ANISOTROPIC FLOW OF PRECESSING MAGNETIZATION ENERGY ALONG THE SURFACE OF METAL-METALLOID FOILS AT X-BAND FMR

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ANISOTROPIC FLOW OF PRECESSING

MAGNETIZATION ENERGY ALONG THE

SURFACE OF METAL-METALLOID FOILS AT

X-BAND FMR

K. Kakuno, T. Namegaya

To cite this version:

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JOURNAL DE PHYSIQUE

Colloque C8, Supplement au no 12, Tome 49, decembre 1988

ANISOTROPIC FLOW OF PRECESSING MAGNETIZATION ENERGY ALONG

THE SURFACE OF METAL-METALLOID FOILS AT X-BAND FMR

K. Kakuno and T. Namegaya

Department of Electrical Engineering, Faculty of Engineering, Yokohama National University, Hodogaya-Ku Yokohama 240, Japan

Abstract. - Resonant transmissions of microwave radiations are studied with a double cavity FMR spectrometer. The

anisotropic resonant transmissions are observed. The energy flow propagating across the grooves formed on the sample surface is found to be mainly responsible for the observed anisotropic resonant transmissions.

I n t r o d u c t i o n

Unexpectedly strong resonant transmissions of microwave radiations from the one cavity to the other have been observed with a double cavity FMR spectrometer having two identical microwave cavities between which a sample foil is tightly clamped so as t o form the common wall a t the coupling hole bored in the bottom of the each cavity [I]. We have reported that these unexpected resonant transmissions of microwave radiations result from the energy flow prop* gating along the sample surface in the form of something like a magnetoelastic wave generated by a precessing magnetization on a part of the surface [2]. It has been also found that they strongly depend on the angle between the direction of the in-plane static magnetic field and that of the fine grooves running on the sample surface [3]. The existence of the grooves is a feature of rapid quenched metal-metalloid ribbons produced in the roll method. In the present work, it is shown experimentally and discussed how these grooves have to do with the anisotropic energy flow responsible for the observed resonant transmissions of microwave radiations.

E x p e r i m e n t s

The experimental arrangement is a double cavity

FMR spectrometer described above in detail. The static magnetic field HO is applied parallel t o the sur-. face plane of the sample, where 0 is the angle between the static magnetic field and the microwave magnetic field. The microwave power transmitted from the one cavity to the other is measured as a function of Hs

with the angle

6

as a parameter. This microwave power shows a clear resonant peak at the static magnetic field corresponding t o the FMR, as reported in the previous paper [I]. The peak values of the transmitted microwave power plotted as a function of the angle 0 reveal anisotropic behaviors of the resonant transmissions. The sample foils are prepared in such a manner that the original long ribbon is cut off in the same length as its width into square samples. The dotted lines AB and CD in figure 1 denote the cut-

U ~ uoff tLine

Fig. 1. - Illustration of the sample preparation.

ting lines. The each sample has a lot of fine grooves parallel t o the edges AC and BD on its surface plane. The samples studied here are square foils cut off from a rapid quenched Fe7sSiloBlz ribbon of 30 pm thick- ness. These samples are called "as-prepared" samples. In order to clarify how the pitch of the grooves and their direction have to do with the anisotropic behaviors of the present resonant transmissions, we prepare another group of samples artificially grooved on their surface by etching, having various pitches in the direction parallel or perpendicular t o the original grooves. These samples are called "artificially grooved" samples of the parallel type or the perpendicular type, respec- tively. The sample angle is defined as a, when the square sample is clamped in such a manner that the direction of the original grooves makes an angle a with the microwave magnetic field.

E x p e r i m e n t a l r e s u l t s and discussion

Figure 2 shows the resonant transmission peak values plotted as a function of the angle 6 with the sample angle a as a parameter, where an as-prepared sample is used. It is clearly observed in this figure that the observed resonant transmission peak strongly depends on both the static magnetic field direction and the sample angle. The one of these curves for a = O0 takes the maxima at 0 = 0". and 6 = 180'. This feature of the curve is typical of the case a = 0'. The other for

a = 90' has the maximum at 0 = 90'. This feature is typical of the case a = 90°. Figure 3 shows the res- onant transmission peak values plotted as a function of the angle 0 for a =

o',

where the samples used are an as-prepared one and three artificially grooved ones

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C8 - 2018 JOURNAL DE PHYSIQUE " 20 Sample Angle 90' a W a --t As- prepared Z 0

W

I0

2 ,-

LL 0 Z != Y, 0 Z ₀ ₃₀ ₆₀ ₉₀ ₁₂₀ _IY) ₁₈₀

,-

5 8 [degJ

Fig. 4. - Resonant transmission peak values plotted as a

~ i2. ~- ~esonant . transmission peak values plotted as a _function

of the angle 0 for LY = 90'. An *prepared sample

of the

'.

a = O0 and = An as- and three artificially grooved ones of the perpendicular type prepared sample is used. _{are used.}

Fig. 3. - Resonant transmission peak values plotted as a function of the angle 0 for CY = 0'. An as-prepared sample

and three artificially grooved ones of the parallel type are used.

of the parallel type with the pitches of 60 pm, 21 pm and 15 pm. As seen in this figure, the three artificially grooved samples of the parallel type show the essentially same feature as the as-prepared one, typical of the case a = 0". Figure 4 shows the resonant transmission peak values plotted as a function of the angle 19 for

a

= 90°, where the samples used are an as- prepared one and three artificially grooved ones of the perpendicular type with the pitches of 60 pm, 21 pm and 15 pm, having the artificial grooves perpendicular t o the original ones. As seen in this figure, the as-prepared sample shows the typical feature of the case a = 90°, but the artificially grooved ones with the pitches of 21 pm and 15 pm show the typical feature of the case a = 0" rather than the case

a

= 90": For the artificially grooved sample with the pitch of 60 pm, the sign appears that the feature of the case

a = 90' begins t o be lost and to change into that of the case a = 0'. These experimental results show that the artificial grooves change the preferential direction of the anisotropic energy flow responsible for the observed resonant transmissions and that the ex- tent of this effect depends on the pitch of the artificial grooves. It should be noted in these figures that the intensity of the rsonant transmission peak becomes strongest when the static magnetic field is applied parallel to the artificial grooves as well as the original ones formed naturally. As it has been confirmed by the pre- vious experiments [3] that the energy flow takes place in the direction perpendicular t o the static magnetic field, the above experimental results also show that the energy flow propagating across the grooves is responsible for the observed resonant transmissions and that the anisotropic behaviors of the resonant transmissions are mainly due to the grooves.

It is also suggested that the grooves serve as a kind of gratings for the energy carrier something like magnetoelastic waves.

Conclusion

The energy flow propagating across the grooves formed on the sample surface is considered as mainly responsible for the observed anisotropic resonant transmissions.

[l] Kakuno,

K.,

Kubota, T. and Yamada, T., J p n . J.

Appl. Phys. 24 (1985) L481.

[2] Kakuno, K., Oshima, Y., Kondo, K. and Shido, M., Proc. Intl. Phys. hlagn. Mat. Sendai (1987) 532.