Magnetic Contribution to Heat Capacity and Entropy of Nicke Ferrite (NiFe2O4)

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The heat capacity of nickel ferrite was measured as a function of temperature over the range from 50 to 1200 C using a differential scanning calorimeter. A thermal anomaly was observed at 584.9 C, the expected Curie temperature, T{sub c}. The observed behavior was interpreted by recognizing the sum of three contributions: (1) lattice (vibrational), (2) a spin wave (magnetic) component and (3) a {lambda}-transition (antiferromagnetic-paramagnetic transition) at the Curie temperature. The first was modeled using vibrational frequencies derived from an experimentally-based ir absorption spectrum, while the second was modeled using a spin wave analysis that provided a T{sup 3/2} ... continued below

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S Ziemniak, L Anovitz, R Castelli December 15, 2005.

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The heat capacity of nickel ferrite was measured as a function of temperature over the range from 50 to 1200 C using a differential scanning calorimeter. A thermal anomaly was observed at 584.9 C, the expected Curie temperature, T{sub c}. The observed behavior was interpreted by recognizing the sum of three contributions: (1) lattice (vibrational), (2) a spin wave (magnetic) component and (3) a {lambda}-transition (antiferromagnetic-paramagnetic transition) at the Curie temperature. The first was modeled using vibrational frequencies derived from an experimentally-based ir absorption spectrum, while the second was modeled using a spin wave analysis that provided a T{sup 3/2} dependency in the low temperature limit, but incorporated an exchange interaction between cation spins in the octahedral and tetrahedral sites at elevated temperatures, as first suggested by Grimes [15]. The {lambda}-transition was fitted to an Inden-type model which consisted of two truncated power law series in dimensionless temperature (T/T{sub c}). Exponential equality was observed below and above T{sub c}, indicating symmetry about the Curie temperature. Application of the methodology to existing heat capacity data for other transition metal ferrites (AFe{sub 2}O{sub 4}, A = Fe, Co) revealed the same exponential equality, i.e., m = n = 5.

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  • Report No.: LM-05K177
  • Grant Number: DE-AC12-00SN39357
  • Office of Scientific & Technical Information Report Number: 875901
  • Archival Resource Key: ark:/67531/metadc878242

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  • December 15, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Feb. 16, 2017, 6:46 p.m.

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S Ziemniak, L Anovitz, R Castelli. Magnetic Contribution to Heat Capacity and Entropy of Nicke Ferrite (NiFe2O4), article, December 15, 2005; Niskayuna, NY. (digital.library.unt.edu/ark:/67531/metadc878242/: accessed December 10, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.