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Pressure effect on PuMGa5 systems (M=Co , Rh, Ir)
ARTICLE IN PRESS
Physica B 359–361 (2005) 1093–1095 www.elsevier.com/locate/physb
Pressure effect on PuMGa5 systems (M ¼ Co; Rh, Ir) Jean-Christophe Griveau, Pascal Boulet, Eric Colineau, Franck Wastin, Jean Rebizant European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe, Germany
Abstract We report high-pressure resistivity of PuMGa5 (M ¼ Co; Rh, Ir) up to 20 GPa from 300 down to 1.4 K. For PuCoGa5 and PuRhGa5 ; superconductivity takes place over the whole pressure domain investigated and a non-Fermi liquid behaviour (rðTÞ T 1:3 ) in the normal state is observed. A strong correlation between the temperature–pressure diagrams of PuðCo; RhÞGa5 and CeðCo; IrÞIn5 is inferred. Interestingly, PuIrGa5 does not show superconductivity up to 10 GPa and down to 1.4 K but rather develops a Fermi liquid regime. r 2005 Elsevier B.V. All rights reserved. PACS: 74.25.Dw; 74.62.Fj; 74.25.Fy Keywords: Superconductivity; Actinides; Pressure
PuCoGa5 [1] and PuRhGa5 [2] are the first plutonium-based superconductors discovered. They display noticeable differences compared to 4f or 5f heavy Fermion superconductors (HFS). Their transition temperature (T c 18:5 K and 9 K; respectively) are ten times higher than the HFS (T c 1 K) or their cerium isostructural counterparts [3]. Evolution of T c and rðTÞ with pressure may yield information about the mechanism at the origin of the pairing effect and provide information about possible unconventional superCorresponding author. Tel.: +49 7247 951 428;
fax: +49 7247 951 99 428. E-mail address: [email protected] (J.-C. Griveau).
conductivity. For this purpose, electrical resistivity measurements under pressure have been carried out on PuMGa5 systems (M ¼ Co; Rh, Ir). The measurements were performed on samples with typical size close to 500 100 50 mm3 : The pressure devices, the loading protocol and resistivity measurements techniques have been previously described [4]. High-pressure measurements on PuCoGa5 have been obtained up to 16.5 GPa [4]. With increasing pressure, the metallic character of the electrical resistance is reinforced. T c increases from 19 to 23 K but the superconducting transition width is extended with pressure. Low-temperature resistivity in the normal state above T c exhibits a NFL
0921-4526/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2005.01.296
ARTICLE IN PRESS J.-C. Griveau et al. / Physica B 359– 361 (2005) 1093–1095
1094
behaviour with a T 1:34 law from T c to 50 K (possible 2D ferromagnetic fluctuations). The resistance behaviour of PuRhGa5 is close to that of PuCoGa5 : It displays a metallic shape (Fig. 1) in the normal state. Here too, a NFL behaviour develops up to 50–60 K. With increasing pressure, T c drastically increases and reaches values close to that of PuCoGa5 at ambient pressure. From about 16 K at 10 GPa, it then decreases with pressure, the material remaining superconducting up to 20 GPa. However, a large broadening of the superconducting transition width is observed ( 6 K at 18.7 GPa). Above T c ; we observe initially a general decrease of resistance with pressure for both compounds, that may be associated with variation of the form factor. However, around 10 GPa, there is an upturn, the resistance increases and the T c of the two compounds evolves differently with pressure. This may indicate that pairing mechanism is differently affected by pressure. The NFL character of the electrical resistivity as well as the superconducting state are still present in both materials up to 20 GPa (insert Fig. 1). Recent electronic structure calculations [5] suggest that the pairing of plutonium 5f electrons may be responsible for the superconductivity in
125
20
24
PuCoGa5
16
PuRhGa5 0
50
5
10
15
12
15
R (mΩ)
75
Tc(K)
100
1.7 GPa 6.2 GPa 9.5 GPa 2 R0(P) + a(P) T
PuIrGa5
PuRhGa5
20
R (mΩ)
PuCoGa5 : For PuRhGa5 ; experimental results at 10 GPa indicate a reduction of pairing mechanism (structural or magnetic transition?). Compressibility measurements are required on both materials. The layered crystal structure associated with the quasi-2D Fermi surface calculated for these materials [6] suggests possible anisotropic properties. The strong influence of the pressure on the transition width which may be due to experimental pressure conditions can also be indicative of intrinsic anisotropy, as recently observed in NpCoGa5 [7]. The case of PuIrGa5 is clearly different (Fig. 2). Resistivity measurements on bulk samples do not show any hint of superconductivity down to 2 K. Pressure measurements on a sample isolated from the bulk material confirm these results with a clear Fermi liquid regime developing up to 50 K. With pressure, the residual resistivity strongly decreases, but up to 9.5 GPa no superconducting transition is induced in this material down to 1.4 K. The temperature–pressure (T–P) phase diagram obtained for PuMGa5 (M ¼ Co; Rh) can be compared to that of CeCoIn5 [8]. In all three isostructural compounds, the superconducting transition temperature increases with increasing pressure and goes through a maximum before
8 20
10
P (GPa) 5
1.6 GPa 2.8 GPa 9.4 GPa 18.7 GPa
25
0
0 0
100
200
300
T (K) Fig. 1. Evolution of the electrical resistance of PuRhGa5 crystal up to 18.7 GPa. The insert shows T c behaviour of PuCoGa5 and PuRhGa5 as a function of the applied pressure.
0
20
40
60
80
T (K) Fig. 2. Evolution of the electrical resistance of PuIrGa5 crystal up to 9.5 GPa. The R0 ðPÞ þ aðPÞT 2 lines represent the Fermi liquid fits.
ARTICLE IN PRESS J.-C. Griveau et al. / Physica B 359– 361 (2005) 1093–1095
decreasing at higher pressure. The pressure domains in which this behaviour takes place is drastically extended in the case of Pu-compounds (15–20 GPa) compared to the Ce-compounds (3–4 GPa). Similarly, the NFL behaviour is maintained over a large pressure range. Interestingly, PuIrGa5 does not present any hint of superconductivity down to 1.4 K and up to 9.5 GPa but rather displays a low-temperature FL regime. The presented results and recent proposed analysis [9] suggest strong correlation between the isostructural Pu and Ce 1:1:5 compounds. The high-purity Pu metals required for the fabrication of the compound were made available through a loan agreement between Lawrence Livermore National Laboratory and ITU, in the frame of a collaboration involving LLNL, Los Alamos National Laboratory and the US Department of Energy.
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References [1] J.L. Sarrao, L.A. Morales, J.D. Thompson, B.L. Scott, G.R. Stewart, F. Wastin, J. Rebizant, P. Boulet, E. Colineau, G.H. Lander, Nature 420 (2002) 297. [2] F. Wastin, P. Boulet, J. Rebizant, E. Colineau, G.H. Lander, J. Phys.: Condens. Matter 15 (2003) 2279. [3] C. Petrovic, R. Movshovich, M. Jaime, P.G. Pagliuso, M.F. Hundley, J.L. Sarrao, Z. Fisk, J.D. Thompson, J. Phys.: Condens. Matter 13 (2001) L337. [4] J.-C. Griveau, C. Pfleiderer, P. Boulet, J. Rebizant, F. Wastin, J. Magn. Magn. Mater. 272–276 (2004) 154. [5] I. Opahle, P.M. Oppeneer, Phys. Rev. Lett. 90 (2004) 157001. [6] T. Hotta, K. Ueda, Phys. Rev. B 67 (2003) 104518. [7] E. Colineau, P. Javorsky, P. Boulet, F. Wastin, J.-C. Griveau, J. Rebizant, J.P. Sanchez, G.R. Stewart, Phys. Rev. B 69 (2004) 184411. [8] V.A. Sidorov, M. Nicklas, P.G. Pagliuso, J.L. Sarrao, Y. Bang, A.V. Balatsky, J.D. Thompson, Phys. Rev. Lett. 89 (2002) 157004. [9] E.D. Bauer, J.D. Thompson, J.L. Sarrao, L.A. Morales, F. Wastin, J. Rebizant, et al., Phys. Rev. Lett. 93 (2004) 147005.
Physica B 359–361 (2005) 1093–1095 www.elsevier.com/locate/physb
Pressure effect on PuMGa5 systems (M ¼ Co; Rh, Ir) Jean-Christophe Griveau, Pascal Boulet, Eric Colineau, Franck Wastin, Jean Rebizant European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe, Germany
Abstract We report high-pressure resistivity of PuMGa5 (M ¼ Co; Rh, Ir) up to 20 GPa from 300 down to 1.4 K. For PuCoGa5 and PuRhGa5 ; superconductivity takes place over the whole pressure domain investigated and a non-Fermi liquid behaviour (rðTÞ T 1:3 ) in the normal state is observed. A strong correlation between the temperature–pressure diagrams of PuðCo; RhÞGa5 and CeðCo; IrÞIn5 is inferred. Interestingly, PuIrGa5 does not show superconductivity up to 10 GPa and down to 1.4 K but rather develops a Fermi liquid regime. r 2005 Elsevier B.V. All rights reserved. PACS: 74.25.Dw; 74.62.Fj; 74.25.Fy Keywords: Superconductivity; Actinides; Pressure
PuCoGa5 [1] and PuRhGa5 [2] are the first plutonium-based superconductors discovered. They display noticeable differences compared to 4f or 5f heavy Fermion superconductors (HFS). Their transition temperature (T c 18:5 K and 9 K; respectively) are ten times higher than the HFS (T c 1 K) or their cerium isostructural counterparts [3]. Evolution of T c and rðTÞ with pressure may yield information about the mechanism at the origin of the pairing effect and provide information about possible unconventional superCorresponding author. Tel.: +49 7247 951 428;
fax: +49 7247 951 99 428. E-mail address: [email protected] (J.-C. Griveau).
conductivity. For this purpose, electrical resistivity measurements under pressure have been carried out on PuMGa5 systems (M ¼ Co; Rh, Ir). The measurements were performed on samples with typical size close to 500 100 50 mm3 : The pressure devices, the loading protocol and resistivity measurements techniques have been previously described [4]. High-pressure measurements on PuCoGa5 have been obtained up to 16.5 GPa [4]. With increasing pressure, the metallic character of the electrical resistance is reinforced. T c increases from 19 to 23 K but the superconducting transition width is extended with pressure. Low-temperature resistivity in the normal state above T c exhibits a NFL
0921-4526/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2005.01.296
ARTICLE IN PRESS J.-C. Griveau et al. / Physica B 359– 361 (2005) 1093–1095
1094
behaviour with a T 1:34 law from T c to 50 K (possible 2D ferromagnetic fluctuations). The resistance behaviour of PuRhGa5 is close to that of PuCoGa5 : It displays a metallic shape (Fig. 1) in the normal state. Here too, a NFL behaviour develops up to 50–60 K. With increasing pressure, T c drastically increases and reaches values close to that of PuCoGa5 at ambient pressure. From about 16 K at 10 GPa, it then decreases with pressure, the material remaining superconducting up to 20 GPa. However, a large broadening of the superconducting transition width is observed ( 6 K at 18.7 GPa). Above T c ; we observe initially a general decrease of resistance with pressure for both compounds, that may be associated with variation of the form factor. However, around 10 GPa, there is an upturn, the resistance increases and the T c of the two compounds evolves differently with pressure. This may indicate that pairing mechanism is differently affected by pressure. The NFL character of the electrical resistivity as well as the superconducting state are still present in both materials up to 20 GPa (insert Fig. 1). Recent electronic structure calculations [5] suggest that the pairing of plutonium 5f electrons may be responsible for the superconductivity in
125
20
24
PuCoGa5
16
PuRhGa5 0
50
5
10
15
12
15
R (mΩ)
75
Tc(K)
100
1.7 GPa 6.2 GPa 9.5 GPa 2 R0(P) + a(P) T
PuIrGa5
PuRhGa5
20
R (mΩ)
PuCoGa5 : For PuRhGa5 ; experimental results at 10 GPa indicate a reduction of pairing mechanism (structural or magnetic transition?). Compressibility measurements are required on both materials. The layered crystal structure associated with the quasi-2D Fermi surface calculated for these materials [6] suggests possible anisotropic properties. The strong influence of the pressure on the transition width which may be due to experimental pressure conditions can also be indicative of intrinsic anisotropy, as recently observed in NpCoGa5 [7]. The case of PuIrGa5 is clearly different (Fig. 2). Resistivity measurements on bulk samples do not show any hint of superconductivity down to 2 K. Pressure measurements on a sample isolated from the bulk material confirm these results with a clear Fermi liquid regime developing up to 50 K. With pressure, the residual resistivity strongly decreases, but up to 9.5 GPa no superconducting transition is induced in this material down to 1.4 K. The temperature–pressure (T–P) phase diagram obtained for PuMGa5 (M ¼ Co; Rh) can be compared to that of CeCoIn5 [8]. In all three isostructural compounds, the superconducting transition temperature increases with increasing pressure and goes through a maximum before
8 20
10
P (GPa) 5
1.6 GPa 2.8 GPa 9.4 GPa 18.7 GPa
25
0
0 0
100
200
300
T (K) Fig. 1. Evolution of the electrical resistance of PuRhGa5 crystal up to 18.7 GPa. The insert shows T c behaviour of PuCoGa5 and PuRhGa5 as a function of the applied pressure.
0
20
40
60
80
T (K) Fig. 2. Evolution of the electrical resistance of PuIrGa5 crystal up to 9.5 GPa. The R0 ðPÞ þ aðPÞT 2 lines represent the Fermi liquid fits.
ARTICLE IN PRESS J.-C. Griveau et al. / Physica B 359– 361 (2005) 1093–1095
decreasing at higher pressure. The pressure domains in which this behaviour takes place is drastically extended in the case of Pu-compounds (15–20 GPa) compared to the Ce-compounds (3–4 GPa). Similarly, the NFL behaviour is maintained over a large pressure range. Interestingly, PuIrGa5 does not present any hint of superconductivity down to 1.4 K and up to 9.5 GPa but rather displays a low-temperature FL regime. The presented results and recent proposed analysis [9] suggest strong correlation between the isostructural Pu and Ce 1:1:5 compounds. The high-purity Pu metals required for the fabrication of the compound were made available through a loan agreement between Lawrence Livermore National Laboratory and ITU, in the frame of a collaboration involving LLNL, Los Alamos National Laboratory and the US Department of Energy.
1095
References [1] J.L. Sarrao, L.A. Morales, J.D. Thompson, B.L. Scott, G.R. Stewart, F. Wastin, J. Rebizant, P. Boulet, E. Colineau, G.H. Lander, Nature 420 (2002) 297. [2] F. Wastin, P. Boulet, J. Rebizant, E. Colineau, G.H. Lander, J. Phys.: Condens. Matter 15 (2003) 2279. [3] C. Petrovic, R. Movshovich, M. Jaime, P.G. Pagliuso, M.F. Hundley, J.L. Sarrao, Z. Fisk, J.D. Thompson, J. Phys.: Condens. Matter 13 (2001) L337. [4] J.-C. Griveau, C. Pfleiderer, P. Boulet, J. Rebizant, F. Wastin, J. Magn. Magn. Mater. 272–276 (2004) 154. [5] I. Opahle, P.M. Oppeneer, Phys. Rev. Lett. 90 (2004) 157001. [6] T. Hotta, K. Ueda, Phys. Rev. B 67 (2003) 104518. [7] E. Colineau, P. Javorsky, P. Boulet, F. Wastin, J.-C. Griveau, J. Rebizant, J.P. Sanchez, G.R. Stewart, Phys. Rev. B 69 (2004) 184411. [8] V.A. Sidorov, M. Nicklas, P.G. Pagliuso, J.L. Sarrao, Y. Bang, A.V. Balatsky, J.D. Thompson, Phys. Rev. Lett. 89 (2002) 157004. [9] E.D. Bauer, J.D. Thompson, J.L. Sarrao, L.A. Morales, F. Wastin, J. Rebizant, et al., Phys. Rev. Lett. 93 (2004) 147005.