Elasticity moduli dependences on magnetic field for Fe80.2Cr2Si3.8B14 metallic glass

Journal of Magnetism and Magnetic Materials 101 (1991) 23-24 North-Holland

Elasticity moduli dependences on magnetic field for Fe,&r, Si 3.8B,, metallic glass Z. Kaczkowski a and P. Duhaj b ‘PolishAcademy of Sciences Institute of Physics,

Al. Lotnik6w 32/46, PL-02-668 Warsaw, Poland ’ Slovak Academy of Sciences Institute of Physics EPRC, Dubravska cesta 9, CS-84228 Bratislava, Czechoslovakia

AE effect in Fe,,,2Cr,Si~~sB,, strip-shape samples was determined for the as-quenched state and after the annealing. The moduli of elasticity were changed from 83 to about 170 GPa and their minima occurred at the bias field equal to 140-300 A/m before heat treatment and at 80-120 A/m after annealing at 35O’C for 1 h.

1. Introduction Magnetostriction and anisotropy determine the piezomagnetic properties of the magnetic materials, among them the AE effect. They have a great influence on the magnetic, mechanical and magnetomechanical properties of materials because they are closely connected with their structure. The elastic manifestation of the magnetoelastic coupling effect results from the interaction of magnetostrictively deformed domains with the external stress field. The AE effect is defined as the relative change of the elasticity modulus [(Es - E,)/E,] when the magnetic field (H) is increasing from the demagnetization state (E,) to the magnetic saturation (Es). The iron-rich metallic glasses have a high magnetostriction and good piezomagnetic properties, see e.g. refs. [l-5]. Chromium was added to these alloys to improve the corrosion resistance.

minimum of the impedance modulus (Z,,)] of the investigated strips (which were the half-wave resonators, I = X/2, i.e. EH = 412fr2p,

EB = 4I=fzp,

Oh(2)

were determined versus the magnetic bias field (H). The characteristics for the as-quenched and for the annealed samples at a temperature of 350” C for 1 h samples are presented in fig. 1. The dependences of the maximum and minimum values of the impedance moduli Z on the magnetic bias field are given in figs. 2 and 3 and AE/E, in fig. 4. 3. Discussion and conclusion The curves of EH and EB for the as-quenched state exhibit the minima at the bias fields equal to 140 and 300 A/m and 80-120 A/m for samples nos. 1 and 2, respectively, and after annealing at 350 ’ C these minima occur at H = 80 and 120 A/m, respectively. The moduli

2. Experimental The metallic glass ribbons were prepared by the melt-spinning technique. Their width was equal to 30 mm and thickness was changing from 22 to 25 pm. Their composition was as follows: Fes,,,CrzSi,,,B,,. The strip-shape samples with the length equal to 50 mm and width of 4 mm were cut from one ribbon and measured using the resonance-antiresonance method. The amplitude of the ac magnetic field was between 2 and 3 A/m. Their density (p) was equal to 7.36 Mg/m3 and their saturation magnetostriction (A,) was reaching the value of 30.6 X 10W6. The characteristics of the moduli of elasticity at constant magnetic field ( EH) and at constant magnetic induction ( EB), calculated from the frequencies of the resonance [( fr), i.e. the frequency for the maximum of the modulus of impedance (Z,,)] or of the antiresonance [(f,), i.e. the frequency for the

I

I

I

I

I

0

0

200

400

600

800

I

1

as cast

1000 H [A/m 1

Fig. 1. Elasticity moduli at constant magnetic field (EH) and at constant magnetic induction ( EB) vs. magnetic bias field H for two samples before and after annealing at 350 o C for 1 h.

0312-8853/91/%03.50 0 1991 - Elsevier Science Publishers B.V All rights reserved

Z. Kacrkowski,

24

t

&I

P. Duhaj / Elasticity

P

,,4

1

J I I. 1 -1600 -1200 - 800 -400

0

I

1

400

800

I I _ 1200 HIAIm

Fig. 2. Initial curve ( + ) and hysteresis loop ( + , * ) of the maximum (Z,,,) and minimum (Z,,,) values of the impedance moduli for the half-wave length resonator (no. 1) before annealing.

OL

7r12

0’

I

I 200 1

I

200

400 _

I 600

I

I

I 400

I 600

I 800

I 1000 H

I

I

I

I 1000 H

800

I I LA/m 1 I I

I [A/ml

Fig. 3. Maximum (Z,,,) and minimum (Z,,,) values of the impedance moduli for half-wave length resonators (nos. 1 and 2) vs. magnetic bias field H before and after annealing at 350°C for 1 h.

E.-Et

I

I

I

I

I

were

treatment

350”Clh

Fig. 4. Effect AE in two samples before and after annealing 350’Cforl h.

and

changing from

References

I

[l] P.M. Anderson

x t

a B,4 glass

from 130 to 160 GPa before 83 to 171 GPa after annealing. The magnetization vector rotations occur near the knee of the magnetization curve. The minima of moduli of the elasticity were observed in this region and the maximum of the magnetomechanical coupling was at the same or something lower magnetic bias field. When the magnetomechanical coupling vanishes, i.e. at the demagnetization state and at the magnetic saturation (when the domain structure vanishes and all the magnetization vectors are parallel to the direction of the magnetic bias field H) the moduli of elasticity at constant magnetic field ( EH) are equal to the moduli of elasticity at constant magnetic induction (Es), i.e. EHo = Es0 and E,, = E,,. The dynamics of the half-wave length resonators is connected with the diameter of the motional impedance circles, i.e. with differences between impedances at resonance (Z,,,) and at antiresonance ( Zmin). The changes of the impedances with magnetic bias field are similar to the changes of the moduli of elasticity, i.e. AE effect (fig. 4) and to the changes of the magnetomechanical coupling coefficient k. The hysteresis loops of the impedance (fig. 2) exhibit symmetry and they are in evidence that these metallic glasses are soft magnetic materials with very narrow hysteresis loop. The A E effect after annealing increased more then three times, i.e. for sample no. 1 (E, E,)/E, = 0.094 for as-quenched state and 0.35 after annealing and for sample no. 2 0.051 and 0.30, respectively. More important for technical applications is the relative difference between maximum and minimum values of the elasticity moduli. For sample no. 1 (E, EHmin)/Es = 0.17 before and 0.51 after annealing and for sample no. 2 0.12 and 0.52, respectively. The magnetomechanical coupling coefficient k which is responsible for the A E effect reaches a maximum for sample no. 1 at 140 A/m for the as-quenched state (k, = 0.22) and at 80 A/m after annealing at 350° C (k, = 0.52) and for sample no. 2 at 240 A/m (k, = 0.17) and at 100 A/m (k, = 0.53), respectively. This alloy is a good material for the ultrasonic transducer cores or for the magnetostrictive delay lines. heat

Z mm x

200

of Fe,,firJSi,

of elasticity

A

as cast

moduli

at

III, J. Appl. Phys. 53 (1982) 8101. [2] Z. Kaczkowski and P. Duhaj, Acta Phys. Pol. A 76 (1989) 183. [3] M.A. Mitchell, A.E. Clark, H.T. Savage and R.J. Abbundi, IEEE Trans. Magn. MAG-14 (1978) 1169. [4] M.A. Mitchell, J.R. Cullen, R. Abbundi, A.E. Clark and H. Savage, J. Appl. Phys. 50 (1979) 1627. [5] C. Modzelewski, H.T. Savage, L.T. Kabacoff and A.E. Clark, IEEE Trans. Magn. MAG-17 (1981) 2837.