COMPARISON OF THE SHORT-RANGE ORDER OF AMORPHOUS AND CRYSTALLINE (Fe,Ni)B ALLYOS

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COMPARISON OF THE SHORT-RANGE ORDER OF AMORPHOUS AND CRYSTALLINE (Fe,Ni)B

ALLYOS

J. Balogh, Gy. Faigel, M. Tegze, T. Kemèny, A. Schaafsma, I. Vincze, F. van der Woude

To cite this version:

J. Balogh, Gy. Faigel, M. Tegze, T. Kemèny, A. Schaafsma, et al.. COMPARISON OF THE SHORT- RANGE ORDER OF AMORPHOUS AND CRYSTALLINE (Fe,Ni)B ALLYOS. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-255-C1-256. �10.1051/jphyscol:1980186�. �jpa-00219779�

JOURNAL DE PHYSIQUE Colloque Cl

,

COMPARISON OF M E SHORT-RANGE ORDER OF AMORPHOUS AND CRYSTALLINE ( ~ e r ~ i ) ~ ALLOYS

+ +

J. Balogh, Gy. Faigel, M. Tegze, T. Kemsny, A.S. Schaafsma, 1.Vincz.e and F . Van der Woude

+

Central Research I n s t i t a t e for Physics, Budapest, Hungary.

Solid State Physics Laboratory, MateriaZs Science Center, University of Groningm, Groningen, The .NetherZds.

From a fundamental as well as a technological point of view the metallic glasses show attractive properties which are due to the amorphous structure.

Physical properties which are sensitive for local configurations can provide valuable information on the nature of the short-range atomic arrangements.

The chemical short-range order of ferromagnetic me- tallic glasses is reflected in the hyperfine field distribution p(H) because of its sensitivity for the local environments. In a series of transition metal- -metalloid systems with one magnetic constituent it was found /1/ that the average hyperfine field is proportional to the average magnetic moment of the magnetic component. It is well-known from compari- sons between various intermetallic compounds that the magnetic moment is determined mainly by the num- ber of nearest metalloid neighbours, that is the magnetic mment (or hyperf ine field) distribution reflects mainly the distribution of the neighbouring metalloid atoms.

It has been shown /2/ that in the crystalliza- tion of Fel-xBx (0.15 5 x 5 0.25) glasses the FeT5BZ5 composition plays a prominent role. During the crystallizat'ion of these glasses two processes were observed, namely: 1, a precipitation of a-Fe until the composition of the remaining glass reaches the FeT5BZ5 composition and 2, the glass with this composition transforms into the metastable Fe3B in- termetallic compound. The iron p (H) distribution measured by MiSssbauer method in the am~rphous FeT5BZ5 alloy could be satisfactorily described /3/

with the assumption that its local environments are similar to those in the Fe3B compound.

These results suggested a more general model according to which /3/ the complex structure of me- tallic glasses at arbitrary composition is determi-

+On leave from the Central Research Institute for Physics, Budapest, Hungary.

ned by two d&ant contributions, namely i, structural disorder, and

ii

,

In this tenruinology structural disorder means the lo- cal distort ion of the corresponding intermetallic compound (in the above case: 'IM75M25) which can be characterized by a Gaussian broadening of the lat- tice parameter and consequently also of the hper- fine field around the crystalline values. Chemical disorder results from deviations from this special composition which cause distortion of the "ideal"

amorphous structure (that of the 'M75M25 glass) and can be described in analogy to the case of non-stoi- chiometric intermetallic compounds.

In this paper we report the prelim* results of the first systematic investigation of the effect of structural disorder in metallic glasses. The amorphous (Fe, -gix) 75B25 alloys are especially sui- table for this study because they crystallize into a single phase. The X-ray controlled amorphous sam- ples were prepared at the Central Research Institute for Physics, Budapest by quenching onto the external

surface of a rotating copper disk. The X6ssbauer measurements were evaluated with the method of Ref.

4. According to X-ray evidences the samples between

x = 0 and 0.5 crystallize into the metastable tetra- gmal Fe3B structure isostructural to Fe3P. The structure has three crystallographically inequivalent iron sites with ZB, 3B and 4B nearest neighbours.

Fig. 1 shows the concentration dependence of the average hyperfine field for the amorphous and crystalline alloys. It is important to note that decreases between x = 0 and 0.5 about 10% but the %e amorphous and crystalline values agree with each other within 1-290. This suggests strong similarities in the short-range order of these glasses and meta- stable crystalline compounds.

Fig. 2. shows the temperature dependence of the

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980186

C1-256 JOURNAL DE PHYSIQUE

Fig. 1. Average iron hyperfine f i e l d extrapolated t o 0 K i n amorphous and crystalline (Fel-xNix) 75B25 al- loys.

I ^'"-

- g

-

I?

II 220

average hyperfine f i e l d s of the amorphous and crys- t a l l i n e (FeO. 5Ni0. 5) 75B25. The difference between the magnetization curves of the amorphous and crys-

- b

amorphous

o crystalline

a

-

I I I I I

t a l l i n e s t a t e s is smaller than 5% and the magnetiza-

0 0.1 0.2 0.3 0.L 0.5

tion i n both s t a t e s decreases much f a s t e r with tem- perature than in metallic iron. This shows that the structural disorder has a minor effect on the shape of the magnetization curve and that the high metal- loid content i s responsible for the rather f a s t de- crease of magnetization i n these materials. This con- clusion contradicts a view which can be found i n the l i t e r a t u r e /5/ and was obtained from an incorrect comparison of the magnetization curves of metallic iron and metallic glasses.

Fig. 3 shows significant differences between the P ( ~ ) of Fe75B25 and (Fe0.5Ni0.5)75B25' I t is very remarkable that the calculated curve i n Fig. 3b

(with no adjusted parameter) reproduces reasonably well the narrowing of p(H) (In t h i s calculation the

crystalline hyperfine f i e l d values were experimen-

0 2 1 amorphous lTc=630t2KI

I

I

I b

^_

TITc

-

Fig. 2. Temperature dependence of the reduced ave- rage iron hyperfine f i e l d i n amorphous and crystal- l i n e (Fee. 5Ni0.5)75B25~

0 ^{I I I}

I

0 100 200 300 LOO

HtkOe)

-

Fig. 3. Measured (broken line) and calculated ( f u l l line) iron hyperfine f i e l d distributions. The dotted lines show the broadened distributions around the crystalline hyperfine f i e l d s (represented by the bars) corresponding to 2B, 3B and 4B nearest neigh- bours. a, Fe75BZ5 ( a t 80 K, reproduced from Ref. 3) : the only parameter used i n the f i t was the relative broadening of the crystalline hyperfine f i e l d s , AH/H

= 0.103. b, (Feo. 5Nio. 5) 75B25 (extrapolated t o 0 K) : there i s no free parameter i n the calculated curve

(AH/H = 0.103 as deduced from Fe75B25).

t a l l y determined from the cr. (Fe0.5Ni0.5)75B25 com- pound). This again strongly supports the assumption that in the investigated cases the short-range order of the glass and crystalline compound is nearly iden- t i c a l .

Acknowledgements. - We are grateful t o A. Lovas and J. Takiics f o r preparing the samples, t o Mrs. K.

Zhb6 for the chemical analysis and t o F. van der Horst f o r the X-ray measurements. This work forms part of the research program of the Foundation for

Fundamental Research on Matter (FCM)

,

References

/1/ Heidemann, A., Z. Phys.

B20

6 (1976) 1185; Tsuei, C.C., Longworth, G. and -. Lm, S.C.H., Phys. Rev.

170

/2/ KemSny, T., Vincze, I . , Fogarassy, B. and Arajs, S.

,

/3/ Vincze, I . , Kemzny, T. and Arajs, S., Phys. Rev.

B, to be published.

/4/ vincze, I . , Solid State Conmum. 25 (1978) 689.

/ 5/ Graham, C. D. and Egami

,

,

.

Sci.,

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