MÖSSBAUER STUDY OF BORON FERRITES FeNi2BO5 AND FeNiBO4

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MÖSSBAUER STUDY OF BORON FERRITES FeNi2BO5 AND FeNiBO4

M. Abe, K. Kaneta, M. Gomi, S. Nomura

To cite this version:

M. Abe, K. Kaneta, M. Gomi, S. Nomura. MÖSSBAUER STUDY OF BORON FERRITES FeNi2BO5 AND FeNiBO4. Journal de Physique Colloques, 1979, 40 (C2), pp.C2-325-C2-326.

�10.1051/jphyscol:19792114�. �jpa-00218484�

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JOURNAL DE PHYSIQUE Col[oque C2, suppl4ment au n o 3 , Tome 40, mars 1979, page C2-325

MOSSBAUER

STUDY

OF BORON

FERRI TES

FeNi 2B05

AND

FeN iB04

M. Abe, K. Kaneta, M. Gomi and S. Nomura

Department of Physical EZectronics, Tokyo I n s t i t u t e of Technology, Ookayama, Meguro-Ku, Tokyo, Japan

Rdsumd.- Des mesures d'effet KGssbauer ("Fe) et d'aimantation ont 6tb rdalis6e.s sur des poudtes de microcristaux entre 4,2 et 300 K. Les spectres de relaxation magndtique de F ~ ~ + N ~ $ + B O ~ et Fe3+~i2+~0t, ont dt6 observds au-dessous de 102 et 26 K respectivement; ces tempdratures sont 6levbes en comparaison de la tempdrature N6el antiferromagn6tique (54 et 13 K) di5terminde par mesures ma- gnEtiques sur ces mSmes composds. ces particularitss ont pu Stre attribuges B la faible port6e de l'interaction magndtique dans ces compos6s.

Abstract.- Mgssbauer ("Fe) and magnetic measurements were performed on powdered single crystals at 4.2 % 300 K. Magnetic relaxation spectra were observed for FeNi2BOs and FeNiBOt, below 102 and 26 K respectively, which are much higher than the antiferromagnetic Ndel temperatures (i.e. 54 and 13 K) determined by the magnetic measurement for the respective compounds. These features may be ascribed to the low dimensional nature of the magnetic interaction in the compounds.

The preparation and X-ray structural analysis of the two boron ferrites F~'''M:~Bo~ (or Fez03 .B203.

&NO, where M Fe, CO, Ni, Cu) and F~IIIM'IBo~, (or FezOs.B203. 2M0, where M = Fe, CO, Ni, Mg) were re- ported by Bertaut et al. in 1950 / l , 2 / . Both have orthorhombic crystal cells in which the Fe3+ and M

'+ ions are located on the distorted octahedral in- terstices of the oxygen ions. The octahedra are stacked along the c axis sharing edges., while they share edges and corners in the ab plane in which the I

nonmagnetic boron ions make B03 triangles. It is then expected that the magnetic interaction in these compounds are strong along the c axis and weak in the ab plane having low dimensional nature. There- fore the magnetic properties of the boron ferrites are of interest, which have, however, not been stu- died in detail at present /3,4,5/. It may be partly because of the difficulty in obtaining the sample in single phase without ferromagnetic impurity. In this paper, we describe the gssbauer and magnetic measurements on FeNizBOsand FeNiBOt, crystals which were successfully grown in single phase within the limitation of X-ray analysis by means of CVT method using H C 1 carrier gas. Both measurements were done on powdered single crystals below room temperature, using a constant acceleration Mgssbauer spectrometer and a vibrating sample magnetometer.

It was found that the sample of FeNizBOs was free from terromzgnetic impurity, since the magne- tization showed neither the remnant nor saturation against the external field, while that of FeNiBOt, exhibited a trace of ferromagnetic impurity which was, however, so small that the correction was not

made in the calculation of the magnetic susceptibility. As shown in figure 1 , the inverse susceptibility makes a broad minimum at about 54 K for FeNi2BOS and

13 K for FeNiBOt,, which may correspond to the antiferromagnetic Nbel temperatures.

Fig. 1 : Inverse magnetic susceptibility vs.temperature for FeNizBOs and FeNiBOt,.

Figure 2 shows the Mijssbauer spectra of FeNizBOs at various temperatures. The spectrum at the room temperature (285 K) is composed of a sharp quadrupole doubletwithQ.S.=1.17 m / s and I.S.nO.44 m / s (rela- tive to stainless steel), which can be ascribed to the ~ e ion located on one site with a strongly ~ + distorted environment, as expected from the crystal

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792114

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c2-326 ^JOURNALDE PHYSIQUE

structure : The amount of the site inversion concern- above the N6el temperature determined by the magne- ing Fe and Ni ions is considered to be negligibly tic measurement. These anomalous features observed small. The spectra between 111.2 and 100.5 K show in the two boron ferrites may be ascribed to the two unresolved magnetic Zeeman patterns with inner two dimensional nature of the magnetic interactions in lines, which change to broad 6-Line patterns with the compounds mntioned above.

further decrease of the temperature, and the NGel

temperature was tentatively determined as 102 4 K, FeNi BO, Velocit y(mm/s) where the Zeeman pattern was resolved into six

....

..;. . lines

.

. . .

. . . .

285K

.

_{. . .}

.

. . , .

. :' : '

Fig. 3 : Mijssbauer spectra of FeNiBOr at various temperatures.

References

/I/ Bertaut, F., Bochirol, L., Blum, P., C.R. Hebd.

Sban. Acad. Sci. (France)

2

(1950) 764.

/2/ Bertaut, F., Acta Cryst.

3

(1950) 473.

/3/ Chevallier, R., Mathieu, S., Girard, J., Bull.

Soc. Chim. (1948) 611.

/4/ Benoit, R., C.R. Habd. Sban. Acad. Sci. (France) 231 (1950) 1216.

/ 5 / Apostolov, A.V., Mihov, M.T., Cholakov, P.T., Horvat, M., C.R. Hebd. Sban. Acad. Sci. (Bulga- ria)

2

(1976) 1273.

Fig. 2 : Mijssbauer spectra of FeNizBOs at various temperatures.

It is noteworthy that the Nbel temperature is much higher than that determined by the susceptibility measurement (i.e. 54 K). As seen in the figure, the innermost two lines remain relatively narrow and the quadrupole splitting disappears at the low temperatures, which suggests the presence of magnetic spin relaxation. ~ s s b a u e r spectrum was taken for FeNiBOt, at 285 K, 8 0 K and 26 K, as shown in figure 3. Simi- lar to the case of FeNi2B05, a sharp quadrupole dou- blet of Fe3+ (Q.S.nO.71 mm/s and I.S.=0.53 m/s) is observed at room temperature, and a magnetic relaxation spectrum at 26 K, though the temperature is far