THE MAGNETOSTRICTION AND MAGNETIC BEHAVIOUR OF AMORPHOUS (Fe80-xRx) B20 (R = Y, Ce, Nd, Sm, Gd, Dy, Ho, Er, Tm Lu) (0 < x < 10) R. Grössinger, H. Sassik, R. Wezulek, T. Tarnoczi

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R. Grössinger, H. Sassik, R. Wezulek, T. Tarnoczi. THE MAGNETOSTRICTION AND MAG- NETIC BEHAVIOUR OF AMORPHOUS (Fe80-xRx) B20 (R = Y, Ce, Nd, Sm, Gd, Dy, Ho, Er, Tm Lu) (0 < x < 10). Journal de Physique Colloques, 1988, 49 (C8), pp.C8-1337-C8-1338. ￿10.1051/jphyscol:19888611￿. ￿jpa-00228836￿

HAL Id: jpa-00228836 https://hal.archives-ouvertes.fr/jpa-00228836 Submitted on 1 Jan 1988

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THE MAGNETOSTRICTION AND MAGNETIC BEHAVIOUR OF AMORPHOUS (Fego-xRz) B20 (R = Y, Ce, Nd, Sm, Gd, Dy, Ho, Er, Tm Lu) (o< x

R. Grossinger (I), H. Sassik (I), R. Wezulek and T. Tarnoczi (2)

(I) Inst. j. Experimentalphysik, Techn. Uniu. Viehna, Austria (2) KFKI Budapest, Hungary Abstract. - Amorphous ribbons of the composition (Feso-,Rx)B20 (R = Y, Ce, Nd, Sm, Gd, Dy, Ho, Er, Tm, Lu) (0 < s < 10) were produced. The behaviour of the magnetisation can be explained assuming an asperomagnetic type of order. The magnetostriction decreases with increasing R-concentration for all rare earth elements studied here.

Introduction Results and discussion

Fe80B20 is a well known soft magnetic amor- The concentration dependence of the saturation phous material with a high saturation induction magnetization for (Fe80-,R,) B2o is shown in figure 1 (I, = 1.6 T) and an unusual high positive magne- for R = Ce, Nd, Sm, Gd, and in figure 2 for R = Dy, tostriction (A, = +34 x lod6) . A small ("zero" ) mag- Ho, Er, Tm. In both cases M, decreases with the con- netostriction causes a low in soft magnetic materials. The systems (Feso-,Rx) B20 (R = Y, Ce, Nd, Sm, Gd, Dy, Ho, Er, Tm, Lu) (0 < x < 10) were investigated in order to study how the rare earth ele- ment substitution influence the magnetostriction. Rare earth elements exhibit generaly large magne- tostrictive effects because of their orbital moment. It is therefore a hope that a small amount of a rare earth substitution is sufficient to obtain a compound with zero magnetostriction.

Experimental

A set of ribbons of the composition (Feso-,R,) B~o (0 < x < 10) was produced by the single roller tech- nique under He atmosphere (p = 500 mbar). The amorphous state of the ribbons was tested by X-rays Fig. 1. - Saturation magnetization as a function of x of the but also by optical microscopy. No evidence of crys- ribbons with the composition (Feso-,R,) B2o (R = Ce, Nd, talline inclusions was detected. Sm, Gd) as determined at room temperature. The loop was measured at room temper- ature using a hysteresograph as published by O'Dell 111. This hysteresograph produces external fields up to 1 200 A/m. This field is not sufficient to saturate the samples. The saturation of some selected ribbons was therefore determined using a Faraday balance in an external field of 48 kA/m. The saturation value as determined at a field of 400 kA/m was within the experimental error the same. Due to the geometry of amorphous ribbons (length >> width >> thickness) "special" techniques for deter- mining the magnetostriction were developed (see e.g. 2,3). Nearly all of them are based on the depen- dence of magnetic properties (like the coercivity or the susceptibility etc.). The most sensitive method is the SAMR (Small Angle Magnetization Rotation Method) Fig. 2. - Saturation magnetization as a function of x of the described by [4], which was applied here. With this ribbons with the composition (Feso-,R,) B20 (R = Dy, Ho, technique A, can be determined down to lo-'. Er, Tm) as determined at room temperature.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19888611 C8 - 1338 JOURNAL DE PHYSIQUE centration x. This is surprising if one assumes that the Table I. - Magnetostriction constants A, x as ob- magnetic moment of the light rare earth elements (LR) tained for Feso-,LB2o at room temperature. couples parallel to that of the Fe and the moment of the heavy rare earth elements (HR) couples antiparal- lel to the Fe moment, as usual in such compounds, if they are crystalline.

The temperature dependence of the magnetostric- tion in such amorphous ribbons can be explained as- suming a single ion (scaling with &?) as well as a two ion contribution (scaling with M:) [6]. Due to the as- peromagnetic type of order no simple scaling between A, and a certain power of M, can be expected. The coercivity of the ribbons in- or decreases depending on the rare earth element acting a3 a substituent. In a simple model Hc should scale with A, in soft mag- netic materials. In our case H, (x) could not be corre- lated with the concentration dependence of the mag- netostriction. Metallurgical parameters especially in- Fig. 3. - Saturation magnetization of FeT4&B20 as a func- trinsic stress centers may determine Hcalso. A better tion of the atomic number of the lanthanides. Note the insight about the origin of the magnetostriction as well dotted line of the corresponding mean value of the Y- and as about any correlation between A, and the coer- Lu-compound, which is usual as a reference. civity is possible if temperature dependent studies are available. Additionally the type of magnetic order in Figure 3 shows the magnetization of Fe74RsB20 ver- the rare earth substituted ribbons is still open. For sus the atomic number of the lantanides taking the this purpose additional experimemts like Mossbauer, mean value of the magnetization of the correspond- high field magnetization and temperature dependent ing compounds containing a nonmagnetic R-element magnetization studies are in progress. (Fe74LueB20 and Fe74Y6B20) as a reference line. This picture demonstrates that the light rare earths (LE) Acknowledgement couple with a ferromagnetic component whereas the heavy rare earth moments (HR) couple with a ferri- This work was supported by the Austrian "Fond magnetic component to the Fe-moment. However the zur Fiirderung der wissenschaftlichen Forschung in situation is not simple. The rather low magnetization dsterreich" Projekt Nr. 5020. values and in particular the reduction of M, in the case of the light rare earth indicate a noncollinear arrange- ment of the moments as was found for similar systems [5]. It is worth to note that the slope dM,/dx is ap- proximately -6 ~m~/k~/at%(at% ... atomic percent) for all light rare earth elements but -10 ~m~/k~/at% for all heavy rare earths indicating a different arrange- [I] O'Dell, T. H., IEEE Trans. Magn. MAG-17 ment of the magnetic moments. In all cases the order- (1981) 3364. ing temperature decreases with increasing R concen- [2] O'Dell, T. H., Phys. Status St~lidiA 68 (1981) tration, indicating a reduced exchange. These results 221. can be explained assuming a fan structure which is [3] Hilzinger, H. R., Hillmann, H., Mager, A., Phys. generally called asperomagnetism or sperimagnetism if Status Solidi A 55 (1979) 763. antiparallel coupling is involved. The magnetostriction [4] Narita, K., Yamasaki, J., Fukunaga, H., IEEE also decreases linearly with increasing amount of rare Trans. Magn. MAG-16 (1980) 435. earth. Plotting the value A, but also the slope dX,/dx [5] Ryan, D. H., Liao, L. X., Altounian, Z., Solid versus the rare earths gave no clear trend, which might State Cornmun. 66 (1988) 339. be also a consequence of the complex type of order. In [6] Madurga, V., Vazques, M., Hernando, A., table I the data for A,, as obtained at room tempera- Nielsen, 0. V., Solid State Cornmun. 52 (1984) ture, are given. 701.