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1 Journal of the Korean Magnetics Society, Volume 20, Number 1, February 2010 DOI: /JKMS Vector Network Analyzer w Py œ yáw Á½ yá * w w w, û x 253, ( , , y l p j»(vector network analyzer; VNA gv ù (coplanar waveguide; CPW w œ d w» w ̃ ƒƒ 10, 20, 40 nm Ni 81 Fe 19 (Permalloy; Py w w d w.»q ql CPW x wš CPW Py /n S-q l d w.» 0Oe 490Oe¾ y j d w Py œ q 2.5 GHz 7 GHz ü ùkû»»ƒ f œ q ƒw y w. S-q l w ù œ q es w sy y ¼ p w Py 40 nm ¼ p (± wš w œ d ew. w Ì w ̃ S-q l»ƒ y w, œ Py ̃ 10 nm 40 nm¾ ƒw z sy yƒ 7.205(± koe 7.840(± koe ƒw y w. : œ, l p j», gv ù, ¼ p I. x, œw» e ful w w w š. š w ù v p w vp ƒ y š.»»» ƒ p w v w p v š w š w w w vp» w v w»» w w» š. v p» xw» w» w œ w» w y w w w wwš. v w d w ƒ w y w ƒ k w w. ù j» v w w. y w 10 4 ~10 7 v 10 psec~10 nsec ù. yx w inductive magneto-meter, SQUID, spin-polarized STM, magnetooptical effect, œ, v w d *Tel: ( , cyyou@inha.ac.kr w» œ d d ƒ d š š [1-3]. œ ƒ w w» j q» w w v j q ƒ ew j œ x w x. œ v n w œ w»» p sƒ w d 1946 J. H. E. Griffiths w Fe, Co, Ni w d š[4], 1947 W. A. Yager R. M. Bozorth w x y [5], C. Kittel w š w» [6]. œ x v w w sy y,» ¼ p w. w œ š q p sƒw wš y š [7].» FMR d š w š» y j š j q œ ü œ» d w. w CPW d w l p j» œ (vector network analyzer ferromagnetic resonance; VNA-FMR d» y k j ƒ š. p gv ù (coplanar waveguide; CPW p v f y GHz¾ Ÿ q p ƒ š» 18

2 Vector Network Analyzer w Py œ yáw Á½ yá 19 p sƒw» ww [8]. VNA-FMR d w Py Ì (10, 20, 40 nm w CPW ql m w w z, CPW w j q w /n d w [9]. l p j»(vector network analyzer; VNA d S-q l w œ q es w ¼ p w. w Ì w œ q w š Kittel œ w Py Ì z sy y w w. II. x x Si»q Py DC p rl ƒƒ 10, 20, 40 nm Ì w. w VNA-FMR d w» w 50 Ω p v CPW w corning eagle 2000 glass Ti(10 nm/cu(150 nm/ti(10 nm d rl ü œ ƒ torrw 9 Ar ƒ torr k w Cu Å/s, Ti Å/s ƒƒ 30 49, 2 59 w. œ Fig. 1(a, (b ƒ w Ÿ x w z Ar ƒ w w ql x w.»q CPW ƒ j» w Ti d 10 nm Ì w š Ti y d 10 nm Ì w. Fig. 1(a CPW ùkü l p j» v e w CPW p v 50 Ω w w. CPW p v (1 ùký. κ = a -- = b w/ = w/2 + s w w + 2s , κ' = ( 1 κ 2 (4 (2, (3, (4 ε r»q, t CPW Ì, w y s, s GSG(Ground-Signal-Ground s. w κ w s w. w CPW 50 Ω w» w»q (ε r = Ì(h =635µm, CPW GSG(Ground- Signal-Ground s(s =16µm y s (w = 100 µm VNA v 50 Ω e [10]. CPW Py š VNA-FMR d w Fig. 1(b» (H ext j q w» (H rf w k w v j q ƒ ew w ƒ ù» œ x ù. w œ x d w» w x yd g j q w» (H rf w ƒw ew. VNA-FMR d j q w /n d w 2- sp S-q l d w, w Fig. 1(c Z 0 = π K ( κ' ε K( κ eff (1 (1 ε eff r z Hilberg s equation w (2 [10]. ε eff = ( ε r + 1tanh 1.785log( h/s [ ] + ks/h [ ( ( k ] ( k ε r w, (1 (K(κ'/(K(κ CPW w. (2 K( κ = 1 0 dt ( 1 t 2 ( 1 κ 2 t 2 (3 Fig. 1. (a Schematic of CPW, (b Schematic of a sample on a CPW. Direction of the external magnetic field and RF field. (c The network analyzer 2-port probes are connected to the CPW.

3 20 CPW microwave GSG wafer probe(cascade Microtech Microprobes, 150 µm pitch and matched to 50 Ω w. VNA(8510C, Agilent 2-sp sp w GSG r v CPW g œ q d w. GSG r v d 45 MHz 40 GHz¾ VNA d q 45 MHz 50 GHz¾. gv(oscilloscope ƒ t wš, rp»ƒ q y s y w, VNA wù» q rp»ƒ q y w s ù S-q l d w. e p j» ¾ d ƒ w l p j» S-q l j», n, / v, w, d w. l p j» j q f w GPIB w WinCal-Xe (Cascade Microtech p j» v w. w w ISS(Impedance Standard Substrate; Cascade Microtech w Shortopen-Load-Thru(SOLT mw 45 MHz 15 GHz z d w š Thru (transmission, n y w CPW w. d w x yd g 0Oe 490 Oe¾ yw d w. III. x š VNA-FMR d mw Py œ q y w š w ¼ p wš Ì w. w z sy y w» w S- q l d w. S-q l ƒ sp /n w ùkü 2- sp S-q l q l S, S 22 n q l S 12, S 21 ùkü ƒƒ q l S = S 22 = 20log Γ (5 w»wz 20«1y, a, b ƒƒ y ùkü 1, 2 ƒƒ sp ùkü. S 12 =(b 1 / (a 2 (a 1 =0 w 2 sp yƒ n w z 1 sp w. S-q l (j» tx, db ù küš j» x. Fig. 2 Fig. 3 Py Ì S-q l ùküš, Fig. 2 S x ùküš Fig. 3 S ùküš. S» w z w» w (8 S» ƒw k S» 0 S S 12 = S 21 = 20log T (6. S 12 2 spƒ y š 1 spƒ y ùkü (5, (6 Γ T ƒƒ sp w n w []. S-q l w ùkü. b 1 b 2 = S S 12 a1 S 21 S 22 a 2 Fig. 2. FMR spectra of Im[ S ] (the imaginary part of S of Py (7 film at fixed fields ranging from 100 Oe to 490 Oe (a 40 nm, (b 20 nm, (c 10 nm.

4 연구논문 Vector Network Analyzer 를 이용한 Py 박막의 강자성공명연구 신용확 하승석 김덕호 유천열 값을 나타낸다. S = S(H 0 S(H = 0 (8 주파수 범위는 45 MHz에서 15 GHz까지 801개의 분해능으로 보정 작업 이후에 측정하였고 외부자기장에 의한 공명주파수 가 나타난 구간인 2.5 GHz에서 7 GHz까지 그래프 상에 나타 내었다. Py 박막의 길이와 폭을 10와 3 mm, 각각의 Py 박 막 두께는 Fig. 2와 Fig. 3에서 나타낸 바와 같이 (a는 40 nm, (b는 20 nm, (c는 10 nm로 측정하였다. Fig. 2와 같이 S 의 허수부에서 Py 박막 두께가 두꺼워 짐에 따라 각각의 외부 자기장에 대한 공명주파수가 미세하게 증가하는 21 것을 볼 수 있다[12]. 또한 Py 박막의 두께가 얇아질수록 S 의 허수부에서 상대적인 세기가 490 Oe의 경우 (40 nm, 0.036(20 nm, 0.020(10 nm로 작아짐을 볼 수 있 고 잡음신호가 좀 더 심해지는 것을 볼 수 있다. 그리고 외 부 자기장이 커질수록 공명 주파수의 제곱이 선형적으로 증 가하여 상대적으로 고주파로 이동하는 것을 볼 수 있다. 이 를 통해 Fig. 4(a에서는 170 Oe에서의 두께에 따른 공명주파 수의 증가를 나타내었고 y축(한 눈금 간격의 세기는 0.01의 상대적인 세기가 줄어드는 것을 볼 수 있다. Fig. 3과 같이 S 의 실수부에서는 신호의 세기가 양에서 음으로 바뀌는 부 분이 공명 주파수이며 신호의 위상 변화를 의미한다. Fig. 4(b는 S 허수부에서 peak 값과 실수부에서 위상 변화가 있는 부분의 상대적인 세기의 차이를 두께별로 함께 나타낸 것이다. 이 결과로 허수부의 peak 값과 실수부의 위상 변화 가 있는 부분이 일치함을 볼 수 있으며 또한 두께가 얇아질 (a Sample thickness dependence of the FMR signal intensity. Each spectrum was measured under an external magnetic field of 170 Oe. (b Re[ S] and Im[ S] of the measured S measured under an external magnetic field of 170 Oe for Py thickness = 40, 20, 10 nm. Fig. 4. FMR spectra of Re[ S] (the Real part of S of Py film at fixed fields ranging from 100 Oe to 490 Oe. (a 40 nm, (b 20 nm, (c 10 nm. Fig. 3.

5 22 w»wz 20«1y, » w y w. Py œ w tx [13]. w r = γµ 0 ( H eff + ( N y N z M s ( H eff + ( N x N z M s» w r, γ, H eff, M s ƒƒ œ q,» z, z» š sy y ùkü N x, N y, N z x j» w [13]. (9» w y w N x = N z =0 š N y =1 H eff» wš» w w w w r = γµ 0 ( H 0 + M eff H 0 ùký []. M eff z sy y ùkü. v w Landau-Lifshitz-Gilbert w ùký. dm = γm H eff + α dt M s (9 (10» γ, α, M s, H eff ƒƒ»z, ¼ p, sy y, š» ùkü. w v ùkü w š w w. (H 0 <<M eff Kittel œ w œ q (. 2 w r γ 2 2 µ H0 0 M eff dm dt M ( H 0 <M eff ( ( œ q H 0 w. Fig. 5 œ q x ƒw. w m z sy y ( w w Fig. 5 w. Fig. 5 v Ì z sy y ùkü Py ƒƒ 10 nm = 7.205(± koe, 20 nm = 7.705(± koe, 40 nm = 7.840(± koe y w. w ̃ f z sy yƒ f w. Fig. 2 x d e x Im[ S ] w = w r š s w dw. ¼ p, w =2αw M (12 ùký. (12 w M = γµ 0 M eff. ( (12 w ¼ p [14]. Fig. 5. The square of the measured resonance frequency as a function of applied field. The linear fit is based on Kittel s formula at small fields, w r 2 γ 2 µ0 2 H0 M eff. Inset: the effective saturation magnetization M eff obtained by fitting FMR data vs film thickness d Py. α w γµ 0 M eff (13 x d e S x mw ¼ p w, Py 40 nm (± Py ¼ p ew. IV. rl Py CPW VNA w œ x d wš w Py w w v w w. CPW 50 Ω p v e j» w š ƒ w Ti/Cu/Ti d. œ d CPW VNA mw œ d w. d œ l w Py œ q» w Ì œ q, w œ q w ¼ p z sy y Ì w š S-q l»ƒ Py Ì w w. Py Ì ƒ f œ q ƒ f S-q l» w ƒw. Py 40 nm, 20 nm, 10 nm 100 Oe 490 Oe¾ d w œ q 2.5 GHz 7 GHz¾ ùkû»» ƒ f œ q x ƒw

6 Vector Network Analyzer w Py œ yáw Á½ yá 23. š Py z sy y Ì w 10 nm = 7.205(± koe, 20 nm = 7.705(± koe, 40 nm = 7.840(± koe y w š ̃ f z sy yƒ f y w. w œ q s mw Py 40 nm ¼ p (± w. w w mw w» ù» l w ( š x [1] W. Dietrich, W. E. Proebster, and P. Wolf, IBM Journal, 189 (1960. [2] P. Wolf, J. Appl. Phys., 32, S95 (1961. [3] W. Dietrich and W. E. Proebster, J.Appl. Phys., 31, S281 (1960. [4] J. H. E. Griffiths, Nature, 158, 670 (1946. [5] W. A. Yager and R. M. Bozorth, Phys. Rev., 72, 80 (1947. [6] C. Kittel, Phys. Rev., 73, 155 (1948. [7] B. Heinrich and J. Bland, Ultrathin Magnetic Structure, Springer, Berlin (1994 pp. 195~222. [8] D. M. Pozar, Microwave Engineering, John Wiley & Son, New York (1998 pp. 160~167. [9] J. C. Sohn, M. Yamaguchi, S. H Lim, and S. H. Han, J. Magnetics., 10(4, 163 (2005. [10] T. C. Edwards and M. B. Steer, Foundations of interconnect and microstrip design, John Wiley & Son, New York (2000 pp. 161~224. [] S. Yoshida, H. Ono, S. Ohnuma, M. Yamaguchi, and Y. Shimada, Material Japan, 42, 193 (2003. [12] Y. C. Chen, D. S. Hung, Y. D. Yao, S. F. Lee, H. P. Ji, and C. Yu, J. Appl. Phys., 101, 09C104 (2007. [13] J. A. Osborn, Phys. Rev., 67(, 351 (1945. [14] G. Counil, J.-V. Kim, T. Devolder, C. Chappert, K. Shigeto, and Y. Otani, J. Appl. Phys., 95, 5646 (2004. Vector Network Analyzer Ferromagnetic Resonance Study of Py Thin Films Yong-Hwack Shin, Seung-Seok Ha, Duck-Ho Kim, and Chun-Yeol You Department of Physics, Inha University, Incheon , Korea (Received 19 November 2009, Received in final form 16 December 2009, Accepted 16 December 2009 Ferromagnetic resonance (FMR measurement is an important experimental technique for the study of magnetic dynamics. We designed and set up the vector network analyzer ferromagnetic resonance (VNA-FMR measurement system with home made coplanar waveguides (CPW. We examined 10-, 20-, 40-nm thick Py thin films to test the performance of the VNA-FMR measurement system. We measured S-parameter (transmission/reflection coefficient of Py thin films on a CPW. Resonance frequency is investigated from 2.5 to 7 GHz for a field range from 0 to 490 Oe. The VNA-FMR data shows the resonance frequency increment when the external magnetic field increases. We also investigated Gilbert damping constant of Py thin film using resonance frequency (w r and linewidth ( w. After investigating dependence of thickness, we find that an decrease in S-parameter intensity as Py thin film thickness decreases. And the FMR results show that the effective saturation magnetization, M eff, increase from 7.205(± koe to 7.840(± koe, while the film thickness varies from 10 to 40 nm. Keywords : ferromagnetic resonance, vector network analyzer, coplanar waveguide, gilbert damping constant