polycrystalline YIG films with different capping layers

T

Satya Prakash Pati1 Department of Electrical Engineering, Graduate School of Engineering, Tohoku University, Japan

A R T I C LE I N FO

A B S T R A C T

Keywords: YIG Thin films Ferromagnetic resonance Gilbert damping Magnetization dynamics

This paper describes the effect of 5-nm thick platinum (Pt), aluminum (Al) and silicon oxide (SiOx) capping layers on the static and dynamic magnetic properties of 400-nm thick polycrystalline YIG films deposited on a Pt buffer layer. Both static and dynamic magnetic properties of Pt capped YIG film are totally different among all YIG films. Namely, the squareness of the magnetization curve for Pt capped YIG film increases, indicating that Pt capped YIG film is magnetically softer than other YIG films. Interestingly, the effective Gilbert damping parameter of Pt capped YIG films is about four times as large as those of other YIG films, and its value is approximately 9.52 × 10−4. However, the value of Gilbert damping is 2.55 × 10−4, 3.46 × 10−4 and 3.85 × 10−4 respectively for no capping, SiOx capping and Al capping samples respectively. This huge change in Gilbert damping parameter is mainly originating from the spin pumping effect, which arises at the interface of a material having strong spin orbit interaction such as Pt. Moreover, the enourmous increase in the value of effective anisotropic field and decrese in effective saturation magnetization indicates interface anisotropy is induced in Pt capped sample. These results suggest that the static and dynamic magnetic properties of YIG film can be controlled by selecting an appropriate capping layer.

1. Introduction Garnets and ferrites, with controllable magnetic properties have wide range of potential applications including microwave devices such as resonators, isolators, circulator, wavelength accordable filters etc [1,2]. Among all, yittrium-iron-garnet (YIG), Y3Fe5O12 has been playing most prominent role in understanding high frequency magnetization dynamics since its discovery in 1950s [3,4]. Owing to its unique properties such as ultralow damping, high Curie temperature, electrically insulator etc, it is widely used in ferromagnetic resonance experiments [5–10], research on magnonics [11–18] and magnon based Bose-Einstein condensates [19–22], spin-pumping [23–27] and investigation of inverse spin hall effect [5,23,28–32]. Typically, the growth of YIG films on single-crystal gadolinium gallium garnet (GGG) substrates has been reported due to similar crystal structure and extremely small lattice mismatch between YIG and GGG [33–36]. However, certain device application demands the growth of YIG films on metals; for example, a bottom electrode is required under the active layer in coupled-line and strip-line type devices [37–39]. The growth of YIG films on metals becomes one of the challenging subjects due to many reasons such as; the oxidation, the interface diffusion, the breakup of the metallic films, and so on, restrict the realization of high

1

quality YIG films on metals. Until now, we reported the effective Gilbert damping (α) of YIG films deposited over the platinum (Pt) buffer layer decreases markedly, which is attributed to the modification of microstructure by a Pt buffered layer [40]. On the other hand, the control of Gilbert damping by materials or interface modification is one of the extensive researches in spintronics and magnonics for practical application such as high speed information storage devices [41,42]. One of efficient methods for the control of α is the “spin-pumping effect” [23–27], where a pure spin-current (JS,pump) from a ferromagnetic (FM) layer injects into an adjacent nonmagnetic (NM) layer leading to an additional damping to the magnetization precision. The dissipation of the spin current in the NM layer depends on its electronic structure such as the spin-orbit interaction (SOI). There are many ongoing debates on the other external parameters effecting spin current dissipation induced Gilbert damping e.g. an interfacial spin resistance, a proximity induced spin polarization, a magnetic dead layer at interface etc. Although the spin-pumping effect at YIG/Pt interface, comprising single crystalline YIG has been extensively studied, but a few report on the polycrystalline YIG is available. The advantages of study on polycrystalline film is allowing it's wide range of applicability as it can be grown on any substrate or electrode. Herein, we investigated the static and dynamic magnetic properties

E-mail address: [email protected]. Presently at: Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464–8602, Japan.

https://doi.org/10.1016/j.cap.2019.10.022 Received 22 April 2019; Received in revised form 16 October 2019; Accepted 29 October 2019 Available online 31 October 2019 1567-1739/ © 2019 Korean Physical Society. Published by Elsevier B.V. All rights reserved.

Current Applied Physics 20 (2020) 167–171

S.P. Pati

of polycrystalline YIG films deposited on a Pt buffer layer with or without different capping layers, and then discussed about the influence of these layers on the Gilbert damping of YIG films.

magnetization (4πMs) for all YIG films remains almost same as the bulk value (1733 G). The value of coercivity lowers and the squareness (remanence ratio, Mr/Ms) strengthens subsequently for the Pt capped YIG film in comparison to other YIG films. The reason for the enhancement of in-plane remanence ratio is may be due to strong spin-orbit interaction of Pt capping layer which is responsible for further enhancement of interface anisotropy. Theoretical calculation on magneto-crystalline anisotropy suggests that the interface anisotropy can be enhanced by the hybridization between 3d orbital of transition metal and 4d orbital of heavy metal [43]. Proximity induced enhancement of interface anisotropy may be another reason for the enhancement of remanence ratio. Similar picture from FMR results was obtained which was discussed in next section. Where, effective anisotropic field is substantially increased and effective saturation magnetization is decresed for the Pt capped sample in comparison to other capped samples. A microscopic theory of spin relaxation anisotropy in graphene with proximity-induced spin-orbit coupling was also reported recently by Offidani et al. [44]. On the basis of these results, it can be pointed out that a Pt capping layer mainly plays one of the important roles for magnetic softening of YIG films. To understand the effect of capping layer on dynamic magnetic properties of YIG films deposited on the Pt buffer layer, the FMR spectra of all YIG films were measured by the broadband FMR measurement with the CPW and the VNA. S-parameters of the CPW on which a film is set were measured while sweeping the external magnetic field (Hex) between −100Oe to 3000Oe in an individual frequency (fres) range between 1 and 9 GHz. Fig-3 represents the typical FMR spectra of samples recored at fres of 5 GHz with different capping layers. Every FMR peak observed at each fres was fitted with Lorentzian function to obtain both the resonance field (Hres) and the line-width (ΔHres). The effective in-plane anisotropy field (Hk,eff) and effective saturation magnetization (4πMs,eff) were obtained from the (fres)2 vs. Hres plots (Fig. 4) which are assumed as fitting parameters in Kittel's formula [45].

2. Experimental details Our film structures are c-Al2O3 (sub)/Pt (25 nm)/YIG (400 nm) or cAl2O3 (sub)/Pt (25 nm)/YIG (400 nm)/X (5 nm) (X is capping layer and is Pt, Al, SiOx). 25-nm thick Pt buffer layer was deposited by a DC magnetron sputtering for controlling the microstructure of YIG film. Fabrication of YIG films was described elsewhere [40]. Metal capping layers were fabricated by a DC magnetron sputtering whereas oxide capping layer was done by a RF sputtering. For YIG fabrication, a RF magnetron sputtering at room temperature (RT) was employed with a base pressure of ~4.0 × 10−4 Pa and RF power of 180 W. YIG deposition was performed in a mixed gas of Ar/O2 in proportion of 3.8: 1.2 SCCM. Maintaining the rate of deposition as 2.17 nm/min. The as-deposited amorphous YIG films were recrystallized by annealing at 900 °C in air for 3 h. As for static magnetic properties of the films are concerned, the inplane magnetization (M−H) curves were measured with a vibrating sample magnetometer (VSM). On the other hand, for the dynamic magnetic properties of the films, the damping parameter of the films were estimated by a broadband ferromagnetic resonance measurement using a coplanar wave guide (CPW) and a vector network analyzer (VNA). The CPW having a trilayer structure of Cr/Cu/Cr was fabricated on a glass substrate and capped with SiO2 layer. To get a characteristic impedance Z0 for the CPW of ~50-Ω, the signal line, gap, and ground line widths were designed as 10, 2.5, and 17.5 μm, respectively,. The length of the CPW was 2 mm. As demonstrated in Fig-1, the sample was kept upside down on the CPW and the reflection RF power (S11 parameter) was measured while sweeping the in-plane magnetic field at various frequencies of microwave applied through VNA. All the measurements were performed at room temperature.

γ 2 2 f Res = ⎛ ⎞ (Hk, eff + Hres )(4πMs, eff + Hres ), ⎝ 2π ⎠

3. Results and discussion

(1)

where γ is the gyromagnetic ratio. As can be seen in table-2, Hk,eff for the Pt capped YIG film was largest among all YIG films and its value was approximately 343 Oe, which may be ascribed to magnetic softness. The value of 4πMs,eff for none, SiOx, Al and Pt capped YIG possesses 1010.2, 936.6, 964.8 and 543.6 G respectively. Pt capped YIG film exhibits much lower value of 4πMs,eff than those for other films and bulk value (1733 G), meaning that the demagnetizing field in the perpendicular direction of film weakens markedly. In the case of homogeneous magnetization, energy of the system is equal to the sum of the anisotropy energy, demagnetizing energy and the energy in an external field:

The in-plane magnetization (M-H) curves of all YIG films are shown in Fig-2. Each shape of M-H curves for no-capped, SiOx, and Al capped YIG films are very similar, indicating the magnetization of these films becomes random in the direction of in-plane external magnetic field. On the other hand, the shape of M-H curve for Pt capped YIG films is dependent of in-plane external magnetic field, suggesting that the static magnetic property of this film is close to be more soft than those of other YIG films. To verify the static magnetic properties of all YIG films in details, magnetic parameters estimated from the in-plane M-H curves of all YIG films are summarized in table-1. The value of saturation

E= K sin2θ + 2πMs2 cos 2θ − Ms Hsinθ

(2)

where angle θ indicates the deviation of the magnetization from easy axis of anisotropy. Minimization leads to the expression:

sinθ =  

H

(

2K Ms

− 4πMs

)

(3)

where 2K/Ms is the anisotropy field, Hk. Ms vector “lies” to the plane when θ = 90 deg., i.e. when H reaches a value of Hs ≈ Hk–4πMs. If Hk < 4πMs, the Ms vector lies in initial state in the film plane, and for its translation to the perpendicular state, it is necessary to apply a field Hs = 4πMs–Hk in the normal direction to the film plane. Hence, the difference in the value of 4πMs and Hk represents the amount of field required to align 90 deg from the initial state of magnetization. To elucidate more about the effect of the different capping layer on the effective Gilbert damping parameter (αeff) of YIG films, which can be calculated directly from the slope of ΔHres versus fres plot by the following relation,

Fig. 1. Schematic representation of broadband CPW-FMR experimental geometry, where sample was put upside down on the CPW and reflection RF power (S11 parameter) was measured by a VNA. 168

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Fig. 2. In-plane M-H loops of 25-nm Pt buffered YIG (400 nm) films (a) without the capping layer and (b)–(d) with the capping layer; ((b) SiOx, (c) Al, and (d) Pt). Table 1 The saturation magnetization (Ms), coercivity (Hc) and squareness (or remanence ratio, Mr/Ms) evaluated from the in-plane magnetic hysteresis (M-H) loops for all YIGfilms. Capping Layer (X)

No capping

SiOx

Al

Pt

4πMs [G] Hc [Oe] Mr/Ms

1637 18.9 0.446

1727 20.4 0.507

1778 17.7 0.518

1675 1.2 0.776

ΔHres = ΔHres (0) +

4πα eff γ

fres ,

(4)

where ΔHres (0) represents the inhomogeneous broadening in a zero field (the anisotropy dispersion condition). Fig. 5 shows the FMR linewidth (ΔHres) as a function of fres for 25-nm Pt buffered YIG (400 nm) films without and with 5-nm thick capping layers (SiOX, Al, and Pt). Each value of ΔHres (0) was estimated as approximately 67.1, 82.6, 108.2, and 130.8 Oe for non, SiOX, Al and Pt capped YIG films, respectively. These differences mean that the magnetic inhomogeneities such as anisotropy dispersion and other effects [46–48] are enhanced by selecting capping layers. The value of ΔHres of Pt capped sample increases enormously at all frequency ranges in comparison with other samples. For example, ΔHres at 5 GHz for the Pt capped YIG film broadened and its value was approximately 154 Oe. Whereas, ΔHres at 5 GHz for other YIG films are sharp and their values were approximately 80–115 Oe. As can be noticed in Fig. 5, the slope for the Pt capped YIG film was steepest among all YIG films, indicating that αeff becomes large in comparison with other YIG films. The value of αeff deduced from the slope was 2.55, 3.46, 3.85 and 9.52 × 10−4 for none, SiOx, Al and Pt capped YIG films,

Fig. 3. Typical FMR spectra at 5 GHz of YIG films having (a) no capping layer (b) SiOx capping layer (c) Al Capping layer and (d) Pt capping layer respectively. An enhancement in line width is observed in case of Pt-capped YIG films.

respectively. Namely, the value of αeff for the Pt capped YIG film was much higher, while the value of αeff for other YIG films were almost same. This difference may be originated from the interfacial effect like spin-pumping. Our previous report on enhanced Gilbert damping at low temperature in YIG/Pt interface was explained due to interfacial in origin [49]. In case of spin-puming effect, the spin current (JS,pump) 169

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Fig. 4. In-plane external magnetic field (Hex) dependent ferromagnetic resonance frequency (f2Res) and corresponding fitting with Kittel's equation of Pt 25 nm buffered YIG (400 nm) film with (a) No Capping, (b)SiOx capping,(c) Al capping, and (d) Pt Capping respectively. Table: 2 The effective anisotropy field (Hk,eff), effective saturation magnetization (4πMs,eff), inhomogeneous broadening at zero field (ΔHres (0)) and effective Gilbert damping parameter (α) of various capped YIG (400 nm) films deposited on the 25-nm thick Pt buffer layers. Capping Layer

No capping

SiOx

Al

Pt

Hk,eff [Oe] 4πMs,eff [G] ΔHres (0)[Oe] αeff (10−4)

150.7 1010.2 67.1 2.55

179.3 936.6 82.6 3.46

184.8 964.8 108.2 3.85

343.3 543.6 130.8 9.52

generated from the magnetization precision driven by FMR can dissipate in an adjacent NM capping layer. The dissipation of the spin current depends on the spin diffusion length of capped layers: In case of the Pt capped YIG film, the JS,pump quickly dissipate inside Pt layer due to shorter spin diffusion length (λsf) [50]. Therefore, αeff increases markedly. In contrast, λsf is comparatively larger for other capped YIG films, resulting the values of αeff are almost as same as that of noncapped YIG film. Here, Pt acts as a perfect spin sink material due to strong spin-orbit interaction. Moreover, the contribution of radiative damping (αrad) arising from the induced eddy current in Pt/Al capping layer cannot be denied. Unlike eddy current damping (αeddy) that arrises from the eddy current of the CPW, the αrad depends on the dimension and properties of both CPW and sample, which can be expressed as

αrad =

Fig. 5. FMR linewidth (ΔH) as a function of resonancefrequency (fRes) and corresponding linear fitting for 25-nm thick Pt buffered YIG (400 nm) films without a capping layer and with a X capping layer (X = SiOx, Al, and Pt).

μ02 Ms γηtl 2Z0 W

dimensionless parameter that accounts for the mode profile in the sample. Z0 and W are impedance and width of the conductor, respectively [51]. The value of αrad can be reduced in a sample by increasing

(5)

where, l is the sample length, γ is the gyromagnetic ratio, and η is a 170

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distance from the CPW, however one should take care of the reduction in amplitude of the FMR signal. The investigation of αrad contribution into αeff is significant in case of low damping material. However, the observed value of αeff in our case varies from sample to sample and becomes higher in case metal (Al and Pt) capped YIG films. Hence, we suspect that radiative damping also plays an important role here in addition to spin-pumping effect. Furthermore, αrad also depends on the resistance of capping layer. Capping layer having lower resistance should show higher αrad. Recently, Qaid et al. [52] investigated radiative damping at the interface of YIG/Pt and found to be ≈ 8 × 10−5 which is too low to distinguish if present in our sample. As a consequence, these discussions suggest that the effective Gilbert damping of YIG film can be controlled by selecting an appropriate capping layer with tunable spin diffusion length.

Appl. Phys. 115 (2014) 17A501. [7] Y. Sun, Y. Song, H. Chang, M. Kabatek, M. Jantz, W. Schneider, M. Wu, H. Schultheiss, A. Hoffmann, Appl. Phys. Lett. 101 (2012) 152405. [8] Y. Sun, H. Chang, M. Kabatek, Y. Song, Z. Wang, M. Jantz, W. Schneider, M. Wu, E. Montoya, B. Kardasz, B. Heinrich, S.G.E. teVelthuis, H. Schultheiss, A. Hoffmann, Phys. Rev. Lett. 111 (2013) 106601. [9] S.A. Manuilov, A.M. Grishin, J. Appl. Phys. 108 (2010) 013902. [10] S.A. Manuilov, S.I. Khartsev, A.M. Grishin, J. Appl. Phys. 106 (2009) 123917. [11] A.V. Chumak, A.A. Serga, B. Hillebrands, Nat. Commun. 5 (2014) 4700. [12] H. Kurebayashi, O. Dzyapko, V.E. Demidov, D. Fang, A.J. Ferguson, S.O. Demokritov, Nat. Mat. 10 (2011) 660. [13] A.B. Ustinov, A.V. Drozdovskii, B.A. Kalinikos, Appl. Phys. Lett. 96 (2010) 142513. [14] M. Inoue, A. Baryshev, H. Takagi, P.B. Lim, K. Hatafuku, J. Noda, K. Togo, Appl. Phys. Lett. 98 (2011) 132511. [15] H. Yu, O. d Allivy Kelly, V. Cros, R. Bernard, P. Bortolotti, A. Anane, F. Brandl, R. Huber, I. Stasinopoulos, D. Grundler, Sci. Rep. 4 (2014) 6848. [16] K. Bi, Y. Guo, X. Liu, Q. Zhao, J. Xiao, M. Lei, J. Zhou, Sci. Rep. 4 (2014) 7001. [17] S.O. Demokritov, A.A. Serga, V.E. Demidov, B. Hillebrands, M.P. Kostylev, B.A. Kalinikos, Nature 426 (2003) 159. [18] A.V. Chumak, V.S. Tiberkevich, A.D. Karenowska, A.A. Serga, J.F. Gregg, A.N. Slavin, B. Hillebrands, Nat. Commun. 1 (2010) 141. [19] F. Li, W.M. Saslow, V.L. Pokrovsky, Sci. Rep. 3 (2013) 1372. [20] P. Nowik-Boltyk, O. Dzyapko, V.E. Demidov, N.G. Berloff, S.O. Demokritov, Sci. Rep. 2 (2012) 482. [21] S.O. Demokritov, V.E. Demidov, O. Dzyapko, G.A. Melkov, A.A. Serga, B. Hillebrands, A.N. Slavin, Nature 443 (2006) 430. [22] A.A. Serga, V.S. Tiberkevich, C.W. Sandweg, V.I. Vasyuchka, D.A. Bozhko, A.V. Chumak, T. Neumann, B. Obry, G.A. Melkov, A.N. Slavin, B. Hillebrands, Nat. Commun. 5 (2014) 3452. [23] K. Ando, S. Watanabe, S. Mooser, E. Saitoh, H. Sirringhaus, Nat. Mat. 12 (2013) 622. [24] C. Burrowes, B. Heinrich, B. Kardasz, E.A. Montoya, E. Girt, Yiyan Sun, YoungYeal Song, M. Wu, Appl. Phys. Lett. 100 (2012) 092403. [25] M.B. Jungfleisch, V. Lauer, R. Neb, A.V. Chumak, B. Hillebrands, Appl. Phys. Lett. 103 (2013) 022411. [26] S.M. Rezende, R.L. Rodríguez-Suárez, M.M. Soares, L.H. Vilela-Leão, D. Ley Domínguez, A. Azevedo, Appl. Phys. Lett. 102 (2013) 012402. [27] I. Žutić, H. Dery, Nat. Mat. 10 (2011) 647. [28] H. Sakimura, T. Tashiro, K. Ando, Nat. Commun. 5 (2014) 5730. [29] V. Castel, N. Vlietstra, J. Ben Youssef, B.J. van Wees, Appl. Phys. Lett. 101 (2012) 132414. [30] M. Schreier, G.E.W. Bauer, V.I. Vasyuchka, J. Flipse, K. Uchida, J. Lotze, V. Lauer, A.V. Chumak, A.A. Serga, S. Daimon, T. Kikkawa, E. Saitoh, B.J. van Wees, B. Hillebrands, R. Gross, S.T.B. Goennenwein, J. Phys. D Appl. Phys. 48 (2015) 025001. [31] Y. Kajiwara, K. Harii, S. Takahashi, J. Ohe, K. Uchida, M. Mizuguchi, H. Umezawa, H. Kawai, K. Ando, K. Takanashi, S. Maekawa, E. Saitoh, Nature 464 (2010) 262. [32] H.L. Wang, C.H. Du, Y. Pu, R. Adur, P.C. Hammel, F.Y. Yang, Phys. Rev. B 88 (2013) 100406. [33] M. Shone, Circuit Syst. Signal Process. 4 (1985) 89. [34] Y. Krockenberger, K.-S. Yun, T. Hatano, S. Arisawa, M. Kawasaki, Y. Tokura, J. Appl. Phys. 106 (2009) 123911. [35] S.A. Manuilov, A.M. Grishin, J. Appl. Phys. 108 (2010) 013902. [36] M. Wu, Nonlinear spin waves in magnetic film feedback rings, in: R. Camley, R. Stamps (Eds.), Solid State Physics, Academic, Burlington, 2011, pp. 163–224. [37] J. Mazur, M. Solecka, R. Poltorak, M. Mazur, IEE Proc. Microw. Antennas Propag. 151 (2004) 477. [38] B.K. Kuanr, D.L. Marvin, T.M. Christensen, R.E. Camley, Z. Celinski, Appl. Phys. Lett. 87 (2005) 222506. [39] B.K. Kuanr, Y.V. Khivintsev, A. Hutchison, R.E. Camley, Z.J. Celinski, IEEE Trans. Magn. 43 (2007) 2645. [40] S.P. Pati, M. Al-Mahdawi, Y. Shiokawa, M. Sahashi, Y. Endo, IEEE Trans. Magn. 53 (2017) 6101105. [41] A.V. Chumak, V.I. Vasyuchka, A.A. Serga, B. Hillebrands, Nat. Phys. 11 (2015) 453. [42] Y. Tserkovnyak, A. Brataas, G.E.W. Bauer, Phys. Rev. Lett. 88 (2002) 117601. [43] D.-S. Wang, R. Wu, A.J. Freeman, Phys. Rev. B. 48 (1993) 15886. [44] M. Offidani, A. Ferreira, Phys. Rev. B. 98 (2018) 245408. [45] C. Kittel, Phys. Rev. 73 (1948) 155. [46] B. Heinrich, J.F. Cochran, R. Hasegawa, J. Appl. Phys. 57 (1985) 3690. [47] J.J. Krebs, F.J. Rachford, P. Lubitz, G.A. Prinz, J. Appl. Phys. 53 (1982) 8058. [48] J.O. Rantschler, C. Alexander, J. Appl. Phys. 93 (2003) 6665. [49] S.P. Pati, Y. Endo, IEEE Trans. Magn. 55 (2019) 6100104 1-4. [50] M. Tokaç, S.A. Bunyaev, G.N. Kakazei, D.S. Schmool, D. Atkinson, A.T. Hindmarch, Phys. Rev. Lett. 115 (2015) 056601. [51] M.A.W. Schoen, J.M. Shaw, H.T. Nembach, M. Weiler, T.J. Silva, Phys. Rev. B 92 (2015) 184417. [52] M. Mohammad, Tim Richter Qaid, Müller Alexander, Hauser Christoph, Ballani Camillo, Schmidt Georg, Phys. Rev. B 96 (2017) 184405.

4. Conclusion In conclusion, the effect of different capping layers on static and dynamic magnetic properties of 400-nm thick YIG films deposited on 25-nm thick Pt buffer layer was investigated. These results were compared with the results obtained for non-capped YIG film. The in-plane anisotropy field is found to be largest for Pt capped sample among all which is corroborated with the highest squareness ratio of M-H curve. The effective saturation magnetization for the Pt capped YIG film was found to be lowest among all the YIG films, indicating that the demagnetizing field in the perpendicular direction of film weakens markedly. The value of effective Gilbert damping was enormously increased for the Pt capped YIG film, which was attributed to the spin pumping effect at the YIG/Pt capping layer interface. A strong spinorbit interaction material like Pt was responsible for such enhancement in Gilbert damping parameter. This result suggests that the static and dynamic magnetic properties of YIG film can be controlled by selecting an appropriate capping layer. Declaration of competing interest I declare that there is no conflict of interest associated with this paper. Acknowledgement I would like to thank JSPS for the international post-doctoral research fellowship (ID no: P17070). I am grateful to Prof. Masashi Sahashi of Tohoku University for providing RF and DC sputtering machine to fabricate YIG films and bottom electrode. I am also thankful to Associate Professor Yasushi Endo of Tohoku University for help during FMR and VSM measurements. The author would like to thank Prof. Osamu Kitakami, Associate Prof. Satoshi Okamoto, and Assistant Prof. Nobuaki Kikuchi at Tohoku University for performing the photo lithography. References [1] B. Lax, K.J. Button, Microwave Ferrites and Ferromagnetic, McGraw-Hill, Newyork, 1962. [2] M.P. Horvath, J. Magn. Magn. Mater. 215 (2006) 171. [3] F. Bertaut, F. Forrat, Compt. Rend. 242 (1956) 382. [4] S. Geller, M.A. Gilleo, Acta Crystallogr. 10 (1957) 239. [5] O. d Allivy Kelly, A. Anane, R. Bernard, J. Ben Youssef, C. Hahn, A.H. Molpeceres, C. Carrétéro, E. Jacquet, C. Deranlot, P. Bortolotti, R. Lebourgeois, J.-C. Mage, G. de Loubens, O. Klein, V. Cros, A. Fert, Appl. Phys. Lett. 103 (2013) 082408. [6] T. Liu, H. Chang, V. Vlaminck, Y. Sun, M. Kabatek, A. Hoffmann, L. Deng, M. Wu, J.

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