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Resistivity and superconductivity of uranium based metallic glasses
Physica B 165&166 (1990) 1519-1520 North-Holland
Resistivity and Superconductivity of Uranium Based Metallic Glasses E.-W. Scheidt, H. Riesemeier, K. Liiders Freie Universitiit Berlin, Fachbereich Physik, Arnimallee 14, D-I000 Berlin 33, FRG M. Robrecht, J. Hasse Universitiit Karlsruhe, Physikalisches Institut, Engesserstr. 7, D-7500 Karlsruhe 1, FRG Amorphous U-Fe, U-Co and U-Ni alloys were prepared by splat quenching over the uranium concentration range of 50 - 83 at%. The temperature dependence of the electrical resistivity, peT), was investigated in the range of 4.2 - 300 K. The results below the Debye temperature (8 ~ 165 K) may be explained within the frame of the extended Ziman theory and the paramagnon model. The concentration dependence of p and of the superconducting transition temperature T e might be explained by the variation of the d-electron contribution.
1. INTRODUCTION The amorphous U-X alloys (X = Fe, Co, Ni) are superconducting in a wide concentration range on the uranium rich side [1-3]. The highest Te-values are obtained for the 3d-component (Fe) with the lowest number of d-electron whereas the lowest Te-values are obtained for those with the highest number of d-electrons (Ni). This is just opposite to the behaviour of the corresponding zirconium based metallic glasses [4]. Therefore, the influence of the 5f-electrons of U on the electronic transport properties is of particular interest. Further interest results from the fact that the crystalline compounds U6 Fe and U6 Co belong to the moderately heavy fermion systems. In this contribution the concentration dependence of the resistivity p and the superconducting transition temperature T e are investigated in a wide concentration range and discussed in connection with the variation of the d-electrons per atom. With the measured temperature dependence of p and the extended Ziman theory values of the Fermi wave numbers, k F , and of the mean free paths of the conduction electrons, £0, are estimated. 2. EXPERIMENTAL The samples were prepared by the splat-quench technique. The amorphous state was checked by X-ray diffraction. The resistivity measurements were carried out with the usual dc-four-probe technique. In each case the oxid surface layer was removed by means of mechanical grindin§. T e was determined via resistivity measurements in a Hej4He dilution refrigerator (basis temperature: 13 mK). 3. RESULTS AND DISCUSSION The temperature dependence of the resistivity was measured for all samples listed in Table 1. The p(T)curves shown in Fig. 1 for two selected samples exhibit a characteristic behaviour which was observed for all samples with negative temperature coefficient a. The solid lines in Fig. 1 are fits to the experimental data. 0921-4526/90/$03.50
© 1990 -
Table 1 Superconducting transition temperature T e, resistivity p (4.2 K), temperature coefficient a, Fermi wave number kF , and mean free path £0 of the conduction electrons.
Us1 Fe19 U66 Fe34 Uso Fe40 U50 F e50 U75 C0 25 U66 C034 USO Co40 U54 C04S Us3 Ni 17 U75 Ni 25 Uss Ni 34 Uso Ni 40
Te (mK) ±0.5% 952 872 835 789 577 437 277 163 500 268 114 <13
p(4.2K) (Il ncm ) ±7% 91 96 144 111 113 118 136 139 50 92 125 138
a
(7)
±10% -99 -120 -178 +150 -90 -160 -140 -230 +1570 +162 -94 -60
kF
£0
(A -1)
(A)
±8% 1.37 1.34 1.33 1.32 1.35 1.31 1.29 1.26 1.37 1.35 1.32 1.3
±10% 7.1 7.0 4.7 6.2 6 6 5.4 5.5 13 7.2 5.5 5.2
In the low temperature region peT) follows a parabolic dependence: peT) ex 1 - AT2. At higher temperatures p is linear in T up to a certain temperature which corresponds approximately to the Debye temperature obtained in specific heat measurements (8 = 155 K - 175 K [5]). The a-values of the linear parts and the p-values for T = 4.2 K are summarized in Table 1. The peT) results may be described within the frame of an extended Ziman theory as discussed for Zr based metallic glasses [6]. Especially the (1 - AT2) behaviour at low temperatures may be explained by the strong scattering model (p > 100jlncm) of Cote and Meisel [7]. On the other hand a satisfactory description of the p(T)-behaviour may also be obtained in terms of the paramagnon model [1,2].
Elsevier Science Publishers B.V. (North-Holland)
1520
E.- W. Scheidt, H. Riesemeier, K. Lfiders, M. Robrecht, J. Hasse
:::.c::
...... u I-
1.0 r--~---r-.,--,------r-'-~----"T=--'-----'
~ UFe
0.5
UCo
UNi
o. 0 '-------'------'----"---'---"'--'----'---'-----'-~----' E 160 r--~___,__----,--,----,---,-----,--,----,------, U
c::L O.950k-~~~----'-1*OO----~~~--;2dO"'O'---"--~~='300
Kt~_Ni
'U~
...... 120
~
OJ
temperature / K
Fig. 1. Temperature dependence of the normalized resistivity for two selected samples. The lines are parabolic and linear fits.
80 '-:-~___;=,::O_~~~-~~;:----'-\ --;;;:':;<--'-----,;:' 40 50 60 70 80 90 uranium concentration / at%
I
cc:{
...... 3.00
Fig. 3. V-concentration dependence of the superconducting transition temperature T e , and the resistivity pat 4.2 K.
.::.t.~
C\J L.
2.75
o
~O- 2.50
2.25 2.00 40
50
60
70
80
90
uranium concentration / at%
Fig. 2. V-concentration dependence of the scattering vector kp corresponding to the maximum of the main peak in the X-ray interference function. (0 V-Fe, 0 VCo, 0 V-Ni.) The average half width of these peaks is indicated. 2kF-values has been calculated for different electron numbers per V-atom, Zu. From the extended Ziman theory a negative temperature coefficient is expected for kp = 2kF (kp is the maximum of the main peak in the interference function as obtained from X-ray diffraction, k F is the Fermi wave number). Fig.. 2 shows the experimental kp-values in comparison with 2kp-values calculated in the free electron model with the weighted conduction electron number Z = xZu + (l-x)ZTM (x = Vconcentration, Zu and ZTM are the s-like electron numbers per atom for V and the transition metals (Fe, Co, Ni), respectively). With ZTM = 0.6 [6] agreement is obtained for Zu = 2. The resulting kF-values are listed in Table 1. Vsing the values of kF and p (4.2 K) the mean free paths f o of the conduction electrons are calculated in the free electron model (Table 1).
The concentration dependence of p is plotted in Fig. 3. In general, p increases when going from V-Fe to V-Co and V-Ni and with decreasing V-concentration. (The deviation of the samples Vs3 Ni 17 and V 60 F 40 may be due to crystalline inclusions and to mixtures of different concentrations, respectively.) This behaviour may be explained by an increase of the d-electron concentration due to the shift of the 3d-band to higher energies [8]. This leads to a larger influence of the felectrons at the Fermi surface. Therefore one would expect a reduction of the superconducting transition temperature which is in agreement with the experimental results (Fig. 3). REFERENCES (1) S.J. Poon, A.J. Drehman, K.M. Wong, A.W. Clegg, Phys. Rev. B31 (1985) 3100. (2) K.M. Wong, A.J. Drehman, S.J. Poon, Physica 135 B (1985) 299. (3) E.-W. Scheidt, H. Riesemeier, K. Liiders, G. Indlekofer, P. Oelhafen, H.-J. Giintherodt, M. Robrecht, Physica 148 B (1987) 58. (4) Z. Altounian, J. Strom-Olsen, Phys. Rev. B27 (1983) 4149. (5) M. Robrecht, J. Hasse, E.-W. Scheidt, K. Liiders, to be published. (6) K.H.J. Buschow, N.M. Beekmans, Phys. Rev. B19 (1979) 3843. (7) P.J. Cote, L.V. Meisel, Phys. Rev. Lett. 40 (1978) 1586. (8) P. Oelhafen, G. Indlekofer, J. Krieg, R. Lapka, V.M. Gubler, H.-J. Giintherodt, C.F. Hague, J. Mariot, Non-Cryst. Sol. 61/62 (1984) 1067.
Resistivity and Superconductivity of Uranium Based Metallic Glasses E.-W. Scheidt, H. Riesemeier, K. Liiders Freie Universitiit Berlin, Fachbereich Physik, Arnimallee 14, D-I000 Berlin 33, FRG M. Robrecht, J. Hasse Universitiit Karlsruhe, Physikalisches Institut, Engesserstr. 7, D-7500 Karlsruhe 1, FRG Amorphous U-Fe, U-Co and U-Ni alloys were prepared by splat quenching over the uranium concentration range of 50 - 83 at%. The temperature dependence of the electrical resistivity, peT), was investigated in the range of 4.2 - 300 K. The results below the Debye temperature (8 ~ 165 K) may be explained within the frame of the extended Ziman theory and the paramagnon model. The concentration dependence of p and of the superconducting transition temperature T e might be explained by the variation of the d-electron contribution.
1. INTRODUCTION The amorphous U-X alloys (X = Fe, Co, Ni) are superconducting in a wide concentration range on the uranium rich side [1-3]. The highest Te-values are obtained for the 3d-component (Fe) with the lowest number of d-electron whereas the lowest Te-values are obtained for those with the highest number of d-electrons (Ni). This is just opposite to the behaviour of the corresponding zirconium based metallic glasses [4]. Therefore, the influence of the 5f-electrons of U on the electronic transport properties is of particular interest. Further interest results from the fact that the crystalline compounds U6 Fe and U6 Co belong to the moderately heavy fermion systems. In this contribution the concentration dependence of the resistivity p and the superconducting transition temperature T e are investigated in a wide concentration range and discussed in connection with the variation of the d-electrons per atom. With the measured temperature dependence of p and the extended Ziman theory values of the Fermi wave numbers, k F , and of the mean free paths of the conduction electrons, £0, are estimated. 2. EXPERIMENTAL The samples were prepared by the splat-quench technique. The amorphous state was checked by X-ray diffraction. The resistivity measurements were carried out with the usual dc-four-probe technique. In each case the oxid surface layer was removed by means of mechanical grindin§. T e was determined via resistivity measurements in a Hej4He dilution refrigerator (basis temperature: 13 mK). 3. RESULTS AND DISCUSSION The temperature dependence of the resistivity was measured for all samples listed in Table 1. The p(T)curves shown in Fig. 1 for two selected samples exhibit a characteristic behaviour which was observed for all samples with negative temperature coefficient a. The solid lines in Fig. 1 are fits to the experimental data. 0921-4526/90/$03.50
© 1990 -
Table 1 Superconducting transition temperature T e, resistivity p (4.2 K), temperature coefficient a, Fermi wave number kF , and mean free path £0 of the conduction electrons.
Us1 Fe19 U66 Fe34 Uso Fe40 U50 F e50 U75 C0 25 U66 C034 USO Co40 U54 C04S Us3 Ni 17 U75 Ni 25 Uss Ni 34 Uso Ni 40
Te (mK) ±0.5% 952 872 835 789 577 437 277 163 500 268 114 <13
p(4.2K) (Il ncm ) ±7% 91 96 144 111 113 118 136 139 50 92 125 138
a
(7)
±10% -99 -120 -178 +150 -90 -160 -140 -230 +1570 +162 -94 -60
kF
£0
(A -1)
(A)
±8% 1.37 1.34 1.33 1.32 1.35 1.31 1.29 1.26 1.37 1.35 1.32 1.3
±10% 7.1 7.0 4.7 6.2 6 6 5.4 5.5 13 7.2 5.5 5.2
In the low temperature region peT) follows a parabolic dependence: peT) ex 1 - AT2. At higher temperatures p is linear in T up to a certain temperature which corresponds approximately to the Debye temperature obtained in specific heat measurements (8 = 155 K - 175 K [5]). The a-values of the linear parts and the p-values for T = 4.2 K are summarized in Table 1. The peT) results may be described within the frame of an extended Ziman theory as discussed for Zr based metallic glasses [6]. Especially the (1 - AT2) behaviour at low temperatures may be explained by the strong scattering model (p > 100jlncm) of Cote and Meisel [7]. On the other hand a satisfactory description of the p(T)-behaviour may also be obtained in terms of the paramagnon model [1,2].
Elsevier Science Publishers B.V. (North-Holland)
1520
E.- W. Scheidt, H. Riesemeier, K. Lfiders, M. Robrecht, J. Hasse
:::.c::
...... u I-
1.0 r--~---r-.,--,------r-'-~----"T=--'-----'
~ UFe
0.5
UCo
UNi
o. 0 '-------'------'----"---'---"'--'----'---'-----'-~----' E 160 r--~___,__----,--,----,---,-----,--,----,------, U
c::L O.950k-~~~----'-1*OO----~~~--;2dO"'O'---"--~~='300
Kt~_Ni
'U~
...... 120
~
OJ
temperature / K
Fig. 1. Temperature dependence of the normalized resistivity for two selected samples. The lines are parabolic and linear fits.
80 '-:-~___;=,::O_~~~-~~;:----'-\ --;;;:':;<--'-----,;:' 40 50 60 70 80 90 uranium concentration / at%
I
cc:{
...... 3.00
Fig. 3. V-concentration dependence of the superconducting transition temperature T e , and the resistivity pat 4.2 K.
.::.t.~
C\J L.
2.75
o
~O- 2.50
2.25 2.00 40
50
60
70
80
90
uranium concentration / at%
Fig. 2. V-concentration dependence of the scattering vector kp corresponding to the maximum of the main peak in the X-ray interference function. (0 V-Fe, 0 VCo, 0 V-Ni.) The average half width of these peaks is indicated. 2kF-values has been calculated for different electron numbers per V-atom, Zu. From the extended Ziman theory a negative temperature coefficient is expected for kp = 2kF (kp is the maximum of the main peak in the interference function as obtained from X-ray diffraction, k F is the Fermi wave number). Fig.. 2 shows the experimental kp-values in comparison with 2kp-values calculated in the free electron model with the weighted conduction electron number Z = xZu + (l-x)ZTM (x = Vconcentration, Zu and ZTM are the s-like electron numbers per atom for V and the transition metals (Fe, Co, Ni), respectively). With ZTM = 0.6 [6] agreement is obtained for Zu = 2. The resulting kF-values are listed in Table 1. Vsing the values of kF and p (4.2 K) the mean free paths f o of the conduction electrons are calculated in the free electron model (Table 1).
The concentration dependence of p is plotted in Fig. 3. In general, p increases when going from V-Fe to V-Co and V-Ni and with decreasing V-concentration. (The deviation of the samples Vs3 Ni 17 and V 60 F 40 may be due to crystalline inclusions and to mixtures of different concentrations, respectively.) This behaviour may be explained by an increase of the d-electron concentration due to the shift of the 3d-band to higher energies [8]. This leads to a larger influence of the felectrons at the Fermi surface. Therefore one would expect a reduction of the superconducting transition temperature which is in agreement with the experimental results (Fig. 3). REFERENCES (1) S.J. Poon, A.J. Drehman, K.M. Wong, A.W. Clegg, Phys. Rev. B31 (1985) 3100. (2) K.M. Wong, A.J. Drehman, S.J. Poon, Physica 135 B (1985) 299. (3) E.-W. Scheidt, H. Riesemeier, K. Liiders, G. Indlekofer, P. Oelhafen, H.-J. Giintherodt, M. Robrecht, Physica 148 B (1987) 58. (4) Z. Altounian, J. Strom-Olsen, Phys. Rev. B27 (1983) 4149. (5) M. Robrecht, J. Hasse, E.-W. Scheidt, K. Liiders, to be published. (6) K.H.J. Buschow, N.M. Beekmans, Phys. Rev. B19 (1979) 3843. (7) P.J. Cote, L.V. Meisel, Phys. Rev. Lett. 40 (1978) 1586. (8) P. Oelhafen, G. Indlekofer, J. Krieg, R. Lapka, V.M. Gubler, H.-J. Giintherodt, C.F. Hague, J. Mariot, Non-Cryst. Sol. 61/62 (1984) 1067.