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Mössbauer study of a nanocrystalline FeCr-based metallic glass
iissbauerstudyof a nainccrystalline Fe-Cr-based
ic
E. Jqdrykaapbp * , IV.Randtianantoandm a,J.M. Gaenikhe‘, A. slaw H.K
L#achowicz
b
’ Equip de Physique de I%tat C-4 U&l CNRS 807,lJniuersit6 dsr Mae F72017 Le b Insitute of Pkysics, Polish Academy of Sciences, AL Lomtk&v 32/#,02 &6%WQ~QWQ, Abstract
Wssbauer spectroscopy has been performed over the temperature range 4.2-833 K in t Fe,CrsCuNb&B, metallic glass. The sample was found to consist of a
This study is CAncerned with a nanocrystalline material in which classical FINEbET composition has been modified to be Fe,CrsCuNb,Si,,B,. The addition of chromium lowers the Curie point of the amorphous phase and the mean value of its hyperfine field [lb thus allowing a temperature dependent study with microscopic methods such as Wssbauer spectroscopy. Previous magnetization measurements have showu that the metallic glass of this composition displays a superparamagnetic behaviour in samples with low volumetric fraction of nanocry&lites [2]. The aim of this work is to study the aynamics of this process by performing a detaZed Kksbauer study as a function of temperature on the as-quenched its wril as nanocrystalliied samples. As a reference, a classical FINEMET has also been studied and the results obtained fully agree with those reported elsewhtre [3]. The metglass Fe,CrsCuNb,Si,,B, has been prepared by a single Teller melt-spinning technique in the form ef a ribbon 5 mm wide and 25 pm thick. The as-quenched metallic glass was annealed under vacuum at T, = 803 K during 20 min with a heating ;ate of 5 K/mm. The M%sbauer experiments were performed in a transmksion geometry, over the kmperature rang; 3.2-633 K, usin! a constant acceleration dignal spectrometer with a Co source diffuwd into a 3todium matrix. The sample which con&s of 4 cm2 sheets of ribbon was located -under vacuum either in a bath cryostat or in a furnace. The evolution of Mssbauer spectra as 8 function of temperature is presented in Fig. 1. The spectra exhibiting a complex hyperfine structure can be decomposed in two components which display a very different temperature
l
Corresponding
author. Fax: +4%X&43
behaviour: (i) in the low v&city range a sexte? and overlapping lines for asymmetric doublet for T sextet, the resolution of which being str dependent. The inner component is a main@ amorphous matrix whereas from the crys!!iue precipitates. TKe de procedure +ll be report&d elsewhere. Fig. 2 illustrates the hype
amorphous
samples where a
ble on the low-5eld side may indicate of lotA environment. Sii chro shoulder to the chromium
09 26; mail:
jedry@~ammal.ifpan.edu.pl. 03W8853/95/%oFSO 0 1995 Elsevier science B.V. Al rights reserved SSLIlO304-8853(94)01234-2
b
9
i of.Wagwi.wn atad Magnetic Materials MO-144 (1995) 451-452
of hyperfine fielddistribue~v~~eo~ in the amorental fac& indicate that the build-up of crystalline segregation during crystalliza-
10
field distriiution in both, of the heat treated sample n of temperature in Fig. 3. The otpho~~~ phase derived from m the %-quenched sampia 415 evidence for the relative the amorphous matrix
2 0 0
10 20 30 HYPERFINE FIELD (T)
40
Fig. 2. Distribution of hypertine fields at room temperature in Fe,Cr,CuNb,Si,,B,, before and after heat treatment.
0
200
400 TEMPERATURE
600
800
1000
(W)
Fig. 3. Temperature evolution of the mtan hyperfine field in heat treated Fe,Cr,CuNb,Si !,B,.
after the heat treatment. Unfortunately, the Curie temperature of the crystalline phase cannot be evidenced because the time required to record the Mijssbauer spectra at high temperatures would result in a further annealing treatment leading to a structural and compositional evolution of the crystals. In conclusion, the present study gives a microscopic insight into the crystallization process of these materials. In particular, we were able to demonstrate the phase segregation during the crystallization and the absence of chromium in the nanocrystalline phase. Further studies, involving additional heat treatment and variation of composition are under way. References
-6
0
+6
-t-3 recoded at dierent temPerametaRic glass after heat treatment
[I] ST. Lia, L.Y. Jang and D.P. Chiang, J. Phys. F 17 (19g7!7) 1231. [2] A. Slawska-Waniewska, M. Gutowski, HR. Lachowicz, T. Kulik and H. Matyja, fhys. Rev. B 46 (1992) 14594. [3] G. Rixccker, P. Schaaf and U. Gonset, J. Phys.: Coadens. Matter 4 (1992) 10295. [4] G. Rixecker, P. Schaaf and U. Gonser, Phys. Stat. Sol. (a) 139 (1993) 309.
ic
E. Jqdrykaapbp * , IV.Randtianantoandm a,J.M. Gaenikhe‘, A. slaw H.K
L#achowicz
b
’ Equip de Physique de I%tat C-4 U&l CNRS 807,lJniuersit6 dsr Mae F72017 Le b Insitute of Pkysics, Polish Academy of Sciences, AL Lomtk&v 32/#,02 &6%WQ~QWQ, Abstract
Wssbauer spectroscopy has been performed over the temperature range 4.2-833 K in t Fe,CrsCuNb&B, metallic glass. The sample was found to consist of a
This study is CAncerned with a nanocrystalline material in which classical FINEbET composition has been modified to be Fe,CrsCuNb,Si,,B,. The addition of chromium lowers the Curie point of the amorphous phase and the mean value of its hyperfine field [lb thus allowing a temperature dependent study with microscopic methods such as Wssbauer spectroscopy. Previous magnetization measurements have showu that the metallic glass of this composition displays a superparamagnetic behaviour in samples with low volumetric fraction of nanocry&lites [2]. The aim of this work is to study the aynamics of this process by performing a detaZed Kksbauer study as a function of temperature on the as-quenched its wril as nanocrystalliied samples. As a reference, a classical FINEMET has also been studied and the results obtained fully agree with those reported elsewhtre [3]. The metglass Fe,CrsCuNb,Si,,B, has been prepared by a single Teller melt-spinning technique in the form ef a ribbon 5 mm wide and 25 pm thick. The as-quenched metallic glass was annealed under vacuum at T, = 803 K during 20 min with a heating ;ate of 5 K/mm. The M%sbauer experiments were performed in a transmksion geometry, over the kmperature rang; 3.2-633 K, usin! a constant acceleration dignal spectrometer with a Co source diffuwd into a 3todium matrix. The sample which con&s of 4 cm2 sheets of ribbon was located -under vacuum either in a bath cryostat or in a furnace. The evolution of Mssbauer spectra as 8 function of temperature is presented in Fig. 1. The spectra exhibiting a complex hyperfine structure can be decomposed in two components which display a very different temperature
l
Corresponding
author. Fax: +4%X&43
behaviour: (i) in the low v&city range a sexte? and overlapping lines for asymmetric doublet for T sextet, the resolution of which being str dependent. The inner component is a main@ amorphous matrix whereas from the crys!!iue precipitates. TKe de procedure +ll be report&d elsewhere. Fig. 2 illustrates the hype
amorphous
samples where a
ble on the low-5eld side may indicate of lotA environment. Sii chro shoulder to the chromium
09 26; mail:
jedry@~ammal.ifpan.edu.pl. 03W8853/95/%oFSO 0 1995 Elsevier science B.V. Al rights reserved SSLIlO304-8853(94)01234-2
b
9
i of.Wagwi.wn atad Magnetic Materials MO-144 (1995) 451-452
of hyperfine fielddistribue~v~~eo~ in the amorental fac& indicate that the build-up of crystalline segregation during crystalliza-
10
field distriiution in both, of the heat treated sample n of temperature in Fig. 3. The otpho~~~ phase derived from m the %-quenched sampia 415 evidence for the relative the amorphous matrix
2 0 0
10 20 30 HYPERFINE FIELD (T)
40
Fig. 2. Distribution of hypertine fields at room temperature in Fe,Cr,CuNb,Si,,B,, before and after heat treatment.
0
200
400 TEMPERATURE
600
800
1000
(W)
Fig. 3. Temperature evolution of the mtan hyperfine field in heat treated Fe,Cr,CuNb,Si !,B,.
after the heat treatment. Unfortunately, the Curie temperature of the crystalline phase cannot be evidenced because the time required to record the Mijssbauer spectra at high temperatures would result in a further annealing treatment leading to a structural and compositional evolution of the crystals. In conclusion, the present study gives a microscopic insight into the crystallization process of these materials. In particular, we were able to demonstrate the phase segregation during the crystallization and the absence of chromium in the nanocrystalline phase. Further studies, involving additional heat treatment and variation of composition are under way. References
-6
0
+6
-t-3 recoded at dierent temPerametaRic glass after heat treatment
[I] ST. Lia, L.Y. Jang and D.P. Chiang, J. Phys. F 17 (19g7!7) 1231. [2] A. Slawska-Waniewska, M. Gutowski, HR. Lachowicz, T. Kulik and H. Matyja, fhys. Rev. B 46 (1992) 14594. [3] G. Rixccker, P. Schaaf and U. Gonset, J. Phys.: Coadens. Matter 4 (1992) 10295. [4] G. Rixecker, P. Schaaf and U. Gonser, Phys. Stat. Sol. (a) 139 (1993) 309.