Low-temperature specific heat of antiferromagnetic EuNi{sub 5}P{sub 3} and mixed-valent EuNi{sub 2}P{sub 2} in magnetic fields to 7 T
- Materials Sciences Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720 (United States)
The specific heats of EuNi{sub 5}P{sub 3}, an antiferromagnet, and EuNi{sub 2}P{sub 2}, a mixed-valence compound, have been measured between 0.4 and 30 K in magnetic fields of, respectively, 0, 0.5, 1, 1.5, 2.5, 5, and 7 T, and 0 and 7 T. In zero field the specific heat of EuNi{sub 5}P{sub 3} shows a {lambda}-like anomaly with a maximum at 8.3 K. With increasing field in the range 0--2.5 T, the maximum shifts to lower temperatures, as expected for an antiferromagnet. In higher fields the antiferromagnetic ordering is destroyed and the magnetic part of the specific heat approaches a Schottky anomaly that is consistent with expectations for the crystal-field/Zeeman levels. In low fields and for temperatures between 1.5 and 5 K the magnetic contribution to the specific heat is proportional to the temperature, indicating a high density of excited states with an energy dependence that is very unusual for an antiferromagnet. The entropy associated with the magnetic ordering is {similar_to}{ital R} ln8, confirming that only the Eu{sup 2+}---with {ital J}=7/2, {ital S}=7/2, {ital L}=0---orders below 30 K. In zero field approximately 20% of the entropy occurs above the Neel temperature, consistent with the usual amount of short-range order observed in antiferromagnets. The hyperfine magnetic field at the Eu nuclei in EuNi{sub 5}P{sub 3} is 33.3 T, in good agreement with a value calculated from electron-nuclear double resonance measurements. For EuNi{sub 2}P{sub 2} the specific heat is nearly field independent and shows no evidence of magnetic ordering or hyperfine fields. The coefficient of the electron contribution to the specific heat is {similar_to}100 mJ/mol K{sup 2}.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 122334
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 52, Issue 18; Other Information: PBD: 1 Nov 1995
- Country of Publication:
- United States
- Language:
- English
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