SPECIFIC HEAT OF PRASEODYMIUM AND NEODYMIUM METALS BETWEEN 0.4 AND 4 K
The specific heat C/sub p/ of praseodymium and neodymium metals was measured between 0.4 and 4 deg K in a He/sup 3/ cryostat. After assuming, on the basis of earlier research, C/sub L/ == 0.554T/sup 3/ (specific heat always given in mJ/mole deg K) and C/sub E/ - 10.5T for the lattice and electronic specific heats of praseodymium, the remaining C/sub p/ was analyzed into a nuclear contribution C/sub N/ = 20.9T/sup -2/ and into a magnetic contribution C/sub M/. If compared with Bleaney's calculations based on fully magnetized electronic states in the metal, the experimental C/sub N/ shows that 2.0% of the sample was in a cooperative state, probably ferromagnetic, the rest of the metal being paramagnetic. C/sub M/ was further separated into a Schottky contribution with an excited electronic level at 28 deg K and into a smeared-out cooperative peak with a maximum at 3.2 deg K. The entropy under the latter curve is 95 mJ/mole deg K as compared with the value 0.020 x R ln2 == 115 mJ/mole deg K that would be expected as a result of magnetic ordering in 2.0% of the sample. Both C/sub N/ and C/sub M/ thus suggest that 2% of the sample enters a cooperative phase below 3.2 deg K. This mechanism to explain C/sub N/ and C/sub M/ must be considered as preliminary. The value of C/sub N/ is rather different from earlier results. A sample-dependent C/sub N/ is consistent with the picture of ferromagnetic domains. Below 2 deg K the specific heat of praseodymium can be written, with 1% accuracy, C/sub p/ = 4.53T9 + 24.4T + 20.9T/sup -2/. At higher temperatures C/sub p/ cannot be represented by a simple power series. The magnetic contribution to the specific heat of neodymium is huge due to cooperative peaks at 7 and 19 deg K; even at 1 deg K C/sub M/ represents 88% of the total C/sub p/. Below 7 deg K neodymium is antiferromagnetic. After adopting C/sub L/ = )T/sup -2/. This value is about 50% smaller than that calculated by Bleaney if full electronic magnetization is assumed. However, the splitting of the electronic levels is rather large in neodymium and one cannot assume that (J/sub z/) in a cooperative state tends to J = 9/2, but rather reaches a lower limiting value at T = 0 deg K. This explains the smaller experimental C/sub N/. Between 0.4 and 1 deg K the specific heat of neodymium may be written with 1% accuracy C/sub p/ = 125.7T/sup 3/ + 22.5T + 6.4T/sup -2/. The accuracy of these measurements is estimated as 1.5% at 0.4 deg K and as 0.5% between 1 and 4 deg K. While checking the performance of the cryostat the specific heat of copper was found to be C/sub p/ = 0.0510T/sup 3/) + 0.698T. (auth)
- Research Organization:
- Argonne National Lab., Ill.
- NSA Number:
- NSA-18-006114
- OSTI ID:
- 4150682
- Journal Information:
- Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 133; ISSN PHRVA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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