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de Haas–van Alphen effect in LaRu4P12
Physica B 328 (2003) 68–70
de Haas–van Alphen effect in LaRu4P12 S.R. Sahaa,*, H. Sugawaraa, R. Sakaia, Y. Aokia, H. Satoa, Y. Inadab, b,c % H. Shishidob, R. Settaib, Y. Onuki , H. Harimad a
Department of Physics, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan b Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan c ASRC, Japan Atomic Energy Research Institute, Tokai, Ibaraki, Japan d ISIR, Osaka University, Ibaraki, Osaka 567-0047, Japan
Abstract We report the first successful observation of the de Haas–van Alphen effect in the filled skutterudite LaRu4 P12 : Observed Fermi surfaces (FSs) are close to those expected from the band calculation. The effective mass mnc is roughly twice compared to the calculated band mass. Assuming the similarity of FS between LaRu4 P12 and PrRu4 P12 ; the FS nesting with q ¼ ð1; 0; 0Þ as a possible origin of the M–I transition in PrRu4 P12 is discussed. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Metal–insulator transition; de Haas–van Alphen effect; Filled skutterudite; LaRu4 P12 ; PrRu4 P12
The filled-skutterudite compounds RETr4 Pn12 (RE ¼ rare earth, Tr ¼ Fe; Ru, Os, and Pn ¼ pnictogen) have attracted much attention from the view points of both novel physical properties, i.e., metal–insulator (M–I) transition, superconductivity, semiconducting transport property, magnetic ordering, and their thermoelectric applications [1–4]. Among Pr-based compounds, PrFe4 P12 shows an anomalous nonmagnetic phase transition at TA ¼ 6:5 K and a heavy cyclotron mass B80m0 indicating the presence of strong correlation of conduction electrons [3]. PrRu4 P12 shows an M–I transition at TMI ¼ 60 K [1]. Although several studies have been carried out [1,5,6], the origin of the M–I transition still remains controversial.
*Corresponding author. Tel.: +81-426-77-2487; fax: +81426-77-2483. E-mail address: [email protected] (S.R. Saha).
From the band-structure calculation, the origin of M–I transition is suggested as the nesting of the FS with q ¼ ð1; 0; 0Þ: However, experimental FS is not yet clarified. Although the M–I transition in PrRu4 P12 prevents the observation of dHvA oscillations at low temperatures, understanding of the Fermi surface in the reference compound LaRu4 P12 can provide information on PrRu4 P12 if the 4f electrons of Pr are localized. We have succeeded to grow a high quality single crystal of LaRu4 P12 : In this proceedings, we report preliminary results of the first successful de Haas–van Alphen (dHvA) experiments on LaRu4 P12 : Single crystals of LaRu4 P12 were grown by the tin-flux method which is basically the same as described in Ref. [7]. The raw materials were 4N (99.99% pure)-La, -Ru, 6N-P, and 5N-Sn. The residual resistivity ratio (RRR) of the present sample is B1000; indicating high quality of the sample. The dHvA experiments were performed in a 15 T superconducting magnet with a
0921-4526/03/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0921-4526(02)01811-2
S.R. Saha et al. / Physica B 328 (2003) 68–70 3
He-cryostat down to 0:4 K: The dHvA signals were detected by means of the conventional field modulation method. Fig. 1 shows (a) a typical recorder trace of the dHvA oscillations and (b) the corresponding fast Fourier transformation (FFT) spectrum in LaRu4 P12 at 0:4 K: There is at least one fundamental dHvA branch a above the superconducting upper critical field HC2 of LaRu4 P12 : The frequency of a branch is 5:8 107 Oe; which is close to the value obtained from the band calculation given in Table 1. From the temperature dependence of the dHvA amplitude A; we can estimate the cyclotron effective mass mnc as shown in Fig. 2 and the determined value for a branch is given with the
69
calculated one in Table 1. The effective mass mnc in the experiment is enhanced roughly twice compared with the calculated one, which is anomalous and should be related with the electron–electron and/or electron–phonon interactions. The angular dependences of dHvA branches (detail will be given in Ref. [8]) are close to the calculated 48th band FS [6] that is like a distorted cube and the volume is nearly a half of the first Brillouin zone. Assuming the similar Fermi surface in PrRu4 P12 [6], the nesting of the Fermi surface with q ¼ ð1; 0; 0Þ could be an origin of the M–I transition in PrRu4 P12 ; though the scenario remains an unsolved issue why LaRu4 P12 does not show any M–I transition. The band calculation shows there exist other Fermi surfaces [6] which would suppress any nesting in LaRu4 P12 :
H || <100> 0.44K
Table 1 The dHvA frequencies F and the cyclotron effective masses mnc along /1 0 0S in LaRu4 P12 Experiment
90kOe
1/H
Branch
F ð107 OeÞ
mnc =m0
F ð107 OeÞ
mnc =m0
a
5.8
2.9
5.5
1.8
ln{A[1-exp(-2λm*CT/H)]/ T} (arb. units)
120kOe
α
mC* = 2.93 ± 0.01m0
LaRu4P12 α = 5.8 x 107 Oe H || <100>
0.4
0
2
4
6
8
10
12
dHvA Frequency (107 Oe) Fig. 1. (a) The typical dHvA oscillations and (b) its fast Fourier transformation (FFT) spectrum in LaRu4 P12 :
Calculation
0.5
0.6
0.7
0.8
0.9
1.0
1.1
T (K) Fig. 2. The semi-logarithmic plot of the reduced dHvA amplitude A vs. temperature for a-branch in LaRu4 P12 : l in the vertical-axis label is a constant l ¼ 2p2 ckB =e_: The mnc was estimated at around 110 kOe:
70
S.R. Saha et al. / Physica B 328 (2003) 68–70
However, in order to detect those Fermi surfaces measurements should be extended to temperatures lower than 0:4 K:
Acknowledgements One of the authors (S.R. Saha) acknowledges the support of a fellowship from Japan Society for the Promotion of Science. This work has also been partly supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Science, Sports, and Technology of Japan.
References [1] C. Sekine, et al., Phys. Rev. Lett. 79 (1997) 3218; C. Sekine, et al., Physica B 281& 282 (2000) 303; C. Sekine, et al., Physica B 281& 282 (2000) 300. [2] H. Sato, et al., Phys. Rev. B 62 (2000) 15125; Y. Aoki, et al., Phys. Rev. B 65 (2002) 064446. [3] H. Sugawara, et al., J. Phys. Soc. Japan 69 (2000) 2938; H. Sugawara, et al., Phys. Rev. B 66 (2002) 134411. [4] I. Shirotani, et al., Phys. Rev. B 56 (1997) 7866. [5] C.H. Lee, et al., Phys. Rev. B 60 (1999) 13253; C.H. Lee, et al., J. Phys.: Condens. Matter 13 (2001) L45–48. [6] H. Harima, et al., Prog. Theor. Phys. Suppl. 138 (2000) 117; H. Harima, et al., Physica B 312–313 (2002) 843. [7] M.S. Torikachvili, et al., Phys. Rev. B 36 (1987) 8660. [8] S.R. Saha, et al. (in preparation).
de Haas–van Alphen effect in LaRu4P12 S.R. Sahaa,*, H. Sugawaraa, R. Sakaia, Y. Aokia, H. Satoa, Y. Inadab, b,c % H. Shishidob, R. Settaib, Y. Onuki , H. Harimad a
Department of Physics, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan b Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan c ASRC, Japan Atomic Energy Research Institute, Tokai, Ibaraki, Japan d ISIR, Osaka University, Ibaraki, Osaka 567-0047, Japan
Abstract We report the first successful observation of the de Haas–van Alphen effect in the filled skutterudite LaRu4 P12 : Observed Fermi surfaces (FSs) are close to those expected from the band calculation. The effective mass mnc is roughly twice compared to the calculated band mass. Assuming the similarity of FS between LaRu4 P12 and PrRu4 P12 ; the FS nesting with q ¼ ð1; 0; 0Þ as a possible origin of the M–I transition in PrRu4 P12 is discussed. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Metal–insulator transition; de Haas–van Alphen effect; Filled skutterudite; LaRu4 P12 ; PrRu4 P12
The filled-skutterudite compounds RETr4 Pn12 (RE ¼ rare earth, Tr ¼ Fe; Ru, Os, and Pn ¼ pnictogen) have attracted much attention from the view points of both novel physical properties, i.e., metal–insulator (M–I) transition, superconductivity, semiconducting transport property, magnetic ordering, and their thermoelectric applications [1–4]. Among Pr-based compounds, PrFe4 P12 shows an anomalous nonmagnetic phase transition at TA ¼ 6:5 K and a heavy cyclotron mass B80m0 indicating the presence of strong correlation of conduction electrons [3]. PrRu4 P12 shows an M–I transition at TMI ¼ 60 K [1]. Although several studies have been carried out [1,5,6], the origin of the M–I transition still remains controversial.
*Corresponding author. Tel.: +81-426-77-2487; fax: +81426-77-2483. E-mail address: [email protected] (S.R. Saha).
From the band-structure calculation, the origin of M–I transition is suggested as the nesting of the FS with q ¼ ð1; 0; 0Þ: However, experimental FS is not yet clarified. Although the M–I transition in PrRu4 P12 prevents the observation of dHvA oscillations at low temperatures, understanding of the Fermi surface in the reference compound LaRu4 P12 can provide information on PrRu4 P12 if the 4f electrons of Pr are localized. We have succeeded to grow a high quality single crystal of LaRu4 P12 : In this proceedings, we report preliminary results of the first successful de Haas–van Alphen (dHvA) experiments on LaRu4 P12 : Single crystals of LaRu4 P12 were grown by the tin-flux method which is basically the same as described in Ref. [7]. The raw materials were 4N (99.99% pure)-La, -Ru, 6N-P, and 5N-Sn. The residual resistivity ratio (RRR) of the present sample is B1000; indicating high quality of the sample. The dHvA experiments were performed in a 15 T superconducting magnet with a
0921-4526/03/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0921-4526(02)01811-2
S.R. Saha et al. / Physica B 328 (2003) 68–70 3
He-cryostat down to 0:4 K: The dHvA signals were detected by means of the conventional field modulation method. Fig. 1 shows (a) a typical recorder trace of the dHvA oscillations and (b) the corresponding fast Fourier transformation (FFT) spectrum in LaRu4 P12 at 0:4 K: There is at least one fundamental dHvA branch a above the superconducting upper critical field HC2 of LaRu4 P12 : The frequency of a branch is 5:8 107 Oe; which is close to the value obtained from the band calculation given in Table 1. From the temperature dependence of the dHvA amplitude A; we can estimate the cyclotron effective mass mnc as shown in Fig. 2 and the determined value for a branch is given with the
69
calculated one in Table 1. The effective mass mnc in the experiment is enhanced roughly twice compared with the calculated one, which is anomalous and should be related with the electron–electron and/or electron–phonon interactions. The angular dependences of dHvA branches (detail will be given in Ref. [8]) are close to the calculated 48th band FS [6] that is like a distorted cube and the volume is nearly a half of the first Brillouin zone. Assuming the similar Fermi surface in PrRu4 P12 [6], the nesting of the Fermi surface with q ¼ ð1; 0; 0Þ could be an origin of the M–I transition in PrRu4 P12 ; though the scenario remains an unsolved issue why LaRu4 P12 does not show any M–I transition. The band calculation shows there exist other Fermi surfaces [6] which would suppress any nesting in LaRu4 P12 :
H || <100> 0.44K
Table 1 The dHvA frequencies F and the cyclotron effective masses mnc along /1 0 0S in LaRu4 P12 Experiment
90kOe
1/H
Branch
F ð107 OeÞ
mnc =m0
F ð107 OeÞ
mnc =m0
a
5.8
2.9
5.5
1.8
ln{A[1-exp(-2λm*CT/H)]/ T} (arb. units)
120kOe
α
mC* = 2.93 ± 0.01m0
LaRu4P12 α = 5.8 x 107 Oe H || <100>
0.4
0
2
4
6
8
10
12
dHvA Frequency (107 Oe) Fig. 1. (a) The typical dHvA oscillations and (b) its fast Fourier transformation (FFT) spectrum in LaRu4 P12 :
Calculation
0.5
0.6
0.7
0.8
0.9
1.0
1.1
T (K) Fig. 2. The semi-logarithmic plot of the reduced dHvA amplitude A vs. temperature for a-branch in LaRu4 P12 : l in the vertical-axis label is a constant l ¼ 2p2 ckB =e_: The mnc was estimated at around 110 kOe:
70
S.R. Saha et al. / Physica B 328 (2003) 68–70
However, in order to detect those Fermi surfaces measurements should be extended to temperatures lower than 0:4 K:
Acknowledgements One of the authors (S.R. Saha) acknowledges the support of a fellowship from Japan Society for the Promotion of Science. This work has also been partly supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Science, Sports, and Technology of Japan.
References [1] C. Sekine, et al., Phys. Rev. Lett. 79 (1997) 3218; C. Sekine, et al., Physica B 281& 282 (2000) 303; C. Sekine, et al., Physica B 281& 282 (2000) 300. [2] H. Sato, et al., Phys. Rev. B 62 (2000) 15125; Y. Aoki, et al., Phys. Rev. B 65 (2002) 064446. [3] H. Sugawara, et al., J. Phys. Soc. Japan 69 (2000) 2938; H. Sugawara, et al., Phys. Rev. B 66 (2002) 134411. [4] I. Shirotani, et al., Phys. Rev. B 56 (1997) 7866. [5] C.H. Lee, et al., Phys. Rev. B 60 (1999) 13253; C.H. Lee, et al., J. Phys.: Condens. Matter 13 (2001) L45–48. [6] H. Harima, et al., Prog. Theor. Phys. Suppl. 138 (2000) 117; H. Harima, et al., Physica B 312–313 (2002) 843. [7] M.S. Torikachvili, et al., Phys. Rev. B 36 (1987) 8660. [8] S.R. Saha, et al. (in preparation).