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Transport properties of Yb0.8Y0.2InCu4 under high pressure
ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 272–276 (2004) 56–57
Transport properties of Yb0:8 Y0:2InCu4 under high pressure A. Mitsudaa,*, T. Ikenoa, Y. Nakanumaa, T. Kuwaia, Y. Isikawaa, W. Zhangb, K. Yoshimurab a
b
Department of Physics, Toyama University, 3190 Gofuku, Toyama 930-8555, Japan Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
Abstract We report electrical resistivity of Yb0:8 Y0:2 InCu4 as a function of temperature down to 0:1 K and pressure up to 2:1 GPa: As the valence transition temperature approaches zero temperature with applying pressure, an inflection point associated with weak ferromagnetic ordering is observed. The Curie temperature is insensitive to pressure up to 2:1 GPa: On the other hand, we observe no evidence of superconducting behavior for the present sample. r 2003 Elsevier B.V. All rights reserved. PACS: 64.70.Kb; 71.27.+a; 75.20.Hr Keywords: Valence transition; Yb compound; Pressure and substitution effect; Electrical resistivity; Weak ferromagnetism
YbInCu4 ; which crystallizes in the cubic AuBe5 -type structure, undergoes a first-order isostructural valence transition at Tv ¼ 42 K [1,2]. Above Tv ; the sample exhibits Curie–Weiss susceptibility with an effective moment near the Yb3þ ion. At T ¼ Tv ; the magnetic susceptibility drops drastically and is transformed into almost temperature-independent Pauli-paramagnetic behavior corresponding to Yb2:9þ : Substitution of Y for Yb lowers the Tv with retaining properties of the transition [3,4]. Applying pressure also lowers the Tv [5]. Recently, we investigated magnetization of Yb0:8 Y0:2 InCu4 ðTv ¼ 17 KÞ under high pressures up to 1:2 GPa at low temperatures down to 0:6 K: With applying pressure, the Tv approaches zero and almost simultaneously weak ferromagnetic behavior appears [6]. This ferromagnetism, which is characterized at 1:2 GPa by low Curie temperature ðTCurie Þ of 1:7 K and very small spontaneous magnetization of 0:05 mB =Yb; certainly gives us important information for better understanding of the mechanism of the valence transition. In the present study, we investigated electrical resistivity r at higher
*Corresponding author. Tel.: +81-76-445-6584; fax: +8176-445-6549. E-mail address: [email protected] (A. Mitsuda).
pressures up to 2:1 GPa and at lower temperatures down to 0:1 K: A single crystalline sample of Yb0:8 Y0:2 InCu4 was grown from an In–Cu flux as reported previously [2,4]. Here, we used the sample undergoing the valence transition at Tv ¼ 22 K under ambient pressure. The r was measured by a conventional DC four-probe method on the temperature decreasing. The hydrostatic pressure up to 2:1 GPa was generated in a piston cylinder-type pressure cell made of Cu–Be alloy filled with Daphne oil 7373 as pressure-transmitting medium. The sample inside the pressure cell was cooled by being attached on a 3 He–4 He dilution refrigerator. Fig. 1 shows normalized r as a function of temperature for various pressures. For Pp0:4 GPa; a sharp drop associated with the valence transition is clearly observed in the rðTÞ curves. For P ¼ 0:8 GPa; the drop becomes smaller and less sharp than that for Pp0:4 GPa: The Tv ; which is determined from the onset of the drop, is lowered linearly with increasing pressure. On the other hand, for PX1:2 GPa; the valence transition disappears. Instead, as shown in the inset of Fig. 1, an inflection point is observed at T B1:9 K; which is close to the TCurie of 1:7 K; estimated from the magnetization measurement [6]. The T is insensitive to pressure, which is similar to
0304-8853/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.1154
ARTICLE IN PRESS A. Mitsuda et al. / Journal of Magnetism and Magnetic Materials 272–276 (2004) 56–57
25
1.2
Yb0.8Y0.2InCu4
Yb0.8Y0.2InCu4 1
57
(GPa) 2.1
20 0.95
1.6
Tv 15
ρ/ρ40K
1.2
(GPa) 2.1
0.90
0.6
T (K)
0.8
0.8 0.85
0.4
1.2 GPa (0 T)
5
1.2 GPa (0.05 T)
0.2 0.80
0 (GPa) 0
10
T*
1.6
0.4
0
10
0
1
2
3
4
0 20
30
40
TCurie
50
T (K)
1
1.5 P (GPa)
2
2.5
Fig. 2. T–P phase diagram in Yb0:8 Y0:2 InCu4 :
Fig. 1. Temperature dependence of electrical resistivity r normalized by r at 40 K: The inset shows the data in the temperature range of 0–4 K:
the nature of the TCurie [6]. These features suggest that the inflection point corresponds to the weak ferromagnetic ordering. The present rðTÞ data indicate that the weak ferromagnetism is retained at high pressures up to 2:1 GPa: Recently, Hedo et al. [7] and Mito et al. [8] have independently reported the electrical resistivity of YbInCu4 at high pressures and at low temperatures. Hedo et al., observed a filamentary superconductivity, whereas Mito et al. did not observe any sign of superconducting transition. In this respect, our results agree with those of Mito et al. As shown in the inset of Fig. 1, the curve at P ¼ 1:2 GPa in a field of 0:05 T is almost the same as that in a zero field, although Hedo et al. reported that a small drop in resistivity at around 1:2 K vanishes in the identical field. Except for the superconducting behavior, our results are qualitatively similar to both groups’ ones. Mito et al. has reported a peak in dr=dT curves and ferromagnetic behavior of AC susceptibility in YbInCu4 under high pressure. Qualitative agreement between theirs and our results
0.5
suggests that YbInCu4 exhibits similar weak ferromagnetism to the case for Yb0:8 Y0:2 InCu4 : In conclusion, the T–P phase diagram is shown in Fig. 2. The Tv decreases linearly at a rate of dTv =dP ¼ 15:3 K=GPa and vanishes above 1:2 GPa; where the pressure-independent TCurie is observed up to 2:1 GPa: The phase diagram is qualitatively similar to our previous result [6]. Finally, we observe no evidence of superconductivity.
References [1] [2] [3] [4] [5] [6] [7] [8]
I. Felner, I. Nowik, Phys. Rev. B 33 (1986) 617. J.L. Sarrao, et al., Phys. Rev. B 54 (1996) 12207. H. Nakamura, M. Shiga, Physica B 206, 207 (1995) 364. W. Zhang, et al., Phys. Rev. B 66 (2002) 024112. I. Nowik, et al., Phys. Rev. B 37 (1988) 5633. A. Mitsuda, et al., Phys. Rev. Lett. 88 (2002) 137204. M. Hedo, et al., Acta Phys. Pol. B 34 (2003) 1193. T. Mito, et al., Phys. Rev. B 67 (2003) 224409.
Journal of Magnetism and Magnetic Materials 272–276 (2004) 56–57
Transport properties of Yb0:8 Y0:2InCu4 under high pressure A. Mitsudaa,*, T. Ikenoa, Y. Nakanumaa, T. Kuwaia, Y. Isikawaa, W. Zhangb, K. Yoshimurab a
b
Department of Physics, Toyama University, 3190 Gofuku, Toyama 930-8555, Japan Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
Abstract We report electrical resistivity of Yb0:8 Y0:2 InCu4 as a function of temperature down to 0:1 K and pressure up to 2:1 GPa: As the valence transition temperature approaches zero temperature with applying pressure, an inflection point associated with weak ferromagnetic ordering is observed. The Curie temperature is insensitive to pressure up to 2:1 GPa: On the other hand, we observe no evidence of superconducting behavior for the present sample. r 2003 Elsevier B.V. All rights reserved. PACS: 64.70.Kb; 71.27.+a; 75.20.Hr Keywords: Valence transition; Yb compound; Pressure and substitution effect; Electrical resistivity; Weak ferromagnetism
YbInCu4 ; which crystallizes in the cubic AuBe5 -type structure, undergoes a first-order isostructural valence transition at Tv ¼ 42 K [1,2]. Above Tv ; the sample exhibits Curie–Weiss susceptibility with an effective moment near the Yb3þ ion. At T ¼ Tv ; the magnetic susceptibility drops drastically and is transformed into almost temperature-independent Pauli-paramagnetic behavior corresponding to Yb2:9þ : Substitution of Y for Yb lowers the Tv with retaining properties of the transition [3,4]. Applying pressure also lowers the Tv [5]. Recently, we investigated magnetization of Yb0:8 Y0:2 InCu4 ðTv ¼ 17 KÞ under high pressures up to 1:2 GPa at low temperatures down to 0:6 K: With applying pressure, the Tv approaches zero and almost simultaneously weak ferromagnetic behavior appears [6]. This ferromagnetism, which is characterized at 1:2 GPa by low Curie temperature ðTCurie Þ of 1:7 K and very small spontaneous magnetization of 0:05 mB =Yb; certainly gives us important information for better understanding of the mechanism of the valence transition. In the present study, we investigated electrical resistivity r at higher
*Corresponding author. Tel.: +81-76-445-6584; fax: +8176-445-6549. E-mail address: [email protected] (A. Mitsuda).
pressures up to 2:1 GPa and at lower temperatures down to 0:1 K: A single crystalline sample of Yb0:8 Y0:2 InCu4 was grown from an In–Cu flux as reported previously [2,4]. Here, we used the sample undergoing the valence transition at Tv ¼ 22 K under ambient pressure. The r was measured by a conventional DC four-probe method on the temperature decreasing. The hydrostatic pressure up to 2:1 GPa was generated in a piston cylinder-type pressure cell made of Cu–Be alloy filled with Daphne oil 7373 as pressure-transmitting medium. The sample inside the pressure cell was cooled by being attached on a 3 He–4 He dilution refrigerator. Fig. 1 shows normalized r as a function of temperature for various pressures. For Pp0:4 GPa; a sharp drop associated with the valence transition is clearly observed in the rðTÞ curves. For P ¼ 0:8 GPa; the drop becomes smaller and less sharp than that for Pp0:4 GPa: The Tv ; which is determined from the onset of the drop, is lowered linearly with increasing pressure. On the other hand, for PX1:2 GPa; the valence transition disappears. Instead, as shown in the inset of Fig. 1, an inflection point is observed at T B1:9 K; which is close to the TCurie of 1:7 K; estimated from the magnetization measurement [6]. The T is insensitive to pressure, which is similar to
0304-8853/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.1154
ARTICLE IN PRESS A. Mitsuda et al. / Journal of Magnetism and Magnetic Materials 272–276 (2004) 56–57
25
1.2
Yb0.8Y0.2InCu4
Yb0.8Y0.2InCu4 1
57
(GPa) 2.1
20 0.95
1.6
Tv 15
ρ/ρ40K
1.2
(GPa) 2.1
0.90
0.6
T (K)
0.8
0.8 0.85
0.4
1.2 GPa (0 T)
5
1.2 GPa (0.05 T)
0.2 0.80
0 (GPa) 0
10
T*
1.6
0.4
0
10
0
1
2
3
4
0 20
30
40
TCurie
50
T (K)
1
1.5 P (GPa)
2
2.5
Fig. 2. T–P phase diagram in Yb0:8 Y0:2 InCu4 :
Fig. 1. Temperature dependence of electrical resistivity r normalized by r at 40 K: The inset shows the data in the temperature range of 0–4 K:
the nature of the TCurie [6]. These features suggest that the inflection point corresponds to the weak ferromagnetic ordering. The present rðTÞ data indicate that the weak ferromagnetism is retained at high pressures up to 2:1 GPa: Recently, Hedo et al. [7] and Mito et al. [8] have independently reported the electrical resistivity of YbInCu4 at high pressures and at low temperatures. Hedo et al., observed a filamentary superconductivity, whereas Mito et al. did not observe any sign of superconducting transition. In this respect, our results agree with those of Mito et al. As shown in the inset of Fig. 1, the curve at P ¼ 1:2 GPa in a field of 0:05 T is almost the same as that in a zero field, although Hedo et al. reported that a small drop in resistivity at around 1:2 K vanishes in the identical field. Except for the superconducting behavior, our results are qualitatively similar to both groups’ ones. Mito et al. has reported a peak in dr=dT curves and ferromagnetic behavior of AC susceptibility in YbInCu4 under high pressure. Qualitative agreement between theirs and our results
0.5
suggests that YbInCu4 exhibits similar weak ferromagnetism to the case for Yb0:8 Y0:2 InCu4 : In conclusion, the T–P phase diagram is shown in Fig. 2. The Tv decreases linearly at a rate of dTv =dP ¼ 15:3 K=GPa and vanishes above 1:2 GPa; where the pressure-independent TCurie is observed up to 2:1 GPa: The phase diagram is qualitatively similar to our previous result [6]. Finally, we observe no evidence of superconductivity.
References [1] [2] [3] [4] [5] [6] [7] [8]
I. Felner, I. Nowik, Phys. Rev. B 33 (1986) 617. J.L. Sarrao, et al., Phys. Rev. B 54 (1996) 12207. H. Nakamura, M. Shiga, Physica B 206, 207 (1995) 364. W. Zhang, et al., Phys. Rev. B 66 (2002) 024112. I. Nowik, et al., Phys. Rev. B 37 (1988) 5633. A. Mitsuda, et al., Phys. Rev. Lett. 88 (2002) 137204. M. Hedo, et al., Acta Phys. Pol. B 34 (2003) 1193. T. Mito, et al., Phys. Rev. B 67 (2003) 224409.