THE HYPERFINE INTERACTIONS IN THE INVAR ALLOYS ON Fe-Pt BASE

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THE HYPERFINE INTERACTIONS IN THE INVAR ALLOYS ON Fe-Pt BASE

P. Stetsenko, S. Antipov, V. Satbajev

To cite this version:

P. Stetsenko, S. Antipov, V. Satbajev. THE HYPERFINE INTERACTIONS IN THE INVAR ALLOYS ON Fe-Pt BASE. Journal de Physique Colloques, 1971, 32 (C1), pp.C1-1117-C1-1118.

�10.1051/jphyscol:19711398�. �jpa-00214438�

JOURNAL DE PHYSIQUE

Colloque C I , supple'ment au no 2-3, Tome 32, Fe'vrier-Mars 1971, page C 1 - ^{11 17}

THE HYPERFINE INTERACTIONS IN THE INVAR ALLOYS ON Fe-Pt BASE

P. STETSENKO, S. ANTIPOV, V. SATBAJEV State University, Moscow, U. S. S. R.

Rburnk. - Nous avons effectui des mesures d'effet Mossbauer sur le Fe57 dans les alliages ternaires Fe70[Ptl-,(Rh, R e ) z ] l ~ oh x varie de 0 A LO %. Les spectres Mossbauer obtenus montrent une separation des raies correspondant a I'existence de deux valeurs de champ effectif sur le Fe57, qui peuvent &tre dues A la coexistence de phases ferro- et antiferromagnetiques dans les alliages. Ceci est aussi confume par les mesures de dependance en tem*rature de l'intensite des raies de resonance des photons

pour une source et ^un absorbeur immobiles.

Abstract. - The measurements of Mossbauer effect on Fe57 were performed in the ternary alloys Fe70[Ptl-,(Rh, Re)z]3~, where x varies from 0 to 10 %. ?he Mossbauer spectra obtained show the splitting of lines, corresponding to the existence of two values of effective fields on Fe57, which may be due to the coexistence of ferro- and antiferromagnetic phases in alloys. This is also confirmed by the measurements of temperature dependence of the inten- sity of resonance line of y-photons by the motionless source and adsorber.

The specific properties of invar alloys attract the attention already for a long time, but physical nature of these properties remained unclear. The essential contribution to the interpretation of iron-nickel invar alloys properties was made by investigations of Kondorsky and Sedov [I] where some peculiarities of these alloys were explained by the assumption of cc latent antiferromagnetism

in y-iron.

In several works of Nakamura [2] this hypothesis was confirmed by the Mossbauer effect measurements in some invar alloys. In these investigations it was shown that Mossbauer spectra contain central para- magnetic line at the temperatures much lower than Curie point. It was assumed that this central line is due to antiferromagnetic phase with the Nee1 point lower than the temperature of measurements. The studies of magnetization made by Chikazumi [3], in particular on some Fe-Pt-Re alloys proved the existence of sharp drop of magnetization in very narrow band of external electrons' concentration (the number of electrons in open shells per atom).

In the present investigation the measurements of Mossbauer effect on Fe57 were performed in the ter- nary alloys Fe,,[Pt, -,(Rh, Re),],, where xvaries from 0 to 10 %. The third component concentration 0, 3, 5 and 10 % was chosen to pass through the critical value of external electrons' concentration.

The measurements were performed on conventional Mossbauer spectrometer with multichannel analyser, working in the constant acceleration mode. The source was Co57 in stainless steel. The alloys investigated were prepared by alloying the pure metals in an arc furnace in the atmosphere of purified Ar. The purity of components was not worse than 99,9 %,. Iron was used with natural abundance of FeS7.

The X-rays analysis of the specimens proved that they were homogeneous single phased with face- centered cubic lattice.

Besides the measurements of Mossbauer spectra there were performed the measurements of intensity of central line y-photons with the motionless source and adsorber. These measurements permitted to accomplish with high accuracy the magnetic phase analysis of the specimens. The temperature depen-

dence of magnetization was also measured by conven- tional balance technique. Figure 1 shows the Moss- bauer spectra of binary alloy Fe,,Pt,, and ternary alloys with 3, 5 and 10 % of Rh. The binary alloy spectrum consists of well resolved conventional sixtet

Fe, Pt-.. Rhs /r(.1o2

FIG. 1. - Mossbauer spectra of Fe70(Ptl-,Rhz)30 alloys

x =

0, 3, 5,

"/,

with broadened lines. There exists also a weak central line, corresponding to small amount of paramagnetic phase. The remarkable feature of 3 and 5 % Rh alloys spectra is the splitting of lines, which is most pro- nounced in 5 % Rh alloy. The intensity of central line increases with Rh concentration. In the alloy containing 10 % Rh the central line dominates in the

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19711398

C 1 - ¹¹¹⁸ P. STETSENKO, S. ANTIPOV, V. SATBAJEV

spectrum, the intensity of split lines getting quite but intensive central line is present already in 5 % Re weak. The spectra of Fe7,(Pt, -,Rex)3o alloys, shown alloy, and at 10 % Re the intensity of split lines is alre- in figure 2 have in essential the same peculiarities, ady so weak that they disappear in the noise. Figure 3 shows the temperature dependence of resonance line

l,f.

y-photons which went through the motionless adsorber

-800

(specimen) for Fe,,Pt,, and Fe70Pt,5Rh5. It is clear

from the curves that alloys contain two magnetic ordered phases. In the opposite, the temperature dependence of magnetization does not show any ano- malies. The values of effective magnetic field on ~e~~

nuclei H' and H" calculated for split lines of Fe70(Ptl -xRhx)30

alloys spectra are shown in figure 4 for different values of x.

Hn (ka) Fe,, P ~ M J

Rhr

t

3001

280 760

-1270

260

2LO 73cF

-230

Vrnrnls 220

-6 -1 -2 0 *2 +4 +6 *8

----L--L-C

FIG. 2. - Mossbauer spectra of Fe70(Ptl-rRhz)30 alloys

x%

x =

0, 3, 5, 10 %

FIG. 4. - The effective magnetic fields on Fe57 nuclei in Fe-ro(Pt~-zRhz)30 versus concentration of Rh.

There is no common view-point at present on the origin of magnetic properties of invar alloys, but in several theoretical and experimental works was assumed the coexistence of ferro- and antiferromagne- tic phase in these alloys [I, 21. Weiss [4] proposed the idea about the existence of two electronic states in y-iron which may correspond in invars to the two magnetic phases mentioned above. To explain the unusually high values of electron specific heat in iron- nickel invars Beck [ 5 ] also assumed the coexistence of ferro- and antiferromagnetism.

Thus the existence of two values of effective magnetic field on Fe5, in our alloys may be the direct sequence of the presence in these alloys both ferro- and anti- ferromagnetic states, at the temperature of measure- ments. It is also confirmed by the temperature depen- dence of resonance line y-photons intensity shown in figure 3. The maxima between critical points on these curves may be caused by orienting influence of long-

220

uo

- range exchange interaction between dispersed ferro- FIG. 3. - Temperature dependence of resonance line photons magnetic phase and disordered spins of antiferro-

intensity, passing through the motionless absorber. magnetic phase above Nee1 point.

References

[I] KONDORSKY (E. I.), SEDOV (V. L.), J. Appl. Phys., [3] CHIKAZUMI (St) et al., J. Appl. Phys., 1968, 39, 939.

1960, 31, 3315. [4] WEISS (R. J.), Proc. Phys. Soc., 1963, 82, 281.

[2] NAKAMURA (J.) et al., Proceed. of the Intern. Conf. on [5] BECK (P. A.) et al., J. Phys. Chem. Solids, 1964,25, 73.

magnetism., 1964, p. 144.