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de Haas–van Alphen effect in a heavy fermion superconductor UPd2Al3
Physica B 284}288 (2000) 1291}1292
de Haas}van Alphen e!ect in a heavy fermion superconductor UPd Al
Yoshinori Haga *, Yoshihiko Inada , Kenji Sakurai, Yoshifumi Tokiwa, Etsuji Yamamoto, Tetsuo Honma, Yoshichika O nuki Advanced Science Research Center, JAERI, Tokai, Ibaraki 319-1195, Japan Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
Abstract We measured de Haas}van Alphen oscillation in UPd Al in order to reveal heavy electronic states at low temperatures down to 40 mK. For this purpose, we grew a high-quality single crystal using a puri"ed uranium metal. All the branches reported in the previous work were observed in this study. In addition, we observed a new branch f with an extremely large cyclotron mass 65m . The dHvA frequency 9.96;10 Oe for branch f coincides with the band calculations based on the itinerant 5f electron picture. 2000 Elsevier Science B.V. All rights reserved. Keywords: de Haas}von Alphen; Heavy fermion; UPd Al
The de Haas}van Alphen (dHvA) e!ect is a powerful tool in studying the heavy fermion state, because it can determine the extremal cross-sectional area, the cyclotron mass and the scattering life time of each Fermi surface [1]. Combining with band calculations, this method can determine the ground state of 5f electrons. Among the uranium-based heavy fermion systems, antiferromagnetic UPd Al is most extensively studied because it is a typical example of an exotic superconductor with an anisotropic energy gap [2]. From speci"c heat measurements, it is suggested that heavy quasiparticles with a large electronic speci"c heat coe$cient 150 mJ/K mol condense into Cooper-pairs [3]. The previous dHvA study [4] revealed a heavy cyclotron mass of 45m , m being the electron rest mass. The angular dependence of the dHvA frequency, which is proportional to the cross-sectional area of the Fermi surface, coincides well with band calculations based on the itinerant 5f electron picture [5]. Recently, we observed a new branch with a heavier mass of 65m [6], which was also predicted by band * Corresponding author. Tel.: #81-29-282-6735; fax: #8129-282-5927. E-mail address: [email protected] (Y. Haga)
calculations. The measurement in the "eld-induced ferromagnetic state above 18 T showed the heavy quasiparticles still exist although the Fermi surface was slightly modi"ed through the metamagnetic transition [7]. In this study, we present the angular dependence of the dHvA frequency. We carried out the measurement of the dHvA e!ect using a high-quality single crystal grown using a puri"ed uranium material [8]. A single crystal was grown by the Czochralski method in a tetra-arc furnace under an argon gas atmosphere. The residual resistivity ratio, which indicates the sample quality, is 104. The angular dependence of the dHvA frequency is shown in Fig. 1. New features obtained in the present study are as follows. First, the new branch f is observed only around the [0 0 0 1] direction and almost independent of the angle. This characteristic coincides with that of an inner orbit of the `party hata Fermi surface obtained by the band calculations. From the temperature dependence of the dHvA amplitude for the branch f shown in Fig. 2, the cyclotron mass along the [0 0 0 1] direction is determined to be 65m which is the heaviest in this compound. Second, the dHvA oscillation of the a branch in the hexagonal basal plane was observed. From this, it is concluded that the a branch is a closed ellipsoidal Fermi
0921-4526/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 2 5 6 6 - 1
1292
Y. Haga et al. / Physica B 284}288 (2000) 1291}1292
surface, which corresponds to the `cigara in the band calculations. Third, the e branch reported in Ref. [4] is found to split into two branches. In conclusion, we observed a heavy cyclotron mass of 65m in UPd Al . The angular dependence of the dHvA frequency coincides qualitatively with the band calculations.
References
Fig. 1. Angular dependence of the dHvA frequency of UPd Al .
Fig. 2. The temperature dependence of the dHvA amplitude. The solid curve is a "tted result, in which the cyclotron mass is determined to be 65m .
[1] Y. O nuki, A. Hasegawa, in: K.A. Gshneidner Jr., L. Eyring (Eds.), Handbook on the Physics and Chemistry of Rare Earths, Vol. 20, Elsevier, Amsterdam, 1995, p. 1. [2] H. Tou, Y. Kitaoka, K. Asayama, C. Geibel, C. Schank, F. Steglich, J. Phys. Soc. Japan 64 (1995) 725. [3] C. Geibel, C. Schank, S. Thies, H. Kitazawa, C.D. Bredl, A. BoK hm, M. Rau, A. Grauel, R. Caspary, R. Helfrich, U. Ahlheim, G. Weber, F. Steglich, Z. Phys. B 84 (1994) 1. [4] Y. Inada, A. Ishiguro, J. Kimura, N. Sato, A. Sawada, T. Komatsubara, H. Yamagami, Physica B 206&207 (1995) 33. [5] K. KnoK p#e, A. Mavromaras, L.M. Sandratskii, J. KuK bler, J. Phys.: Condens. Matter 8 (1996) 901. [6] Y. Haga, Y. Inada, K. Sakurai, Y. Tokiwa, E. Yamamoto, T. Honma, Y. O nuki, J. Phys. Soc. Japan 68 (1999) 342. [7] T. Terashima, C. Haworth, M. Takashita, H. Aoki, N. Sato, T. Komatsubara, Phys. Rev. B 55 (1997) R13 369. [8] Y. Haga, T. Honma, E. Yamamoto, H. Ohkuni, Y. O nuki, M. Ito, N. Kimura, Jpn. J. Appl. Phys. 37 (1998) 3604.
de Haas}van Alphen e!ect in a heavy fermion superconductor UPd Al
Yoshinori Haga *, Yoshihiko Inada , Kenji Sakurai, Yoshifumi Tokiwa, Etsuji Yamamoto, Tetsuo Honma, Yoshichika O nuki Advanced Science Research Center, JAERI, Tokai, Ibaraki 319-1195, Japan Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
Abstract We measured de Haas}van Alphen oscillation in UPd Al in order to reveal heavy electronic states at low temperatures down to 40 mK. For this purpose, we grew a high-quality single crystal using a puri"ed uranium metal. All the branches reported in the previous work were observed in this study. In addition, we observed a new branch f with an extremely large cyclotron mass 65m . The dHvA frequency 9.96;10 Oe for branch f coincides with the band calculations based on the itinerant 5f electron picture. 2000 Elsevier Science B.V. All rights reserved. Keywords: de Haas}von Alphen; Heavy fermion; UPd Al
The de Haas}van Alphen (dHvA) e!ect is a powerful tool in studying the heavy fermion state, because it can determine the extremal cross-sectional area, the cyclotron mass and the scattering life time of each Fermi surface [1]. Combining with band calculations, this method can determine the ground state of 5f electrons. Among the uranium-based heavy fermion systems, antiferromagnetic UPd Al is most extensively studied because it is a typical example of an exotic superconductor with an anisotropic energy gap [2]. From speci"c heat measurements, it is suggested that heavy quasiparticles with a large electronic speci"c heat coe$cient 150 mJ/K mol condense into Cooper-pairs [3]. The previous dHvA study [4] revealed a heavy cyclotron mass of 45m , m being the electron rest mass. The angular dependence of the dHvA frequency, which is proportional to the cross-sectional area of the Fermi surface, coincides well with band calculations based on the itinerant 5f electron picture [5]. Recently, we observed a new branch with a heavier mass of 65m [6], which was also predicted by band * Corresponding author. Tel.: #81-29-282-6735; fax: #8129-282-5927. E-mail address: [email protected] (Y. Haga)
calculations. The measurement in the "eld-induced ferromagnetic state above 18 T showed the heavy quasiparticles still exist although the Fermi surface was slightly modi"ed through the metamagnetic transition [7]. In this study, we present the angular dependence of the dHvA frequency. We carried out the measurement of the dHvA e!ect using a high-quality single crystal grown using a puri"ed uranium material [8]. A single crystal was grown by the Czochralski method in a tetra-arc furnace under an argon gas atmosphere. The residual resistivity ratio, which indicates the sample quality, is 104. The angular dependence of the dHvA frequency is shown in Fig. 1. New features obtained in the present study are as follows. First, the new branch f is observed only around the [0 0 0 1] direction and almost independent of the angle. This characteristic coincides with that of an inner orbit of the `party hata Fermi surface obtained by the band calculations. From the temperature dependence of the dHvA amplitude for the branch f shown in Fig. 2, the cyclotron mass along the [0 0 0 1] direction is determined to be 65m which is the heaviest in this compound. Second, the dHvA oscillation of the a branch in the hexagonal basal plane was observed. From this, it is concluded that the a branch is a closed ellipsoidal Fermi
0921-4526/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 2 5 6 6 - 1
1292
Y. Haga et al. / Physica B 284}288 (2000) 1291}1292
surface, which corresponds to the `cigara in the band calculations. Third, the e branch reported in Ref. [4] is found to split into two branches. In conclusion, we observed a heavy cyclotron mass of 65m in UPd Al . The angular dependence of the dHvA frequency coincides qualitatively with the band calculations.
References
Fig. 1. Angular dependence of the dHvA frequency of UPd Al .
Fig. 2. The temperature dependence of the dHvA amplitude. The solid curve is a "tted result, in which the cyclotron mass is determined to be 65m .
[1] Y. O nuki, A. Hasegawa, in: K.A. Gshneidner Jr., L. Eyring (Eds.), Handbook on the Physics and Chemistry of Rare Earths, Vol. 20, Elsevier, Amsterdam, 1995, p. 1. [2] H. Tou, Y. Kitaoka, K. Asayama, C. Geibel, C. Schank, F. Steglich, J. Phys. Soc. Japan 64 (1995) 725. [3] C. Geibel, C. Schank, S. Thies, H. Kitazawa, C.D. Bredl, A. BoK hm, M. Rau, A. Grauel, R. Caspary, R. Helfrich, U. Ahlheim, G. Weber, F. Steglich, Z. Phys. B 84 (1994) 1. [4] Y. Inada, A. Ishiguro, J. Kimura, N. Sato, A. Sawada, T. Komatsubara, H. Yamagami, Physica B 206&207 (1995) 33. [5] K. KnoK p#e, A. Mavromaras, L.M. Sandratskii, J. KuK bler, J. Phys.: Condens. Matter 8 (1996) 901. [6] Y. Haga, Y. Inada, K. Sakurai, Y. Tokiwa, E. Yamamoto, T. Honma, Y. O nuki, J. Phys. Soc. Japan 68 (1999) 342. [7] T. Terashima, C. Haworth, M. Takashita, H. Aoki, N. Sato, T. Komatsubara, Phys. Rev. B 55 (1997) R13 369. [8] Y. Haga, T. Honma, E. Yamamoto, H. Ohkuni, Y. O nuki, M. Ito, N. Kimura, Jpn. J. Appl. Phys. 37 (1998) 3604.