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High field magnetization and AC susceptibility studies of Ce3Rh2Ge2
ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 272–276 (2004) 79–80
High field magnetization and AC susceptibility studies of Ce3 Rh2Ge2 S. Nimoria,*, D.X. Lib a
Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan b Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan
Abstract We studied the magnetic properties in Ce3 Rh2 Ge2 polycrystalline samples using magnetization and AC susceptibility measurements. Below 7 K; where the long-range antiferromagnetic ordering occurs, the magnetization shows a metamagnetic-like jump at 3 T; and exhibits several small wriggles between 3 and 11 T: In AC susceptibility, except the sharp peak at 7 K we observed an additional small peak at 4 and 11 K in low applied fields, respectively. These behaviors indicate the complex magnetic structure of Ce3 Rh2 Ge2 at low temperatures. r 2003 Elsevier B.V. All rights reserved. PACS: 75.20.Hr; 74.70.Tx; 75.50.Ee Keywords: Kondo effect; Superconductivity; Antiferromagnetizm
Since the discovery of heavy fermion superconductivity in CeCu2 Si2 [1], many research works have been performed for the ternary compounds RET2 X2 (RE: rare earth, T: transition metal, X: metalloid). In another series of ternary intermetallic compounds RE3 T2 X2 ; recently, the superconductive behavior in La3 Rh2 Ge2 and dense Kondo behavior in Ce3 Rh2 Ge2 were observed [2]. In Ce3 Rh2 Ge2 ; the large paramagnetic Curie temperature yp of 90 K was estimated by dc susceptibility measurements, and the main future of magnetic properties corresponds to long-range antiferromagnetic ordering at 7 K [2]. However, tiny ferromagnetic components are also observable below 5 K indicating Ce3 Rh2 Ge2 is not a simple antiferromagnet in low magnetic fields. This motivated us to carry out a detailed study on the magnetic behavior of this compound by measuring the AC susceptibility in various DC fields and the high field magnetization at different temperatures. Polycrystalline sample was prepared by arc-melting. After the melting, the sample was annealed at 800 C for 2 weeks. X-ray powder diffraction shows the sample to *Corresponding author. Tel.: +81-29-863-5528; fax: +8129-863-5541. E-mail address: [email protected] (S. Nimori).
be almost single phase with orthorhombic crystal structure (Pbcm). Using a sample shaped in 3 3 3 mm3 ; the high field magnetization measurement was performed with a vibrating sample magnetometer. The vibrating frequency and amplitude was fixed to 55 Hz and 1:5 mm; respectively. In order to measure AC susceptibility we employed a SQUID magnetometer. High field magnetization curves at temperatures above TN up to 11:5 T show upper convex curvatures with monotone increasing as shown in Fig. 1. Below TN magnetization curves exhibit metamagnetic-like jumps around 3 T; which supports antiferromagnetic ordering at 7 K: Above 3 T small wriggles were observed and there are at least five local maximums up to 11:5 T: Note that the behavior of magnetizations differs between 4 and 6 K around 3 T: About this, we comment below. Fig. 2 shows temperature dependence of AC susceptibility of Ce3 Rh2 Ge2 : An antiferromagnetic peak at 7 K was confirmed for our sample in agreement with the result of Kaczorowski et al. [2]. In the present work, another peak appears in wAC curve at the temperature between 3 and 5 K in low applied fields. In addition, a rather small peak was also observed around 11 K: These two peaks disappear in high fields, meanwhile the
0304-8853/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.596
ARTICLE IN PRESS 80
S. Nimori, D.X. Li / Journal of Magnetism and Magnetic Materials 272–276 (2004) 79–80
7
Fig. 1. Magnetization curves of Ce3 Rh2 Ge2 at several temperatures.
amplitude of characteristic maximum at TN is almost independent to the applied field. But the tiny shift of TN to lower temperature was observable in high fields. The small peak around 4 K seems to be caused by reorientation of magnetic components. Magnetization processes in Fig. 1 remind us that small momentums, which are originated in canting spins or imbalance of two magnetic sublattices [3,4], align below 4 K and an antiferromagnetic ordering is completely achieved. It is considered that the small peak appeared at 11 K is also caused by remaining magnetic components. According to the specific heat measurement, no anomaly was observed around 4 and 11 K [5], which indicates that the anomalies observed in AC susceptibility are not caused by long-range magnetic ordering. The wriggles in magnetization curves in high field region and the multi-peak structure in AC susceptibility indicate that Ce3 Rh2 Ge2 is not a simple antiferromagnetic at least in low magnetic fields. It is also noticeable that the magnetic behaviors of the sample below 7 K
Fig. 2. Series of temperature dependence of the real part of ac susceptibility in several dc fields for Ce3 Rh2 Ge2 : The frequency and AC field was set to f ¼ 10 Hz and HAC ¼ 1 G; respectively.
depend on the annealing conditions and the direction of applied field, which shows evident anisotropic properties. In order to obtain further information on the complex magnetic structures of Ce3 Rh2 Ge2 ; investigations using single crystal or free-powder sample are necessary.
References [1] F. Steglich, J. Aarts, C.D. Bredl, W. Lieke, D. Meschede, W. Franz, H. Sch.afer, Phys. Rev. Lett. 43 (1979) 1892. [2] D. Kaczorowski, Yu. Prots, Yu. Grin, Phys. Rev. B 64 (2001) 224420. [3] R.E. Glandyshevskii, J.T. Zhao, E. Parth!e, Acta Crystallogr. C 48 (1992) 10. ! [4] J. Stepien-Damm, Yu. Prots, P.S. Salamakha, O.I. Bodak, J. Alloys Compounds 256 (1997) 166. [5] A. Tobo, private communication.
Journal of Magnetism and Magnetic Materials 272–276 (2004) 79–80
High field magnetization and AC susceptibility studies of Ce3 Rh2Ge2 S. Nimoria,*, D.X. Lib a
Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan b Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan
Abstract We studied the magnetic properties in Ce3 Rh2 Ge2 polycrystalline samples using magnetization and AC susceptibility measurements. Below 7 K; where the long-range antiferromagnetic ordering occurs, the magnetization shows a metamagnetic-like jump at 3 T; and exhibits several small wriggles between 3 and 11 T: In AC susceptibility, except the sharp peak at 7 K we observed an additional small peak at 4 and 11 K in low applied fields, respectively. These behaviors indicate the complex magnetic structure of Ce3 Rh2 Ge2 at low temperatures. r 2003 Elsevier B.V. All rights reserved. PACS: 75.20.Hr; 74.70.Tx; 75.50.Ee Keywords: Kondo effect; Superconductivity; Antiferromagnetizm
Since the discovery of heavy fermion superconductivity in CeCu2 Si2 [1], many research works have been performed for the ternary compounds RET2 X2 (RE: rare earth, T: transition metal, X: metalloid). In another series of ternary intermetallic compounds RE3 T2 X2 ; recently, the superconductive behavior in La3 Rh2 Ge2 and dense Kondo behavior in Ce3 Rh2 Ge2 were observed [2]. In Ce3 Rh2 Ge2 ; the large paramagnetic Curie temperature yp of 90 K was estimated by dc susceptibility measurements, and the main future of magnetic properties corresponds to long-range antiferromagnetic ordering at 7 K [2]. However, tiny ferromagnetic components are also observable below 5 K indicating Ce3 Rh2 Ge2 is not a simple antiferromagnet in low magnetic fields. This motivated us to carry out a detailed study on the magnetic behavior of this compound by measuring the AC susceptibility in various DC fields and the high field magnetization at different temperatures. Polycrystalline sample was prepared by arc-melting. After the melting, the sample was annealed at 800 C for 2 weeks. X-ray powder diffraction shows the sample to *Corresponding author. Tel.: +81-29-863-5528; fax: +8129-863-5541. E-mail address: [email protected] (S. Nimori).
be almost single phase with orthorhombic crystal structure (Pbcm). Using a sample shaped in 3 3 3 mm3 ; the high field magnetization measurement was performed with a vibrating sample magnetometer. The vibrating frequency and amplitude was fixed to 55 Hz and 1:5 mm; respectively. In order to measure AC susceptibility we employed a SQUID magnetometer. High field magnetization curves at temperatures above TN up to 11:5 T show upper convex curvatures with monotone increasing as shown in Fig. 1. Below TN magnetization curves exhibit metamagnetic-like jumps around 3 T; which supports antiferromagnetic ordering at 7 K: Above 3 T small wriggles were observed and there are at least five local maximums up to 11:5 T: Note that the behavior of magnetizations differs between 4 and 6 K around 3 T: About this, we comment below. Fig. 2 shows temperature dependence of AC susceptibility of Ce3 Rh2 Ge2 : An antiferromagnetic peak at 7 K was confirmed for our sample in agreement with the result of Kaczorowski et al. [2]. In the present work, another peak appears in wAC curve at the temperature between 3 and 5 K in low applied fields. In addition, a rather small peak was also observed around 11 K: These two peaks disappear in high fields, meanwhile the
0304-8853/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.596
ARTICLE IN PRESS 80
S. Nimori, D.X. Li / Journal of Magnetism and Magnetic Materials 272–276 (2004) 79–80
7
Fig. 1. Magnetization curves of Ce3 Rh2 Ge2 at several temperatures.
amplitude of characteristic maximum at TN is almost independent to the applied field. But the tiny shift of TN to lower temperature was observable in high fields. The small peak around 4 K seems to be caused by reorientation of magnetic components. Magnetization processes in Fig. 1 remind us that small momentums, which are originated in canting spins or imbalance of two magnetic sublattices [3,4], align below 4 K and an antiferromagnetic ordering is completely achieved. It is considered that the small peak appeared at 11 K is also caused by remaining magnetic components. According to the specific heat measurement, no anomaly was observed around 4 and 11 K [5], which indicates that the anomalies observed in AC susceptibility are not caused by long-range magnetic ordering. The wriggles in magnetization curves in high field region and the multi-peak structure in AC susceptibility indicate that Ce3 Rh2 Ge2 is not a simple antiferromagnetic at least in low magnetic fields. It is also noticeable that the magnetic behaviors of the sample below 7 K
Fig. 2. Series of temperature dependence of the real part of ac susceptibility in several dc fields for Ce3 Rh2 Ge2 : The frequency and AC field was set to f ¼ 10 Hz and HAC ¼ 1 G; respectively.
depend on the annealing conditions and the direction of applied field, which shows evident anisotropic properties. In order to obtain further information on the complex magnetic structures of Ce3 Rh2 Ge2 ; investigations using single crystal or free-powder sample are necessary.
References [1] F. Steglich, J. Aarts, C.D. Bredl, W. Lieke, D. Meschede, W. Franz, H. Sch.afer, Phys. Rev. Lett. 43 (1979) 1892. [2] D. Kaczorowski, Yu. Prots, Yu. Grin, Phys. Rev. B 64 (2001) 224420. [3] R.E. Glandyshevskii, J.T. Zhao, E. Parth!e, Acta Crystallogr. C 48 (1992) 10. ! [4] J. Stepien-Damm, Yu. Prots, P.S. Salamakha, O.I. Bodak, J. Alloys Compounds 256 (1997) 166. [5] A. Tobo, private communication.