An influence of Si on the structural and magnetic properties of
Dy(Fe,V,Si)12 compounds is studied. X-ray diffraction shows that these materials
crystallise in the tetragonal ThΜn12-typae structure. An increase in the
saturation magnetization, the Curie temperatures and magnetocrystalline
anisotropy in the Si substitutional systems is observed when compared with
DyFeι2-xVx . The magnetic properties depend on the preferential site occupation
and concentration of Si and V atoms in these compounds

Chrobak, Artur

Drzazga, Zofia

Kaczorowski, D.

Winiarska, Anna

Acta Physica Polonica A

English

Repozytorium Uniwersytetu Śląskiego RE-BUŚ

             Title: Structural and magnetic properties of Dy(Fe,V,Si)12 compounds    Author: Zofia Drzazga, Anna Winiarska, Artur Chrobak, D. Kaczorowski    Citation style: Drzazga Zofia, Winiarska Anna, Chrobak Artur, Kaczorowski D. (1997). Structural and magnetic properties of Dy(Fe,V,Si)12 compounds. "Acta Physica Polonica. A" (Vol. 92, nr 2 (1997), s. 335-338).   Vol. 92 (1997)	 ACTA PHYSICA POLONICA A	 No. 2Proceedings of the European Conference "Physics of Magnetism 96", Poznań 1996STRUCTURAL AND MAGNETIC PROPERTIESOF Dy(Fe,V,Si)12 COMPOUNDSĜ. DRZAZGA, A. WINIARSKA, A. CHROBAKInstitute of Physics, University of SilesiaUniwersytecka 4, 40-007 Katowice, PolandAND D. KACZoROWSKIInstitute of Low Temperature and Structure ResearchPolish Academy of SciencesP.O. Box 937, Wroclaw 2, PolandAn influence of Si on the structural and magnetic properties ofDy(Fe,V,Si)12 compounds is studied. X-ray diffraction shows that these ma-terials crystallise in the tetragonal ThΜn12-typae structure. An increase in thesaturation magnetization, the Curie temperatures and magnetocrystallineanisotropy in the Si substitutional systems is observed when compared withDyFeι2-xVx . The magnetic properties depend on the preferential site occu-pation and concentration of Si and V atoms in these compounds.PACS numbers: 61.10.—i, 75.30.Cr, 75.30.Gw, 75.50.Gg1. IntroductionIron-rich intermetallic compounds of the ThΜn 1 2-type structure have beenproposed as inexpensive alternatives for permanent magnetic materials. It is knownthat the rare earths and iron do not form the binary RFe12 phase, a third element isnecessary to stabilize the tetragonal ThΜn12-type structure [1]. These compoundshave the composition RFe12-xΜxf in which M represents a nonmagnetic 3d ele-ment, for instance Ti, V, Cu or metalloid Si. Apart from the R elements and 3delements, which mainly determine the magnetic properties of the compounds, alsostabilizing elements contribute to the magnetic properties. The aim of this workis to study the influence of the substitution of Si instead of V on the magneticproperties of DyFe1 2-xΜx compounds.2. ExperimentalSamples of nominal composition DyFe10V2-xSix , DyFe9V3-xSix andDyFe8V4-xSix (x = 0.05, 1.0, 1.5, 2.0) were prepared by arc-melting. The sampleswere prepared in the sane way as those described in [2].The structure and homogeneity of these compounds were checked by X-raydiffraction and thermomagnetic measurements. Lattice parameters were measured(335)336 Z. Drzazga et al.using X-ray powder diffractometer Siemens 5000 with Cu Κ α radiation. Recordedlines were fltted with X-Pro fiłer (written by A. Kachel) and the HX61 programmewas applied to find exact values of the lattice parameters.Magnetic moment was studied at fields up to 5 Τ in the temperature range1.7 K to room temperature. Mágnetocrystalline anisotropy was investigated bymeans of ac susceptibility and torsion measurements in the temperature range77-293 K. The easy direction of cägnetization (BR-ID) was determined from X-raydiffraction of aligned powders. The most of the samples showed the easy c-axis atroom temperature. Thermomagnetic curves at high temperatures were measuredusing a FaradaΥ balance.3. Results and discussion ,All investigated compounds have the tetragonal ΤhMn12-type structure.Slight decrease in the α and the c parameters with the increase in Si contentwere observed but the Vegard law was not fulfllled (Fig. 1).The investigated compounds are ferrimagnets with the Curie temperatures.above room temperature. Plot of Τ  as a function of silicon concentration is pre-sented in Fig. 1. The values of  Τ  are almost unchanged for DyFe10V2-xSix butincrease in silicon-rich compounds of DyFe9V3-xSix and DyFe8V4-xSix . The Curietemperature for DyFe8V2Si2 is about 60 K higher than for DyFe8V4. Moreover, asshown in Fig. 2, the resultant magnetization increases with the. Si content. Assum-.ing that the magnetic moment of the Dy ions takes its  free-ion value (10μΒ) themagnetic moment of the Fe atoms can be calculated from the values of the satura-tion magnetization obtained at 1.7 K. The estimated moment on Fe atom increasesStructural and Magnetic Properties ...	 337markedly in DyFe12-x(V,Si)x systems when compared with DyFe12-xVx . This isattributed to the enhancement of the exchange interaction due to the replacementof V by Si atoms. The effect of substituted Si atoms is similar to that observed inDyFe12-x (V,C)x under carbon doping [2].The ac-initial magnetic susceptibility versus temperature curves ofDyFe10V2-xSi x (Fig. 3) shows strong anomalies which are shifted towards highertemperatures with increase in x.These peaks of ac-susceptibility correspond tospin reorientation due to ma.gnetocrystalline anisotropy competition between the3d and rare-earth sublattices. At room temperature the EMD is determined bythe Fe sublattice but at low temperatures the negative Dy anisotropy contribu-tions cause the spin reorientation transition. The torsion measurements confirmthe tilting of the EMD from the c-axis with lowering temperature. A cone order-ing of the magnetic moments is observed for all studied compositions at 77 K.Generally, silicon content increases temperature of the beginning of the spin reori-entation transition. The anisotropy constants reported for ΥFe10V2 and YFe10 Si 2are nearly the same [3]. It follows that magnetocrystalline anisotropy of dysprosium sublattice is enhanced because any essential changes in the 3d sublattices arenot expected. .The analysis of spin reorientation in compounds with lower concentrationof iron (e.g. DyFe0V3-xSix and DyFe8V2Si2) is more complicated. It should benoticed that metamagnetic behavior of resultant magnetic moment is observedat low temperatures (Fig. 2). Changes in the magnetization under the action ofau external field seem to indicate the spin-flip. It follows from Fig. 2 that thecritical fleld values depend on vanadium and silicon content in DyFe12-x (V,Si)xseries. The results of torsion measurements also demonstrate an influence of theapplied magnetic fleld on the magnetic arrangement in the studied compounds.338 	 Z. Drzazga el al.The EMD in DyFe9V3-xSix determined from torsion curves at 77 K in sufficientlysmall magnetic field is still the c-axis but markedly tilts from the c-axis in magneticfields higher than 0.4 Τ. Temperature and fleld dependence of the spin reorientationtransition are due to the varying the nonmagnetic Μ element concentration.The obtained results indicate that magnetic properties of DyFe12-xΜx de-pend on the stabilizing element Μ. In these compounds, three different crystal-lographic sites are available for the Fe and M atoms. The V atoms prefer the 8isites [3] whereas the Si atoms share the Si and 8f positions with the Fe atoms [4].The deeper analysis taking into account the various distribution of the Fe and Μatoms and its influence on the exchange and crystal field interactions responsiblefor magnetic behavior in the studied compounds will be done elsewhere.AcknowledgmentsAuthors are indebted to Professor R. Troc for making possible the mea-surements of magnetization at 1.7 K. This work is partly supported by grantNo. 2 P30224403.References[1]W. Suski, in: Handbook on the Physics αnd Chemistry of Rare Earths, Vol. 22, Eds.K.Α. Gschneidner, Jr., L. Eyring, Elsevier, Amsterdam 1996, Ch. 149, p. 143.[2] Z. Drzazga, A. Winiarska, W. Zarek, E. Popiel, L. Gladczuk, J. Alloys Comp. 230,76 (1995).[3] M. Solzi, L. Pareti, O. Moze, W.I. Dawid, J. Appl. Phys. 64, 5084 (1988).[4] C. Christides, M. Anagnostou, Hong-Shuo Li, A. Kostikas, D. Niarchos, Phys. Rev.B 44, 2182 (1991).

Structural and magnetic properties of Dy(Fe,V,Si)12 compounds

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Structural and magnetic properties of Dy(Fe,V,Si)12 compounds

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