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Magnetic and transport properties of CeRh2Si2 under high pressures
Physica B 259—261 (1999) 61—62
Magnetic and transport properties of CeRh Si under high pressures T. Muramatsu , S. Eda , T.C. Kobayashi *, M.I. Eremets, K. Amaya , S. Araki, R. Settai, Y. O nuki Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan Research Center for Materials Science at Extreme Conditions, KYOKUGEN, Osaka University, Toyonaka, Osaka 560-8531, Japan Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
Abstract Magnetic and transport properties have been investigated in the single crystal of CeRh Si under high pressures. We found that the magnetic susceptibility under high pressure shows a broad maximum like CeRu Si . In the present pressure range up to 13 kbar where the ordered state is suppressed, no obvious evidence of the superconducting transition is observed down to 50 mK. 1999 Elsevier Science B.V. All rights reserved. Keywords: Magnetic susceptibility; Electrical resistance; High pressure
Heavy fermion superconductivity (HFSC) has been paid much attention in terms of its non BCS behavior caused by the magnetic fluctuation. Up to now, pressure-induced HFSC of Ce-based Kondo-lattice system was reported in CeCu Ge [1,2], CeRh Si [3,9], CePd Si [4], CeNi Ge and CeIn [5]. These com pounds show antiferromagnetic order at ambient pressure. Application of pressure suppresses the magnetic order at the critical pressure P due to increase of the ! hybridization between 4f and conduction electrons and induces the HF state. The pressure-induced SC has been observed near and above P . ! CeRh Si shows antiferromagnetic long-range order (¹ "35 K) at ambient pressure [3,6,9]. The susceptibil, ity is highly anisotropic, reflecting the tetragonal crystal structure. Application of pressure to CeRh Si sup presses ¹ to 0 K at P &8 kbar and induces SC below , ! 0.4 K [3,9]. We measured the magnetic susceptibility and the electrical resistivity in single crystals of CeRh Si
* Corresponding author. Tel.: and fax: #81-6-850-6446; e-mail: [email protected].
under high pressures up to 13 kbar. We investigated the pressure dependence of the anisotropic susceptibility and the reconfirmation of the pressure-induced SC in order to study the relation between magnetic property and SC. Sample preparation and characterization of the single crystal in the present experiment was described in Ref. [6]. Pressure was provided by a piston-cylinder cell. Pressure value was decided by the SC transition temperature of a small piece of Pb in the sample chamber. Susceptibility was measured by the SQUID magnetometer. Resistance measurement was carried out by AC 4-probe method. Temperature dependence of the susceptibilities s and s of CeRh Si under high pressure is shown in Fig. 1. Applied magnetic field is 1 T along the crystal c- and a-axis for s and s . The antiferromagnetic ordering tem perature ¹ is obtained as the onset of rapid decrease of , s . The ¹ disappears at around 11 kbar as shown in , Fig. 2. It is characteristic that the broad maximum of s appears above ¹ by application of pressure. The , ¹ shifts to higher temperatures and the maximum
value decreases rapidly with increasing pressure, which is explained to be due to the increase of the c—f hybridization. This behavior is similar to the case of CeRu Si
0921-4526/99/$ — see front matter 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 8 ) 0 0 9 0 9 - 0
62
T. Muramatsu et al. / Physica B 259—261 (1999) 61—62
Fig. 1. Temperature dependence of the susceptibilities along the crystal c- and a-axis of CeRh Si under high pressures.
Fig. 2. Pressure dependence of ¹ (䉱,䉲) single crystal; (䢇)poly, crystal) and ¹ (䉭) where the s shows the broad maximum.
which shows a maximum of s and metamagnetic mag netization process in the field parallel to the c-axis. In CeRh Si , the metamagnetic magnetization may be ex pected and the experiment of high-field magnetization process under high pressure is now in progress [7]. On the other hand, the s decreases slightly and also shows the broad maximum under high pressure. Application of pressure reduces the magnetic anisotropy as s /s "5.6 (ambient pressure) and 3.8 (&P ) which are estimated ! from the maximum value of s and s . Electrical resistance measurement was carried out in order to confirm the pressure-induced SC reported previously [3,9]. We examined three single crystals and two polycrystals. The single crystals are (1) as-grown sample and (2) annealed samples made of different starting materials of Ce having purity of 3N and 4N. The typical result of a single crystal is shown in Fig. 3. For all the samples, we could not observe an obvious sign of the SC at around P down to 50 mK. In only one of the poly!
Fig. 3. Electrical resistance in a single crystal of CeRh Si at 13 kbar. There is no evidence of the pressure-induced superconductivity.
crystals, we observed the small resistance drop (&7%) below 0.4 K under the pressure of 13 kbar [8]. Since the applied field of 0.3 T suppresses this resistance drop, we consider that partial SC causes this drop. In all of the samples, the temperature dependence of the resistance is similar to the previous result which follows ¹-dependence of Fermi liquid behavior at low-temperature region. In conclusion, we found a maximum of the susceptibility under high pressures, while no obvious evidence of SC was obtained. These are similar to the results in CeRu Si . The magnetic anisotropy may be responsible for the absence of the pressure-induced SC.
This work has been supported by CREST (Core Research for Evolutional Science and Technology) of Japan Science and Technology Corporation (JST), the COE Research (10CE2004) in Grant-in-Aid for Scientific Research from the Ministry of Education, Sport, Science and Culture in Japan.
References [1] [2] [3] [4] [5] [6] [7]
D. Jaccard et al., Physica B 230—232 (1997) 297. T.C. Kobayashi et al., J. Phys. Soc. Japan 67 (1998) 996. R. Movshovich et al., Physica B 223 and 224 (1996) 126. F.M. Grosche et al., Physica B 223 and 224 (1996) 50. I.R. Walker et al., Physica C 282—287 (1997) 303. R. Settai et al., J. Phys. Soc. Japan 66 (1997) 2260. T. Hamamoto et al., Proc. PPHMFIII, FL, 1998, to be submitted. [8] K. Ishida et al., unpublished. [9] R. Movshovich et al., Phys. Rev. B 53 (1996) 8241.
Magnetic and transport properties of CeRh Si under high pressures T. Muramatsu , S. Eda , T.C. Kobayashi *, M.I. Eremets, K. Amaya , S. Araki, R. Settai, Y. O nuki Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan Research Center for Materials Science at Extreme Conditions, KYOKUGEN, Osaka University, Toyonaka, Osaka 560-8531, Japan Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
Abstract Magnetic and transport properties have been investigated in the single crystal of CeRh Si under high pressures. We found that the magnetic susceptibility under high pressure shows a broad maximum like CeRu Si . In the present pressure range up to 13 kbar where the ordered state is suppressed, no obvious evidence of the superconducting transition is observed down to 50 mK. 1999 Elsevier Science B.V. All rights reserved. Keywords: Magnetic susceptibility; Electrical resistance; High pressure
Heavy fermion superconductivity (HFSC) has been paid much attention in terms of its non BCS behavior caused by the magnetic fluctuation. Up to now, pressure-induced HFSC of Ce-based Kondo-lattice system was reported in CeCu Ge [1,2], CeRh Si [3,9], CePd Si [4], CeNi Ge and CeIn [5]. These com pounds show antiferromagnetic order at ambient pressure. Application of pressure suppresses the magnetic order at the critical pressure P due to increase of the ! hybridization between 4f and conduction electrons and induces the HF state. The pressure-induced SC has been observed near and above P . ! CeRh Si shows antiferromagnetic long-range order (¹ "35 K) at ambient pressure [3,6,9]. The susceptibil, ity is highly anisotropic, reflecting the tetragonal crystal structure. Application of pressure to CeRh Si sup presses ¹ to 0 K at P &8 kbar and induces SC below , ! 0.4 K [3,9]. We measured the magnetic susceptibility and the electrical resistivity in single crystals of CeRh Si
* Corresponding author. Tel.: and fax: #81-6-850-6446; e-mail: [email protected].
under high pressures up to 13 kbar. We investigated the pressure dependence of the anisotropic susceptibility and the reconfirmation of the pressure-induced SC in order to study the relation between magnetic property and SC. Sample preparation and characterization of the single crystal in the present experiment was described in Ref. [6]. Pressure was provided by a piston-cylinder cell. Pressure value was decided by the SC transition temperature of a small piece of Pb in the sample chamber. Susceptibility was measured by the SQUID magnetometer. Resistance measurement was carried out by AC 4-probe method. Temperature dependence of the susceptibilities s and s of CeRh Si under high pressure is shown in Fig. 1. Applied magnetic field is 1 T along the crystal c- and a-axis for s and s . The antiferromagnetic ordering tem perature ¹ is obtained as the onset of rapid decrease of , s . The ¹ disappears at around 11 kbar as shown in , Fig. 2. It is characteristic that the broad maximum of s appears above ¹ by application of pressure. The , ¹ shifts to higher temperatures and the maximum
value decreases rapidly with increasing pressure, which is explained to be due to the increase of the c—f hybridization. This behavior is similar to the case of CeRu Si
0921-4526/99/$ — see front matter 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 8 ) 0 0 9 0 9 - 0
62
T. Muramatsu et al. / Physica B 259—261 (1999) 61—62
Fig. 1. Temperature dependence of the susceptibilities along the crystal c- and a-axis of CeRh Si under high pressures.
Fig. 2. Pressure dependence of ¹ (䉱,䉲) single crystal; (䢇)poly, crystal) and ¹ (䉭) where the s shows the broad maximum.
which shows a maximum of s and metamagnetic mag netization process in the field parallel to the c-axis. In CeRh Si , the metamagnetic magnetization may be ex pected and the experiment of high-field magnetization process under high pressure is now in progress [7]. On the other hand, the s decreases slightly and also shows the broad maximum under high pressure. Application of pressure reduces the magnetic anisotropy as s /s "5.6 (ambient pressure) and 3.8 (&P ) which are estimated ! from the maximum value of s and s . Electrical resistance measurement was carried out in order to confirm the pressure-induced SC reported previously [3,9]. We examined three single crystals and two polycrystals. The single crystals are (1) as-grown sample and (2) annealed samples made of different starting materials of Ce having purity of 3N and 4N. The typical result of a single crystal is shown in Fig. 3. For all the samples, we could not observe an obvious sign of the SC at around P down to 50 mK. In only one of the poly!
Fig. 3. Electrical resistance in a single crystal of CeRh Si at 13 kbar. There is no evidence of the pressure-induced superconductivity.
crystals, we observed the small resistance drop (&7%) below 0.4 K under the pressure of 13 kbar [8]. Since the applied field of 0.3 T suppresses this resistance drop, we consider that partial SC causes this drop. In all of the samples, the temperature dependence of the resistance is similar to the previous result which follows ¹-dependence of Fermi liquid behavior at low-temperature region. In conclusion, we found a maximum of the susceptibility under high pressures, while no obvious evidence of SC was obtained. These are similar to the results in CeRu Si . The magnetic anisotropy may be responsible for the absence of the pressure-induced SC.
This work has been supported by CREST (Core Research for Evolutional Science and Technology) of Japan Science and Technology Corporation (JST), the COE Research (10CE2004) in Grant-in-Aid for Scientific Research from the Ministry of Education, Sport, Science and Culture in Japan.
References [1] [2] [3] [4] [5] [6] [7]
D. Jaccard et al., Physica B 230—232 (1997) 297. T.C. Kobayashi et al., J. Phys. Soc. Japan 67 (1998) 996. R. Movshovich et al., Physica B 223 and 224 (1996) 126. F.M. Grosche et al., Physica B 223 and 224 (1996) 50. I.R. Walker et al., Physica C 282—287 (1997) 303. R. Settai et al., J. Phys. Soc. Japan 66 (1997) 2260. T. Hamamoto et al., Proc. PPHMFIII, FL, 1998, to be submitted. [8] K. Ishida et al., unpublished. [9] R. Movshovich et al., Phys. Rev. B 53 (1996) 8241.