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Electrical resistivity of uranium monosulphide
Journal
of the Less-Common
Metals,
90(1983)
L45-L48
L45
Letter Electrical resistivity of uranium monosulphide
R. TROC and L. KRAWCZYK Institute for Low Temperature and Structure Research, Polish Academy of Sciences, 50950 Wrodaw (Poland) (Received February 1,1983)
Introduction The electrical properties of uranium monosulphide (US) which is a ferromagnet at temperatures below about 180 K have been investigated by many workers. Most of these investigations were performed using sintered samples. The earliest measurements of the electrical resistivity of US were made below room temperature Cl-53 and at high temperatures up to 1500 “C [5,6]. Electrical resistivity data for US single crystals have recently been reported, but this information is only available in abstract form [7]. In this letter we report resistivity data for US single crystals measured as a function of temperature. The measurements were made in two directions ([loo] and [llO]) in order to detect any anisotropy in the resistivity behaviour. 1.
2. Experimental details The US was first prepared in powder form by direct reaction between the constituent elements as described in ref. 8. The polycrystalline US sample was heated in a closed tungsten crucible up to 2600 “C, i.e. about 150 “C above the melting point, and was then cooled to 2000 “C at a rate of 2 “C h- l. A fairly large single crystal was selected and several bar-shaped US samples were cut from it for the electrical measurements. An X-ray examination of the US single crystal using the Bond technique gave a value of 5.4847 fO.OOO1 A for the lattice constant. This value is close to that obtained by Kruger and Moser [9] and represents the lower limit of a wide range of lattice constants reported for US in the literature (see, for example, ref. 10). The quality of the single crystal obtained was rather high, as was shown by the fact that the X-ray linewidth was 10’. The electrical resistivity in the temperature range 4.2-300 K was measured by a standard d.c. four-probe technique using new semiautomatic equip ment. The sample voltage was measured automatically every 10 or 20 s with an accuracy to f 1 uV. The sample was warmed up very slowly so that the temperature change occurring during each measurement, which usually required about 15 s, was negligible (0.1-0.2 K). The temperature was measured 0022-5088/83/0000-0000/$03.00
0 Elsevier Sequoia/Printed
in The Netherlands
L46
using an (Au-0.7%Fe)-chrome1 thermocouple with an accuracy to f 0.05 K. The reproducibility of the results was better than 1%. 3. Results and discussion The temperature dependence of the electrical resistivity of US in two crystallographic directions ([loo] and [llO]) is shown in Fig. 1. Although the shapes of the two curves are similar, showing a typical knee at T,, the resistivity values are rather different. The correct Curie temperature was determined at the point where the derivative dp/dT was a maximum. The experimental Curie temperature is the same for both samples within the limits of experimental error and is 174+ 1 K (see the insets to Fig. 1). This temperature is appreciably lower than that of 180 K estimated in other electrical measurements [l-7]. Nevertheless our value is in good agreement with those determined from magnetic measurements on US single crystals [lo, 111. A computer fit showed that the resistivity at low temperatures could be described by p(T) = p,, +AT’
(1)
The fit was made for the temperature ranges 4.2-50 K and 4.2-130 K. The results are given in Table 1 and Fig. 2. It can be seen in Table 1 that the least-squares error is somewhat lower for the former temperature range which shows a better linear behaviour than that of the latter range. In general the values of A obtained in this work in the temperature range 4.2-130 K, which are also given in Table 1, lie between those given by Schoenes et al. [7] and Matsui et al. [5] which are 4.5 x 10e3 fl cm Km2and 5.18 x 10e3 @2 cm Ke2 respectively. The residual resistivity p0 is sample dependent and ranges from 35 to 45 fl cm in good agreement with the results reported earlier [5,7]. 150
200
250
300
[KI
250
0'
50
100
150 _ lb,, I InI
200 3180190 ' " '+ - 160 171 -? ilKI
Fig. 1. p vs. Tfor single-crystal US samples oriented in the [NO] and [llO] directions. show the derivative dp/dTin the neighbourhood of the critical transition.
The insets
TABLE
1
The electrical
characteristics
of US PO W cm)
Sample
CIW”Sb CW”Sb
174+_1 174+_1 9180
US single crystal’ US polycrystal “The “This c Ref. dRef. ‘This
179.8kO.6
A”(x10-3flcmK-2)
PIllas W cm)
B’ (IIQ cm K-V
4.2-50 K
4.2-130 K
46 39 20-45
5.60(2) 5.77(l) -
5.00(5) 4.90(10) 4.5
148 124
0.166(l) 0.194(5) -
34
-
5.18’
-
-
numbers in parentheses are the least-squares errors. work. 7. 5. value was obtained in the temperature range 4.2-167 K. 50
75
100
125
150
175
TLK
125
30
Fig. 2. p-p0
vs. 2” curve for [NO],,:
-,
x103
this work; ---,
ref. 7.
The TZ dependence obtained for the resistivity at low temperatures is similar to the temperature dependence of the magnetization [lo] and it can be expressed in terms of electron-magnon scattering according to the equation P,,_
(2)
with the magnon energy at the centre of the Brillouin zone (q = 0) equal to zero.
L48
This unusual behaviour may also explain the absence of sharp magnon branches in the inelastic neutron scattering experiment reported in ref. 12. In agreement with earlier work the resistivity of US is almost linearly dependent on temperature from T, to at least 800 K [4] and therefore it can be expressed as p(T) =
PO + A,&)
+ BT
(3)
The values of P,,,(W) for our two samples are also given in Table 1 and it can be seen that they are slightly different. However, the lattice constants, the Curie temperatures and other quantities measured for US all appear to be strongly sample dependent, probably because of the variations in sample purity and stoichiometry which are likely to have a marked influence on the band structure.
1 2 3 4 5 6 7 8 9 10 11 12
M. A. Karter and C. W. Kazmierowicz, J. Appl. Phys., 35(1964) 1053. H. Furuya, J. Appl. Phys., 7(1968) 779. M. Allbutt, R. M. Dell, A. R. Junkison and I. A. Marples, J. Inorg. Nucl. Chem., 32 (1970) 2159. M. Kamimoto, Y. Takahashi and T. Mukaibo, J. Phys. Chem. Solids, 37(1976) 719. H. Matsui, S. Wakashima, K. Katori, M. Tamaki and T. Kirihara, J. Nucl. Muter., 110 (1982) 208. H. Matsui, T. Kirihara and S. Nasu, J. Nucl. Muter., 56(1975) 365. J. Schoenes, C. Travaglini, 0. Vogt and P. Wachter, Physica B, 102(1980) 308. W. Trzebiatowski and T. Palewski, Bull. Acad. Pol. Sci., Ser. Sci. Chim., 19(1971) 83. 0. L. Kruger and J. B. Moser, J. Phys. Chem. Solids, 28 (1967) 2321. D. L. Tillwick and P. de V. du Plessis, J. Mugn. Magn. Muter., 3 (1976) 319. A, T. Aldred and R. Trot, J. Magn. Magn. Mater., to be published. T. M. Holden, W. J. L. Buyers, E. C. Svensson, J. A. Jackman, A. F. Murray, 0. Vogt and P. de V. du Plessis, J. Appl. Phys., 53(1982) 1967.
of the Less-Common
Metals,
90(1983)
L45-L48
L45
Letter Electrical resistivity of uranium monosulphide
R. TROC and L. KRAWCZYK Institute for Low Temperature and Structure Research, Polish Academy of Sciences, 50950 Wrodaw (Poland) (Received February 1,1983)
Introduction The electrical properties of uranium monosulphide (US) which is a ferromagnet at temperatures below about 180 K have been investigated by many workers. Most of these investigations were performed using sintered samples. The earliest measurements of the electrical resistivity of US were made below room temperature Cl-53 and at high temperatures up to 1500 “C [5,6]. Electrical resistivity data for US single crystals have recently been reported, but this information is only available in abstract form [7]. In this letter we report resistivity data for US single crystals measured as a function of temperature. The measurements were made in two directions ([loo] and [llO]) in order to detect any anisotropy in the resistivity behaviour. 1.
2. Experimental details The US was first prepared in powder form by direct reaction between the constituent elements as described in ref. 8. The polycrystalline US sample was heated in a closed tungsten crucible up to 2600 “C, i.e. about 150 “C above the melting point, and was then cooled to 2000 “C at a rate of 2 “C h- l. A fairly large single crystal was selected and several bar-shaped US samples were cut from it for the electrical measurements. An X-ray examination of the US single crystal using the Bond technique gave a value of 5.4847 fO.OOO1 A for the lattice constant. This value is close to that obtained by Kruger and Moser [9] and represents the lower limit of a wide range of lattice constants reported for US in the literature (see, for example, ref. 10). The quality of the single crystal obtained was rather high, as was shown by the fact that the X-ray linewidth was 10’. The electrical resistivity in the temperature range 4.2-300 K was measured by a standard d.c. four-probe technique using new semiautomatic equip ment. The sample voltage was measured automatically every 10 or 20 s with an accuracy to f 1 uV. The sample was warmed up very slowly so that the temperature change occurring during each measurement, which usually required about 15 s, was negligible (0.1-0.2 K). The temperature was measured 0022-5088/83/0000-0000/$03.00
0 Elsevier Sequoia/Printed
in The Netherlands
L46
using an (Au-0.7%Fe)-chrome1 thermocouple with an accuracy to f 0.05 K. The reproducibility of the results was better than 1%. 3. Results and discussion The temperature dependence of the electrical resistivity of US in two crystallographic directions ([loo] and [llO]) is shown in Fig. 1. Although the shapes of the two curves are similar, showing a typical knee at T,, the resistivity values are rather different. The correct Curie temperature was determined at the point where the derivative dp/dT was a maximum. The experimental Curie temperature is the same for both samples within the limits of experimental error and is 174+ 1 K (see the insets to Fig. 1). This temperature is appreciably lower than that of 180 K estimated in other electrical measurements [l-7]. Nevertheless our value is in good agreement with those determined from magnetic measurements on US single crystals [lo, 111. A computer fit showed that the resistivity at low temperatures could be described by p(T) = p,, +AT’
(1)
The fit was made for the temperature ranges 4.2-50 K and 4.2-130 K. The results are given in Table 1 and Fig. 2. It can be seen in Table 1 that the least-squares error is somewhat lower for the former temperature range which shows a better linear behaviour than that of the latter range. In general the values of A obtained in this work in the temperature range 4.2-130 K, which are also given in Table 1, lie between those given by Schoenes et al. [7] and Matsui et al. [5] which are 4.5 x 10e3 fl cm Km2and 5.18 x 10e3 @2 cm Ke2 respectively. The residual resistivity p0 is sample dependent and ranges from 35 to 45 fl cm in good agreement with the results reported earlier [5,7]. 150
200
250
300
[KI
250
0'
50
100
150 _ lb,, I InI
200 3180190 ' " '+ - 160 171 -? ilKI
Fig. 1. p vs. Tfor single-crystal US samples oriented in the [NO] and [llO] directions. show the derivative dp/dTin the neighbourhood of the critical transition.
The insets
TABLE
1
The electrical
characteristics
of US PO W cm)
Sample
CIW”Sb CW”Sb
174+_1 174+_1 9180
US single crystal’ US polycrystal “The “This c Ref. dRef. ‘This
179.8kO.6
A”(x10-3flcmK-2)
PIllas W cm)
B’ (IIQ cm K-V
4.2-50 K
4.2-130 K
46 39 20-45
5.60(2) 5.77(l) -
5.00(5) 4.90(10) 4.5
148 124
0.166(l) 0.194(5) -
34
-
5.18’
-
-
numbers in parentheses are the least-squares errors. work. 7. 5. value was obtained in the temperature range 4.2-167 K. 50
75
100
125
150
175
TLK
125
30
Fig. 2. p-p0
vs. 2” curve for [NO],,:
-,
x103
this work; ---,
ref. 7.
The TZ dependence obtained for the resistivity at low temperatures is similar to the temperature dependence of the magnetization [lo] and it can be expressed in terms of electron-magnon scattering according to the equation P,,_
(2)
with the magnon energy at the centre of the Brillouin zone (q = 0) equal to zero.
L48
This unusual behaviour may also explain the absence of sharp magnon branches in the inelastic neutron scattering experiment reported in ref. 12. In agreement with earlier work the resistivity of US is almost linearly dependent on temperature from T, to at least 800 K [4] and therefore it can be expressed as p(T) =
PO + A,&)
+ BT
(3)
The values of P,,,(W) for our two samples are also given in Table 1 and it can be seen that they are slightly different. However, the lattice constants, the Curie temperatures and other quantities measured for US all appear to be strongly sample dependent, probably because of the variations in sample purity and stoichiometry which are likely to have a marked influence on the band structure.
1 2 3 4 5 6 7 8 9 10 11 12
M. A. Karter and C. W. Kazmierowicz, J. Appl. Phys., 35(1964) 1053. H. Furuya, J. Appl. Phys., 7(1968) 779. M. Allbutt, R. M. Dell, A. R. Junkison and I. A. Marples, J. Inorg. Nucl. Chem., 32 (1970) 2159. M. Kamimoto, Y. Takahashi and T. Mukaibo, J. Phys. Chem. Solids, 37(1976) 719. H. Matsui, S. Wakashima, K. Katori, M. Tamaki and T. Kirihara, J. Nucl. Muter., 110 (1982) 208. H. Matsui, T. Kirihara and S. Nasu, J. Nucl. Muter., 56(1975) 365. J. Schoenes, C. Travaglini, 0. Vogt and P. Wachter, Physica B, 102(1980) 308. W. Trzebiatowski and T. Palewski, Bull. Acad. Pol. Sci., Ser. Sci. Chim., 19(1971) 83. 0. L. Kruger and J. B. Moser, J. Phys. Chem. Solids, 28 (1967) 2321. D. L. Tillwick and P. de V. du Plessis, J. Mugn. Magn. Muter., 3 (1976) 319. A, T. Aldred and R. Trot, J. Magn. Magn. Mater., to be published. T. M. Holden, W. J. L. Buyers, E. C. Svensson, J. A. Jackman, A. F. Murray, 0. Vogt and P. de V. du Plessis, J. Appl. Phys., 53(1982) 1967.