- Email: [email protected]
Susceptibility measurements of R2CuIn3 compounds (R=Ce, Pr, Nd, Tb, Dy, Ho, Er)
L
Journal of Alloys and Compounds 297 (2000) 26–29
www.elsevier.com / locate / jallcom
Susceptibility measurements of R 2 CuIn 3 compounds (R5Ce, Pr, Nd, Tb, Dy, Ho, Er) I.M. Siouris *,1 , I.P. Semitelou, J.K. Yakinthos Democritus University of Thrace, Electrical and Computer Engineering Department, Physics Laboratory, 67100 Xanthi, Greece Received 21 June 1999; accepted 19 August 1999
Abstract R 2 CuIn 3 (R5Ce, Pr, Nd, Tb, Dy, Ho, Er) compounds crystallize in the hexagonal P63 /mmm space group. Susceptibility measurements, showed that compounds with R5Nd, Tb, Dy, Ho and Er order antiferromagnetically with T N ranging from 8 K (Ho) to 30 K (Tb). Ce 2 CuIn 3 and Pr 2 CuIn 3 do not show any ordering temperature down to 4.2 K. The compounds with R5Tb, Er present two magnetic phase transitions. 2000 Elsevier Science S.A. All rights reserved. Keywords: Rare-earth; Indium; Copper; Magnetic ordering; Magnetization process
1. Introduction The physical properties of intermetallic rare earth–indium compounds have been extensively studied. Ternary indides may be synthesized from rare earths with silver and indium. The latter two elements form a statistical mixture in R 2 AgIn 3 [1], known to crystallize in the hexagonal CaIn 2 -type structure and are currently under investigation in our laboratory. These compounds give rise to a spin glass like behavior or to commensurate antiferromagnetic structures [2,3]. However, a particularly interesting class of compounds arises, by the total substitution of Ni or Cu for Ag, which crystallize in the AlB 2 -type
structure in the P63 /mmm space group as reported in [4,5]. Our present work is focused on the macroscopic magnetic properties of the R 2 CuIn 3 compound.
2. Experimental The samples were prepared by arc-melting a stoichiometric mixture of high purity elements pressed in pellets under a helium atmosphere. To ensure homogeneity the alloys were annealed for 30 days at 750 K. X-ray analysis showed that all samples reported were single phase. The lattice parameters, presented in Table 1, were determined
Table 1 Main crystallographic and magnetic characteristics of the R 2 CuIn 3 compound
Ce 2 CuIn 3 Pr 2 CuIn 3 Nd 2 CuIn 3 Tb 2 CuIn 3 Dy 2 CuIn 3 Ho 2 CuIn 3 Er 2 CuIn 3 a
˚ a(A)
˚ c(A)
T N (K)
up( Obs)
meff
4.821 4.808 4.821 4.702 4.739 4.690 4.678
3.852 3.860 3.809 3.642 3.635 3.627 3.625
– – 12 30 22 8 9
28 23 212 272 230 2 223
2.49 3.48 3.75 10.3 10.5 10.47 10.55
meff( Exp.) , meff( Theor.) in ( mB ); up( Obs) in (K).
*Corresponding author. 1 This article is a part of his thesis. 0925-8388 / 00 / $ – see front matter 2000 Elsevier Science S.A. All rights reserved. PII: S0925-8388( 99 )00566-6
( Exp.)
meff
a ( Theor.)
2.54 3.58 3.68 9.72 10.65 10.6 9.58
I.M. Siouris et al. / Journal of Alloys and Compounds 297 (2000) 26 – 29
Fig. 1. Temperature dependence of the reciprocal susceptibility of two R 2 CuIn 3 compounds.
on the basis of the hexagonal P63 /mmm space group using the program POWLS [6]. Susceptibility measurements at temperatures ranging from 4.2 K to 160 K, under constant applied magnetic field of 1 kOe, were realized by means of a SQUID magnetometer.
27
Fig. 2. Values of observed paramagnetic Curie temperature, up , for R 2 CuIn 3 compounds as compared to the De Gennes factor.
3. Results and conclusion
3.1. High temperature susceptibility The reciprocal susceptibility 1 /x vs. temperature T
Fig. 3. Reciprocal susceptibility vs. temperature curve, under 1 kOe, of Nd 2 CuIn 3 . Inset: susceptibility vs. temperature curve.
28
I.M. Siouris et al. / Journal of Alloys and Compounds 297 (2000) 26 – 29
Fig. 4. Reciprocal susceptibility vs. temperature curves, under 1 kOe, of Dy 2 CuIn 3 and Ho 2 CuIn 3 . Inset: susceptibility vs. temperature curves.
curves of the R 2 CuIn 3 compounds follow a Curie–Weiss law above 50 K (Figs. 1, 3, 4,5). All compounds present negative paramagnetic Curie temperatures (PCT), up , with the exception of Ho 2 CuIn 3 , for which up is positive. Fig. 2
shows that the up values of the heavy rare earth compounds do not follow the De Gennes law up ¯( gj 21)2 J(J11) [7], ( gj 5Lande´ factor, J5total angular momentum), based on the RKKY theory. Consequently, the magnetic interactions
Fig. 5. Reciprocal susceptibility vs. temperature curves, measured in 1 kOe, of Tb 2 CuIn 3 and Er 2 CuIn 3 . Inset: susceptibility vs. temperature curves.
I.M. Siouris et al. / Journal of Alloys and Compounds 297 (2000) 26 – 29
of these compounds must be more complex. The effective magnetic moment, meff , deduced from the high temperature susceptibility data, is found to be nearly the same as the free ion value for the compounds with R5Ce, Pr, Nd, Dy and Ho. For the compounds with R5Tb and Er, the meff value is higher than the free ion value. The same deviation was observed for Tb 2 AgIn 3 [3]. This discrepancy may be due to a contribution of the conduction electrons to the magnetic moments [7]. In the temperature range 30–40 K, a slight change in the susceptibility slope for the compounds with terbium and erbium is present, probably indicating a phase transition.
29
experiments are in process to investigate the magnetic structure of the R 2 CuIn 3 compounds.
Acknowledgements Thanks are due to Dr. J.K. Regnault director of MDN / D.R.F. du Centre d’Etudes Nucleaires de Grenoble, for the hospitality received by Professor J.K. Yakinthos in his laboratory, as well as to Mr J.F. Jacquot for technical assistance.
3.2. Low temperature susceptibility References Ce 2 CuIn 3 and Pr 2 CuIn 3 do not show any magnetic ordering and remain paramagnetic down to 4.2 K (Fig. 1). For the rest of the R 2 CuIn 3 compounds, the susceptibility curves show maxima, revealing antiferromagnetic behavior (Figs. 3, 4, 5). The compounds Tb 2 CuIn 3 and Er 2 CuIn 3 show except maxima, extra minima at around 30 and 9 K, respectively (Fig. 3). This is an indication of the presence of a second magnetic phase. The lattice parameters (a, c), ´ temthe paramagnetic Curie temperatures (up ), the Neel peratures (T N ) and the experimental and theoretical effective magnetic moments ( meff ) of the R 2 CuIn 3 compounds are reported in Table 1. Currently neutron diffraction
[1] L.V. Sysa, Y.M. Kalychak, Izvestiya Akademii Nauk SSSR, Metally 3 (1997) 126–129. [2] J.M. Siouris, J.P. Semitelou, J.K. Yakinthos, D. Schmitt. The 6th EPDIC Budapest, Aug. 1998 [3] J.P. Semitelou, J.M. Siouris, J.K. Yakinthos, W. Schafer, D. Schmitt, J. Alloys Comp. 283 (1999) 12–15. [4] V.M. Baranyak, O.V. Dmytrakh, Ya.M. Kalychak, P.Yu. Zavalii, Izvestiya Akademii Nauk SSSR, Neorganicheskie materialy 24 (5) (1988) 739–740. [5] Ya.M. Kalychak, J. Alloys Comp. 262–263 (1997) 341–345. [6] G. Will, POWLS: ‘A powder least squares program’, J. Appl. Crystallogr. 12 (1979) 483–485. [7] P.G. De Gennes, J. Phys. Radium 23 (1962) 510.
Journal of Alloys and Compounds 297 (2000) 26–29
www.elsevier.com / locate / jallcom
Susceptibility measurements of R 2 CuIn 3 compounds (R5Ce, Pr, Nd, Tb, Dy, Ho, Er) I.M. Siouris *,1 , I.P. Semitelou, J.K. Yakinthos Democritus University of Thrace, Electrical and Computer Engineering Department, Physics Laboratory, 67100 Xanthi, Greece Received 21 June 1999; accepted 19 August 1999
Abstract R 2 CuIn 3 (R5Ce, Pr, Nd, Tb, Dy, Ho, Er) compounds crystallize in the hexagonal P63 /mmm space group. Susceptibility measurements, showed that compounds with R5Nd, Tb, Dy, Ho and Er order antiferromagnetically with T N ranging from 8 K (Ho) to 30 K (Tb). Ce 2 CuIn 3 and Pr 2 CuIn 3 do not show any ordering temperature down to 4.2 K. The compounds with R5Tb, Er present two magnetic phase transitions. 2000 Elsevier Science S.A. All rights reserved. Keywords: Rare-earth; Indium; Copper; Magnetic ordering; Magnetization process
1. Introduction The physical properties of intermetallic rare earth–indium compounds have been extensively studied. Ternary indides may be synthesized from rare earths with silver and indium. The latter two elements form a statistical mixture in R 2 AgIn 3 [1], known to crystallize in the hexagonal CaIn 2 -type structure and are currently under investigation in our laboratory. These compounds give rise to a spin glass like behavior or to commensurate antiferromagnetic structures [2,3]. However, a particularly interesting class of compounds arises, by the total substitution of Ni or Cu for Ag, which crystallize in the AlB 2 -type
structure in the P63 /mmm space group as reported in [4,5]. Our present work is focused on the macroscopic magnetic properties of the R 2 CuIn 3 compound.
2. Experimental The samples were prepared by arc-melting a stoichiometric mixture of high purity elements pressed in pellets under a helium atmosphere. To ensure homogeneity the alloys were annealed for 30 days at 750 K. X-ray analysis showed that all samples reported were single phase. The lattice parameters, presented in Table 1, were determined
Table 1 Main crystallographic and magnetic characteristics of the R 2 CuIn 3 compound
Ce 2 CuIn 3 Pr 2 CuIn 3 Nd 2 CuIn 3 Tb 2 CuIn 3 Dy 2 CuIn 3 Ho 2 CuIn 3 Er 2 CuIn 3 a
˚ a(A)
˚ c(A)
T N (K)
up( Obs)
meff
4.821 4.808 4.821 4.702 4.739 4.690 4.678
3.852 3.860 3.809 3.642 3.635 3.627 3.625
– – 12 30 22 8 9
28 23 212 272 230 2 223
2.49 3.48 3.75 10.3 10.5 10.47 10.55
meff( Exp.) , meff( Theor.) in ( mB ); up( Obs) in (K).
*Corresponding author. 1 This article is a part of his thesis. 0925-8388 / 00 / $ – see front matter 2000 Elsevier Science S.A. All rights reserved. PII: S0925-8388( 99 )00566-6
( Exp.)
meff
a ( Theor.)
2.54 3.58 3.68 9.72 10.65 10.6 9.58
I.M. Siouris et al. / Journal of Alloys and Compounds 297 (2000) 26 – 29
Fig. 1. Temperature dependence of the reciprocal susceptibility of two R 2 CuIn 3 compounds.
on the basis of the hexagonal P63 /mmm space group using the program POWLS [6]. Susceptibility measurements at temperatures ranging from 4.2 K to 160 K, under constant applied magnetic field of 1 kOe, were realized by means of a SQUID magnetometer.
27
Fig. 2. Values of observed paramagnetic Curie temperature, up , for R 2 CuIn 3 compounds as compared to the De Gennes factor.
3. Results and conclusion
3.1. High temperature susceptibility The reciprocal susceptibility 1 /x vs. temperature T
Fig. 3. Reciprocal susceptibility vs. temperature curve, under 1 kOe, of Nd 2 CuIn 3 . Inset: susceptibility vs. temperature curve.
28
I.M. Siouris et al. / Journal of Alloys and Compounds 297 (2000) 26 – 29
Fig. 4. Reciprocal susceptibility vs. temperature curves, under 1 kOe, of Dy 2 CuIn 3 and Ho 2 CuIn 3 . Inset: susceptibility vs. temperature curves.
curves of the R 2 CuIn 3 compounds follow a Curie–Weiss law above 50 K (Figs. 1, 3, 4,5). All compounds present negative paramagnetic Curie temperatures (PCT), up , with the exception of Ho 2 CuIn 3 , for which up is positive. Fig. 2
shows that the up values of the heavy rare earth compounds do not follow the De Gennes law up ¯( gj 21)2 J(J11) [7], ( gj 5Lande´ factor, J5total angular momentum), based on the RKKY theory. Consequently, the magnetic interactions
Fig. 5. Reciprocal susceptibility vs. temperature curves, measured in 1 kOe, of Tb 2 CuIn 3 and Er 2 CuIn 3 . Inset: susceptibility vs. temperature curves.
I.M. Siouris et al. / Journal of Alloys and Compounds 297 (2000) 26 – 29
of these compounds must be more complex. The effective magnetic moment, meff , deduced from the high temperature susceptibility data, is found to be nearly the same as the free ion value for the compounds with R5Ce, Pr, Nd, Dy and Ho. For the compounds with R5Tb and Er, the meff value is higher than the free ion value. The same deviation was observed for Tb 2 AgIn 3 [3]. This discrepancy may be due to a contribution of the conduction electrons to the magnetic moments [7]. In the temperature range 30–40 K, a slight change in the susceptibility slope for the compounds with terbium and erbium is present, probably indicating a phase transition.
29
experiments are in process to investigate the magnetic structure of the R 2 CuIn 3 compounds.
Acknowledgements Thanks are due to Dr. J.K. Regnault director of MDN / D.R.F. du Centre d’Etudes Nucleaires de Grenoble, for the hospitality received by Professor J.K. Yakinthos in his laboratory, as well as to Mr J.F. Jacquot for technical assistance.
3.2. Low temperature susceptibility References Ce 2 CuIn 3 and Pr 2 CuIn 3 do not show any magnetic ordering and remain paramagnetic down to 4.2 K (Fig. 1). For the rest of the R 2 CuIn 3 compounds, the susceptibility curves show maxima, revealing antiferromagnetic behavior (Figs. 3, 4, 5). The compounds Tb 2 CuIn 3 and Er 2 CuIn 3 show except maxima, extra minima at around 30 and 9 K, respectively (Fig. 3). This is an indication of the presence of a second magnetic phase. The lattice parameters (a, c), ´ temthe paramagnetic Curie temperatures (up ), the Neel peratures (T N ) and the experimental and theoretical effective magnetic moments ( meff ) of the R 2 CuIn 3 compounds are reported in Table 1. Currently neutron diffraction
[1] L.V. Sysa, Y.M. Kalychak, Izvestiya Akademii Nauk SSSR, Metally 3 (1997) 126–129. [2] J.M. Siouris, J.P. Semitelou, J.K. Yakinthos, D. Schmitt. The 6th EPDIC Budapest, Aug. 1998 [3] J.P. Semitelou, J.M. Siouris, J.K. Yakinthos, W. Schafer, D. Schmitt, J. Alloys Comp. 283 (1999) 12–15. [4] V.M. Baranyak, O.V. Dmytrakh, Ya.M. Kalychak, P.Yu. Zavalii, Izvestiya Akademii Nauk SSSR, Neorganicheskie materialy 24 (5) (1988) 739–740. [5] Ya.M. Kalychak, J. Alloys Comp. 262–263 (1997) 341–345. [6] G. Will, POWLS: ‘A powder least squares program’, J. Appl. Crystallogr. 12 (1979) 483–485. [7] P.G. De Gennes, J. Phys. Radium 23 (1962) 510.