JournalofLow TemperaturePhysics, Vol,5, No. 4, 1971
The Resistivity of fl-Manganese and Nickel-Stabilized Alloys* K. C. Whittaker, P. A. Dziwornooh, and R. J. Riggs Physics Department, University o f Science and Technology, Kumasi, Ghana (Received May 18, 1971)
Resistivity-temperature measurements have been carried out on pure manganese metal in which the fl phase had been retained by quenching, and on two alloys in which the fl phase was found to be stabilized at room temperature. The resistivity of flmanganese is seen to decrease monotonically with temperature and no anomaly is revealed in the temperature range 4.2-7 K. A low-temperature resistance minimum, however, appears in the nickel-stabilized alloys. 1. I N T R O D U C T I O N The present work was part of our study of manganese. Essentially, no data exist on the fl form of manganese which is stable between 710 and 1079 C. This modification has a complex cubic structure (A13) 1'2 and was found to be very brittle. Experiments were carried out on pure manganese metal in which the fl phase had been retained by quenching, and on two alloys in which the fl phase was found to be stabilized at room temperature by the addition of 3 and 5 % nickel. Measurements were made between 2 and 273 K.
2. Q U E N C H E D /3-MANGANESE Method. Several attempts to quench fl-manganese from 900 C in ice-cooled water failed. The fl-manganese used in our experiments was quenched in a bath of liquid nitrogen. Specimens were first cut by spark erosion from pieces of manganese flake of 99.995 % purity. After degassing for some hours at 600 C they were sealed into a silica capsule, which was then heated to about 1200 C. The capsule was then maintained somewhat below this temperature for 1 h and then ejected into the nitrogen bath. The thermal shock was sufficient to cause the capsule to shatter, thus bringing the specimen into almost immediate contact with the liquid nitrogen. *The work reported here formed part of a Ph.D. thesis submitted at the University of Oxford by one of us, the late K. C. Whittaker, Professor of Physics, University of Science and Technology, Kumasi, Ghana. © 1971 Plenum Publishing Corporation, 227 West 17th Street, New York, N.Y. 10011. 461
K. C. Whittaker,P. A. Dziwornooh,and R. J. Riggs
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After quenching the sample was warmed up to room temperature without undergoing a phase change into the c~ form. Indeed, x-ray examination showed no trace of any phase other than the/3 phase• The same cryostat and experimental technique was employed as in the preceding paper] About 150 experimental points were obtained between 2 and 273 K. The temperature measurements, made with an iron + 0.3 % gold-chromel P thermocouple, were accurate to about 0.1 K, and the normalized resistivities are accurate to 0.1% or better• R e s u l t s . The resistivity curve is shown in Fig. 1, and some details are listed in Table I. The resistivity of/3-manganese can be seen to decrease monotonically with temperature, and is still decreasing at 2 K. Our results did not reveal any anomaly in the resistivity in the temperature region 4.2-7 K, although a specific heat anomaly has been reported) It has been suggested that short-range magnetic ordering is the cause. 4
1.0
I
I
I
I
R R273
°....°.. '°
/
,." / J
•. •"
5*/, Ni
J
/J
• ° .•"
0.9
I
J
'~"
.'"
/
// //
I~-Mn
//
/I
0.8
/2
/
/
3*/, Ni
//
//
0.7
/
/
//
//
//
/
//
////
11
0-6
I
I 100
I
I 200
300*K
Fig. 1. Resistivity of fl-Mn and nickel-stabilizedalloys.
The Resistivity of lI-Manganese and Nickel-Stabilized Alloys
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TABLE I Approximate behavior of R r - R o Sample
/~-Mn 3 % Ni 5 % Ni
Ro/R273
0.602 0.631 0.877
c%73, 10-* K - I
7.5 19 4.7
Train, K
-13 44
Rrnln/R273
0.633 0.864
Low temperature
Intermediate temperature
T1-6 ( T < 15K) Irregular Irregular
T ° 6 ( T > 50K) 50 K) Linear (T > 100 K)
TI'I(T >
The absolute value of the resistivity at 273 K was found to be 252/~.cm, and at 83 K was 198 #O.cm. However, because the material is very brittle and must be quenched so severely, the possibility of internal cracking makes the form factor uncertain. The results can be compared only with that of Brunke, 5 who obtained P273 91 #~.cm, and Reddeman, 6 who obtained ,0273 = 140 #U~.cm and P83 = 1 0 0 #~'~.cm. P273 - - Po was found to be 111 #f].cm but, because of the high value of PO/P273, the applicability of Matthiesen's rule is doubtful. :
3. NICKEL-STABILIZED ALLOYS These alloys with 3 and 5 % nickel were prepared together with those of lower percentage, but unlike the latter proved to be in the/3 phase. The samples were prepared by melting the components on a slab of magnesia in an induction furnace. X-ray analysis showed the 3 % specimen to be predominantly, and the 5 % specimen completely, in the/~ phase. Results. The resistivity curves are shown in Fig. 1, and some details listed in Table I. The general shape of the resistivity curves is similar to that of the quenched pure form. However, there are wide differences in the temperature coefficients ~273, and a low-temperature resistance minimum has appeared in both alloys. In the 3 % sample a definite step of about 4 % of the absolute value occurred at 6.5 K. This anomaly was checked carefully and proved to be reproducible. It is thought that it may be connected with the specific heat anomaly mentioned above. ACKNOWLEDGMENTS We are grateful to Dr. K. Mendelssohn, F.R.S., for suggesting, guiding, and supervising the work and also for several helpful discussions, and to Drs. G. Garton, D. A. Hukin, and I. F. Bowers for help and advice in the preparation of specimens. REFERENCES 1. A. Westgren and G. Phragmen, Z. Physik 33, 777 (1925). 2. G. D. Preson, Phil. Mag. 5, 1207 (1928).
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3. 4. 5. 6. 7.
K. C. Whittaker, P. A. Dziwornooh, and R. J. Riggs
S. Shinozaki, A. Arrott, H. Sato, and J. E. Zimmerman, Bull. Am. Phys. Soc. 8, 66 (1963). Y. Masuda, K. Asayama, S. Kobayashi, and J. Itoh, J. Phys. Soc. Japan 19, 460 (1964). F. Brunke, Ann. Physik 21, 139 (1934). H. Reddeman, Ann. Physik 22, 28 (1935). K. C. Whittaker and P. A. Dziwornooh, J. Low Temp. Phys. 5, 447 (1971).
