Hine, Shiro

Shigematsu, Toshihiko

Takada, Toshio

Kyoto University Research Information Repository

Title Mössbauer Studies on Supersaturated FeSb Solid SolutionsAuthor(s)Shigematsu, Toshihiko; Hine, Shiro; Takada, ToshioCitationBulletin of the Institute for Chemical Research, KyotoUniversity (1979), 57(4): 306-309Issue Date1979-10-15URL http://hdl.handle.net/2433/76841RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityBull. Inst. Chem. Res., Kyoto Univ., Vol. 57, No. 4, 1979  MOssbauer Studies on Supersaturated FeSb Solid Solutions                     Toshihiko SHIGEMATSU, Shiro HINE,                          and Toshio TAKADA*                             ReceivedJuly 9, 1979    The hyperfine field at iron sites in supersaturated FeSb solid solution was determined by Moss-bauer effect. The mean hyperfine field H decreases with increasing Sb content at a rate of dH/dc= —101 kOe. The maximum hyperfine field seems to be concentration dependent. The obtained values of Hmax are 333 kOe for 4 at%Sb and 355 kOe for 17 at%Sb. The obtained values of dH/dc and Hmax in our measurement are qualitatively in agreement with those obtained by Vincze and Aldred for dilute FeSb solid solution.    KEY WORDS: Magnetic hyperfine field / Bcc alloy /                          INTRODUCTION    The MOssbauer study on a-Fe solid solutions with non-transition atoms is of interest in understanding the influence of surrounding solute atoms on the local changes of magnetic hyperfine field. From this point of view, many investigations have been studied for several alloy systems.1-5) The Mossbauer spectra were satisfactorily accounted for with assuming the random distribution of solute atoms and impurity effect being localized. Namely the magnetic hyperfine field of Fe atom depends on the number of solute atoms only at the first and the second nearest neighbor sites.    According to Vincze and Aldred,5) Al and Si, and Ga, Ge, As, Sn and Sb seem to belong to different groups with regard to the concentration dependence on the hyperfine field Ho corresponding to the site without impurity neighbors, and the concentration dependence of bulk magnetization dp/dc. In the case of FeSb alloy system, no information was obtained on the local changes of magnetic hyperfine field at 57Fe nuclei which are surrounded by many Sb atoms, because of the limitation of the equilibrium solid solubility of Sb in a-Fe (-4 at%) at room temperature.6) We produced metastable FeSb alloy films by simultaneous vapor depositions of Fe and Sb onto acetylcellulose sheets maintained at room temperature, and obtained supersatu-rated bcc Fe solid solutions with 0-29 at%Sb7). In the present paper, we report the study of magnetic hyperfine field at 57Fe nuclei in supersaturated bcc FeSb alloys by Mossbauer effect.                            EXPERIMENTAL    Bcc FeSb alloy films were produced by simultaneous vapor depositions of Fe and Sb onto acetylcellulose sheets maintained at room temperature as was described * Ifk Ilg, Hav[s, jffl!J: Laboratory of Solid State Chemistry, Institute for Chemical   Research, Kyoto University, Uji, Kyoto 611. (306 ) Mossbauer Studies on Supersaturated FeSb Solid Solutions   • '') t''''''. r.. • . - . 1-7.-          )    i~I ?----------------------------------- 4— • 50-        '-'T 0--------------------------------      2417 20                                                                               • = 0         a24                          201'                            0'''110~                                      —_ J•;' ,j29  •••29                                              20 1 I I I I I I I I 0 .''111'111111Mwo -8 -6 -4 -2 0 2 4 6 8 350 300 250 200             Velocity (mm/s)H (k0e)Fig. 1. Fitted (solid line) and experimental spectra Fig. 2. Hystograms of the probability       from 4 to 29 at%Sb at 295 K.of hyperfine fields giving the                                                          fitted curves in Fig. 1.330'§.  320- \•.:r •N't; 0310-1 . I=I\ 300-IF-.•  I II I I I I I I I I I     0 0.10 0.20 0.30 -8 -6 -4 -2 0 2 4 6 8            CVelocity (mm/s) Fig. 3. Dependence of mean hyperfine field Fig. 4. Fitted spectra including a paramagnetic H on Sb content at 295 K.doublet (oxide phase with I.S.=0.32        0; present experiment, •; Vinczemm/s and dE=1.0mm/s) of 17 at%Sb    and Aldred.5)at 295 K. (307)                                      T.  SHTGEMATSU, S. HINE, and T. TAKADA         in the previous paper.7) Mossbauer effect measurements were made at 295 K using         a conventional spectrometer. 57Co embedded in copper matrix was used as a source.        The velocity scale was calibrated by using an iron foil as the standard absorber.            The typical Mossbauer spectra taken at 295 K are shown in Fig. 1. On each        spectrum we have performed a fitting by a superposition of several steps of the six        Lorentzians with different Zeeman splittings ranging from the maximum hyperfine        field Hmax in the steps of 15 kOe. In addition the followings were assumed: (a) the        isomer shift varies slightly. It is 0.00 mm/s at Hmax and increases with Ai mm/s for        each step, (b) there is no quadrupole effect, (c) the line width is 0.32 mm/s. The        resulting P(H) curves are shown in Fig. 2. The fitted curves are shown as the full        line in Fig. 1. In this case we used di=0.032 mm/s. The mean hyperfine fields H(c) obtained by this fitting are present in Fig. 3. In some spectra, a quadrupole        splitting paramagnetic doublet due to oxide phase was superposed on the magnetic        hyperfine spectrum. The typical fitting curve including the oxide phase is shown        in Fig. 4. In this spectrum the portion of the oxide phase was 17% and the observed Mossbauer parameters are I.S.=0.32 mm/s and dE=1.00 mm/s. This oxide phase        shows hyperfine spectrum at 4.2 K with H=480 kOe. Analysis on the results at        4.2 K was not attempted since the reduction of oxide fraction is actually unreliable.                                     DISCUSSION            The field Hmax is found to be concentration dependent. The obtained values        of Hmax are 333 kOe for 4 at%Sb, 35.5 kOe for 17 at%Sb and 350 kOe for 24 and        29 at%Sb. The similar behavior was observed by Vincze and Aldred') for dilute        bcc FeSb solid solution. In their case, they fitted the spectra by the assumptions        that only the first and second neighbor effects are resolvable in the Mossbauer spectra        and the multiple impurity neighbor effects are additive. The hyperfine field at         iron atoms with no neighbor impurities, Ho depends slightly on the concentration.        The value of Ho increases from 331 kOe for 2.4 at%Sb to 333 kOe for 4.4 at%Sb.        The value Hmax may correspond to Ho for the cases of 4 and 17 at%Sb. While, Hmax        does not correspond to Ho for the cases of 24 and 29 at%Sb, because the probability         of occurrence for a configuration with no neighbor impurities is quite small. Hmax        for the cases of 24 and 29 at%Sb probably corresponds to the hyperfine field at iron         atoms with one neighbor impurity. The obtained values of Hmax in our measurement        are closely connected to those obtained by Vincze and Aldred for dilute FeSb solid        solution. The hyperfine field at iron atoms with no neighbor Sb atom increases         with increasing Sb content.            The value of H decreases linearly with increasing composition c at a rate of dH/        dc= —101 kOe. Vincze and Aldred') obtained the value of dH/dc which changes        with composition from —130 kOe for 2.4 at%Sb to -105 kOe for 4.4 at%Sb.            It was found for FeAl alloys that Ho is constant and H decreases with increasing        Al content at a rate of dH/dc= —200 kOe.6) Al impurity atoms act more or less         like non-magnetic holes in the bcc Fe. In contrast, an increase was found in the        magnetic moments of Fe with dissolving Sb. To use the value of Hmax and the         proportionality assumed 2.22 /2B=330 kOe, we can estimate the magnetic moment of (308 ) Mossbauer Studies on Supersaturated FeSb Solid Solutions Fe atoms which have no neighbor Sb impurities. It is 2.51 / B for 17 at% Sb. Similar behavior was observed in FeGa,4) FeGe,5> and FeSn5> solid solutions. The atomic radii of Sb, Ga, Ge, and Sn are larger than that of Fe and the lattice parameter of bcc Fe solid solutions with those solute atoms increases with increasing composition.8) This leads to the expansion of metal-metal distance in the bcc matrix. As is well known, the exchange integral J depends on the atomic distance (Bethe curve). The value of J increases when the atomic distance of bcc Fe is expanded. This may lead to the increase of magnetic moment of Fe atoms with no neighbor Sb in FeSb solid solution.                             REFERENCES (1) G. K. Wertheim, V. Jaccarino, J. H. Wernick, and IL N. E. Buchanan, Phys. Rev. Lett., 12,    24 (1964). (2) P. A. Flinn and S. L. Ruby, Phys. Rev., 124, 34 (1961). (3) M. B. Stearns, Phys. Rev., 147, 439 (1966). (4) L. R. Newkirk and C. C. Tsuei, Phys. Rev., B4, 4046 (1971). (5) I. Vincze and A. T. Aldred, Phys. Rev., B9, 3845 (1974). (6) M. Hansen, "Constitution of Binary Alloys," 2nd ed, McGraw-Hill, New York, 1958, p. 708. (7) T. Shigematsu, T. Shinjo, Y. Bando, and T. Takada, Bull. Inst. Chem. Res., Kyoto Univ., 57, 310 (1979) .(8) W. B. Pearson, "A Handbook of Lattice Spacings and Structures of Metals and Alloys," Vol. 1,     Pergamon Press, New York, 1958. ( 309 )

Mössbauer Studies on Supersaturated FeSb Solid Solutions

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Mössbauer Studies on Supersaturated FeSb Solid Solutions

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