MAGNETOMECHANICAL COUPLING IN THE Fe85B15 AMORPHOUS ALLOY RIBBONS PRODUCED IN LONGITUDINAL AND TRANSVERSE FIELD DURING QUENCHING

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MAGNETOMECHANICAL COUPLING IN THE

Fe85B15 AMORPHOUS ALLOY RIBBONS

PRODUCED IN LONGITUDINAL AND

TRANSVERSE FIELD DURING QUENCHING

Z. Kaczkowski, É. Kisdi-Koszó, L. Potocký

To cite this version:

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JOURNAL DE PHYSIQUE

Colloque C8, Suppl6ment au no 12, Tome 49, d6cembre 1988

MAGNETOMECHANICAL COUPLING IN THE

FeggB15

AMORPHOUS ALLOY

RIBBONS PRODUCED IN LONGITUDINAL AND TRANSVERSE FIELD DURING

QUENCHING

Z. Kaczkowski (I), E. Kisdi-Kosz6 (2) and L. Potockf (3)

( I ) Polish Academy of Sciences Institute of Physics, AI. Lotnikdw 32/46, PCO2-668 Warszawa, Poland

(2) Hungarian Academy of Sciences Central Research Institute for Physics, H-1525, Budapest P O B 49, Hungary (3) Faculty of Science, P. J. Safarik University, N a n . Februarov6ho Vitazstva 9, 04154 Kogice, Czechoslovakia

Abstract. - The magnetomechanical coupling coefficient of the measured 50 mm long and 4 mm wide strips of the as-quenched FessB15 amorphous alloy reaches its maximum values between 0.18 and 0.25. After applying longitudinal or transverse magnetic field (H = 8 kA/m) during quenching process the maximum values of this coefficient increases to 0.4 f 5 %.

1. Introduction

Saturation magnetostriction is one of the important magnetic properties characterizing the magnetic metallic glasses. Magnetostriction has influence on magnetic properties and determines the piezomagnetic and mechanical properties because it is closely re- lated to the structure and magnetic and mechanical anisotropies. The saturation magnetostriction constant of the Fe-B amorphous alloys containing 15 at %

of the boron has values changing from 21 x to 32

x

depending mainly on the melt technique [I, 21. The properties of the piezomagnetic materials

- which belong generally t o the soft magnetic materials with high magnetostriction (usually higher than 15 x lo-*) are characterized by the piezomagnetic co- efficients occuring in piezomagnetic equations and by one of the most important parameters: the magnetomechanical coupling coefficient, e.g. [3]. The square of the magnetomechanical coupling coefficient defines which part of the magnetic (or mechanical) energy is converted into mechanical (or magnetic) energy.

about 34 pm. After applying in-plane the same value of the transverse field during quenching the thickness

t was equal to 25 pm. For the ribbons produced without magnetic field the thickness was equal to 30 p m . From these ribbons the 50 mm long and 4 mm wide strips were cut. Mass of the investigated samples was equal to 48.95 mg for longitudinal field, 36.55 mg for the transverse field and 44 mg for strip cut from the ribbons produced without magnetic field.

The magnetomechanical coupling coefficient k was calculated from the relative differences betwen moduli of elasticity

EB

a t constant magnetic induction and

EH

at constant magnetic field, e.g. [3, 61, i.e.

These moduli were calculated from resonant and antiresonant frequencies obtained from motional impedance circles, e.g. [6]. The dependences of the moduli of the elasticity on the magnetic bias field are in figure 1. The amplitude of the AC magnetic field was equal to 3 A/m and resonant frequencies were changing from 40 to 46 kHz. The dependences of the

2. Experimental results

The soft magnetic properties of the amorphous alloys can be improved by field annealing after quenching. This annealing very often may be the reason for the high ribbon brittleness. In order to avoid this problem a new quenching procedure has been intro- duced. During the quenching the magnetic field was applied [4, 51. The about 8-10 rnm wide FessBls amorphous ribbons were produced with applied parallel and in-plane transverse magnetic field with respect to the ribbon axis during quenching. Wheel speed was kept constant. The thickness of the produced ribbons dif-

fers depending on the direction and the strength of o L O O 800 H [ A I ~ the applied field. After applying longitudinal field dur-

ing quenching H = 8 kA/m) the ribbon thickness was Fig. 1.

-

Moduli of elasticity vs. magnetic bias field.

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C8

-

1352 JOURNAL DE PHYSIQUE

coupling coefficient k on the bias field are given in fig- ure 2. The magnetomechanical quality factor Q was calculated from the resonance frequency

f,

and the quadrantal frequencies f* and

f2

161, i.e.

The dependences of Q versus H a r e presented in fig- ure 3.

plying a transverse field, which increases the number of the in-wlane transverse domains. Maximum values of the magnetomechanical coupling coefficient (Ic, = 0.40 f 5 %) are nearly two times higher than those for as-quenched ribbons produced without magnetic field (Ic, = 0.18 - 0.25). The quality factor Q reaches 1200 for the transverse field, 1100 for the longitudinal field and 900 for H = 0. Minima of the Q (from 50 to 200) are observed a t bias fields where maxima of H and minima of EH occur. This; is connected with the domain structure in the as-quenched state and its changes during the magnetization process, espec idly with non-180' Bloch wall movements and magnetization vector rotations. This last phenomenon has the greatest influence on the piezomapetic properiiies of the samples produced in the magnetic fields. The obtained results are similar t o those fbr the-iron rich Fe- Si-B metallic glasses annealed in -the longitudinal or

Fig. 2.

-

Magnetomechanical coupling coefficient vs. bias field.

Fig. 3. - Magnetomechanical quality factor vs. bias field.

3. Discussion and conclusions

Quenching in parallel magnetic field increases the number of the strip domains parallel to the ribbon axis. This partially ordering improves the piezomagnetic properties. Similar situation occurs after a p

transverse magnetic fields, e.g. [7] but the samples are not brittle.

The magnetomechanical coupling; vanishes in the de- magnetization state ( E H ~ = EBo) and at the magnetic saturation. In this last case EHs = EBs = E where E is the real elasticity modulus (proportionality coefficient between the stresses and strains). When the magnetic domain structure vanishes the Hoolces law is valid and E is the material constant.

[I] Potocky, L., Mljmek, R., Kisdi-Kod, E., T d c s , J., Sarmely, P., Proc. Int. Conf. on Metallic Glasses (Budapest) 1980, pp. :101-105.

[2] O'Handley, R. C., Narasimhan, M. C . , Sullivan, M. O., J. Appl. Phys. 50 (1979) 1633-1635. [3] Kaczkowski, Z., Arch. Acoust. 6 (1981) 385-400. [4] Yu, M. Y., Huang, D. K., Yas. P. C., Hou, S. E.,

Muter. Res. Soc. Proc. 58 (1986) 19-22. [5] Poghy, L., Kiss, L. F., Lovac::, A., Kisdi-Kosz6,

E., Konczos, G., Symp. on Magnetic Properties of Amorphous Metals (Benalmadena) 1987, p. 87. [6] Kaczkowski, Z., Magnetic Properties of Amor- phous Metals, Eds. A. Hernando, V. Madurga, M. C. Sanches-Tkujillo, M. Vazquez (Elsevier Sci. Publ. B.V., Amsterdam) 1987, pp. 136-138. [7] Brouha, M., van der Brost, J., J. Appl. Phys. 50