Short Notes IU89

phys. stat. sol. (a) z, IU89 (1983) Subject classification: 18.2.1 and 18.3; 22.8.2

Measurements of Magnetic Parameters of YBiFe Garnet Films

by Ferrimagnetic Resonance and Ferrimagnetic Antiresonance

BY J. BASZYhKI

Institute of Molecular Physics, Polish Academy of Sciences, Pomafi 1)

The ferromagnetic antiresonance effect (FMAR) has been observed for the first time on supermalloy by Yager /1/ and the transmission FMAR experiment was first carried out on a permalloy foil by Heinrich and Meshcheryakov /2/. Many other experimental and theoretical papers on the FMAR in metallic materials (with a large electrical conductivity) were published in recent years. The first time FMAR in non-conducting materials has been observed on YIG films by Dewar et al. /3/. Chan and Fraitova /4/ suggested the macroscopic theory of the FMAR in weakly electrically conducting ferrimagnetic materials.

The measurement of both FMR and FMAR is a new method of determing the magnetization 4fM of "as-grown" non-conducting ferrimagnetic films /3/. The perpendicular anisotropy, characteristic of bubble materials, does not com- plicate the determination of the magnetization.

The description of a ferrimagnet response to an externally applied static field H and a small radio frequency electromagnetic field has been given else- where /5/.

The resonance conditions of the FMR and FMAR for H applied perpendicular to the film plane are /3/

w / r = HFMR - 4XM + HU ,

and for H applied in the film plane a re /6/

1 ) Smoluchowskiego 17/19, 60-1 79 Poznah, Poland.

a90 physica status solidi (a) 76

Fig. 1. First derivative dP/dH of.the microwave power transmitted through a YBiFe coated GGG substrate versus magnetic field H, a) parallel (HFMR =

= 6. O W 0 A/m, HFMm = 5 . 8 6 ~

A0 A/m) and b ) rpendicular (HFMR = 4.02x1 $eA/m, HFMm =

= 3 . 7 8 ~ 1 0 A/m) to the sample. The microwave frequency w a s 18.75 GHz. The FMR and FMAR peaks are labelled

5

5

5

when the magnetocrystalline anisotropy is negligible. In (1) to (4) w is the

angular frequency of the rf radiation, 7 is the gyromagnetic ratio, M is the magnetization, H is the uniaxial anisotropy perpendicular to the sample plane,

U is the magnetic resonance field. and H ~ ~ ~ , H~~~

From (1) and (2) w e see that

4xM = HFMR - H~~~ * (5)

FMR and FMAR measurements were made on YBiFe garnet film grown on the

GCG substrate by the LPE method. In the demagnetized state a typical stripe structure at 1 . 7 pm period was observed.

. At the microwave frequency, 18.75 GHz, magnetic properties of (111)

oriented YBiFe garnet film, 10 pm thick, have been investigated using the

microwave transmission technique /3/. The YBiFe coated wafer was mounted over the open end of a waveguide with a holding plate. A second waveguide,

axially rotated about 8 7’ to the first, wasattached to the other sideof the holding plate. The two waveguides functioned a s two crossed polarizers with YBiFe between them. A static magnetic field H w a s maintained normal o r parallel to

the plane of the sample. This transmission was monitored by a diode detector. The FMR and FMAR spectra were detected a s the first derivative of the trans-

mission signal using a 400 Hz modulation magnetic field. All FMR and FMAR measurements were made at room temperature.

Typical spectra a r e shown i n Fig. l a and b. The magnetic parameters characterizing the YBiFe garnet film were

determined from the above data of FMR and FMAR effects by our fitting pro-

cedure. These parameters a r e

Short Notes KL 91

4aMeff = 4?sM - HU = (-0.163)mT - F M R ,

4 r M = (0.030)mT - FMR and FMAR , HU = 1 . 5 3 6 ~ 1 O5 Am” - FMR and FMAR , g-factor = 2.007 - FMR and FMAR, and Q = KU/2aMs = 6.6. 2

The author would like t o thank Dr. A. Dz&kowski of the Institute of Physics,

Polish Academy of Sciences, for making this mater ia l available t o us. This work was supported by the Inst i tute of Physics, Polish Academy of

Sciences.

References /1/ W.A. YAGER, Phys. Rev. - 73, 1247 (1948).

/2/ B. HEINFUCH and V. A. MESHCHERYAKOV, Zh. eksper. teor. Fiz. g,

/ 3 / G . DEWAR, V.R.K. MURTHY, M. SHONE, and R. BELT, J. appl. Phys. 424 (1970).

- 53, 2101 (1982).

/4/ N. CHAN and D. FRAITOVA, Czech. J. Phys. - B32, 1288 (1982).

/5/ A.G. GUREVICH, F e r r i t e s at Microwave Frequencies, Fizmatgiz, Moscow 1960 (in Russian).

/6/ J.F. COCHRAN, K. MYRTLE, and B. HEINRICH, J. appl. Phys. - 53, 2261

(1 98;).

(Received February 7, 1983)