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Submitted on 1 Jan 1979
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MÖSSBAUER EFFECT STUDY OF Cr1-xFex ALLOYS
H. Kuwano, K. Ôno
To cite this version:
H. Kuwano, K. Ôno. MÖSSBAUER EFFECT STUDY OF Cr1-xFex ALLOYS. Journal de Physique
Colloques, 1979, 40 (C2), pp.C2-196-C2-197. �10.1051/jphyscol:1979269�. �jpa-00218667�
MOSSBAUER EFFECT STUDY OF Cr. Fe ALLOYS 1 -x x
H. Kuwatio and K. Ono
Miworan Institute of Technology,, Misumoto, Murovan, Hokkaido, Japan
* Institute for Solid State Physios, The University of Tokyo, Roppongi, Minatoku, Tokyo, Japan
Abstract.- A Mossbauer effect study has been carried out to investigate a magnetic behavior of Fe atoms in CrFe alloys in a concentration range from x=0.033 to 0.187. The internal field at 57Fe nuclei has been measured from 1.7 to 300 K. Magnetic transition temperatures associated with Fe-Cr and Fe-Fe interactions are determined from the temperature dependence of the half width of Moss- bauer spectra. It is concluded that two states of Fe atoms, namely, ferromagnetically interacting state with other Fe atoms and weakly interacting state with antiferromagnetic Cr atoms, coexist' at 1.7 K in the concentration range from x=0.033 to 0.133.
1. Introduction.- The internal field at 57Fe nuclei in CrFe alloys changes linearly from a value of 340 kOe for x=l to 130 kOe for x=0.1 at 4.2 K IM.
However, an abnormally small field of 35 kOe is ob- tained for the alloys with concentrations less than x=0.05 /2/, despite a large localized magnetic mo- ment of ••^Uj, of Fe atoms /3/.
Herbert et al. explained the small hyperfine field by a spin compensated state similar to the Kondo effect HI. The purpose of this work is to obtain more detailed information about the magnetic behavior of Fe atoms in CrFe alloys.
2. Experimental.- 10 mCi 57Co in Rh was used as a Mossbauer source. Absorbers were filed powders quen- ched from 1300 K into water with ice. Temperatures were detected by a Au(0.07% Fe)-Chromel thermocou- ple and controlled with errors less than i 0.4 K during measurements.
3. Results and Discussion.- Figure 1 shows three typical examples of the temperature dependence of the full width of the half maximum (FWHM) of Moss- bauer spectra. The FWHM changes in three or four
stages as marked by I-IV, and Ti-T., indicate tran- sition temperatures around each of which a rapid increase occurs in the FWHM. These temperatures are shown in figure 2 as functions of x. The temperature Ti agrees well with the Neel temperature T„ of Cr determined by neutron diffraction / 4 / and electrical resistivity measurements /5/. According to the phase diagram presented by Ishikawa et al. / 4 / , there is
a magnetic transition between commensurable antifer- romagnetic state and transverse sinusoidal state at the temperature T in the concentration range from x=0.02 to 0.04. The temperatures Xz agree with T in the above range of x, and extend to higher con- centrations up to x=0.13.
As for T3, any magnetic transitions or any anomalies in other physical properties have not been reported so far around them. The present results suggest that there is some kind of interaction between Fe atoms Fig. 1 : Temperature dependence of the FWHM of the absorption spectra. The inset is shown with a ma- gnified scale. 0Cro.967Fe0.033 © Cro.g32Feo.068
0 Cr0.87Fe0.i3-
JOURNAL DE PHYSIQUE Colloque C2, supplément au n° 3, Tome 40, mars 1979, page C2-196
Résumé.- On a étudié par effet Mossbauer le comportement magnétique des atomes de fer dans Çri-xFex (0,33 <? x < 0.187). Le champ interne sur le 57Fe a été mesuré de 1,7 à 300 K. Les températures de transition magnétique associées aux interactions Fe-Cr et Fe-Fe sont déterminées à partir de l'in- fluence de la température sur la largeur des pics du spectre Mossbauer. On en conclut qu|il existe deux états du fer à 1,7 K pour ce domaine de concentration, à savoir un état ferromagnétique entre atomes de fer et un état faiblement antiferromagnétique entre fer et chrome.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979269
and antiferromagnetic Cr matrix below T3 for the reason mentioned later.
Concent r a t i on, x
Fig. 2 : concentration dependences of T I , T2, T 3 , TI,, TN, Tco and Tc. @ ref. 141, ~ e f . /5/, O ~ e f 161
, 0
Ref. 171, A ~ e f 181.The saturation internal fields associated with the four stages mentioned above are estimated from the FWHM of absorption spectra and presented in figure 3 with symbols I-IV as functions of x.
- 1
,, 1
0 0.1 0.2
C o n c e n t
rat
i on,xF ? ~ . 3 : Concentration dependences of the internal field.
0,u,
A,0,
values estimated from the FWHM of the spectra.A,
values estimated from the width of the absorpt'ion at the bottom.0,
Ref. /I/.The stages I, 11 and 111 have two characteristics common to them : (a) the temperatures TI, Tp and T3 decrease 10-18 K per atomic percent increase in Fe concentration, which is the same order of the concentration dependence of TN 121, and (b) the sa- turation internal fields at these stages are inde-
pendent of the concentration x as shown in figure 3.
Therefore, the internal fields at these stages may be ascribed to the magnetic interaction between Fe atoms and Cr matrix. It should be noted that the in- ternal field at stage 111 amounts to about 30 kOe, which is the same order of that obtained in dilute
CrFe alloys 121. On the contrary, the stage IV -
shows a quite different trend : (a) the temperature TI, increases with increase of x, approaching the Curie temperature T determined by magnetization measurements 161. (b) the saturation internal fields
at stage IV measured at 1.7 K, increase with increa- se of x as shown in figure 3. So, the stage is cha- racterized by the ferromagnetic interaction between Fe atoms. In figure 3, solid triangles indicate the internal fields estimated from the width of absorp- tion spectra at the bottom measured at 1.7 K, which mean the highest internal field. These points loca- te near the dotted line which is extrapolated from the concentration region where Fe atoms show the ferromagnetic behavior. In the case of x=0.033, two states of Fe atoms coexists at 1.7 K : one consists of ferromagnetically ordered Fe atoms interacting with one another and showing a large internal field of about 90 kOe, and the other consists of Fe atoms weakly interacting with antiferromagnetic Cr matrix.
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