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Title: Magnetic Contribution to heat capacity and entropy of nickel ferrite

Abstract

The heat capacity of nickel ferrite was measured as a function of temperature from 50 to 1200 C using a differential scanning calorimeter. A thermal anomaly was observed at 584.9 C, the expected Curie temperature, TC. The observed behavior was interpreted by recognizing the sum of three contributions: (1) lattice (vibrational), (2) a spin wave (magnetic) component and (3) a ?-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 T3/2 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 ?-transition was fitted to an Inden-type model which consisted of two truncated power law series in dimensionless temperature (T/TC). Exponential equality (m=n=7) was observed below and above TC, indicating symmetry about the Curie temperature. Application of the methodology to existing heat capacity data for other transition metal ferrites (AFe2O4, A=Fe, Co) revealed nearly the same exponential equality, i.e., m=n=5.

Authors:
 [1];  [1];  [2]
  1. Lockheed Martin Corporation
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
Work for Others (WFO)
OSTI Identifier:
1003699
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Journal of Physics and Chemistry of Solids
Additional Journal Information:
Journal Volume: 4582; Journal Issue: 10.1016; Journal ID: ISSN 0022-3697
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ABSORPTION; CATIONS; CURIE POINT; ENTROPY; EXCHANGE INTERACTIONS; FERRITE; FERRITES; NICKEL; SPECIFIC HEAT; SPIN WAVES; SYMMETRY; TRANSITION ELEMENTS

Citation Formats

Ziemniak, S. E., Anovitz, Lawrence, Castelli, R. A., and Porter, Wallace D. Magnetic Contribution to heat capacity and entropy of nickel ferrite. United States: N. p., 2006. Web.
Ziemniak, S. E., Anovitz, Lawrence, Castelli, R. A., & Porter, Wallace D. Magnetic Contribution to heat capacity and entropy of nickel ferrite. United States.
Ziemniak, S. E., Anovitz, Lawrence, Castelli, R. A., and Porter, Wallace D. 2006. "Magnetic Contribution to heat capacity and entropy of nickel ferrite". United States.
@article{osti_1003699,
title = {Magnetic Contribution to heat capacity and entropy of nickel ferrite},
author = {Ziemniak, S. E. and Anovitz, Lawrence and Castelli, R. A. and Porter, Wallace D},
abstractNote = {The heat capacity of nickel ferrite was measured as a function of temperature from 50 to 1200 C using a differential scanning calorimeter. A thermal anomaly was observed at 584.9 C, the expected Curie temperature, TC. The observed behavior was interpreted by recognizing the sum of three contributions: (1) lattice (vibrational), (2) a spin wave (magnetic) component and (3) a ?-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 T3/2 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 ?-transition was fitted to an Inden-type model which consisted of two truncated power law series in dimensionless temperature (T/TC). Exponential equality (m=n=7) was observed below and above TC, indicating symmetry about the Curie temperature. Application of the methodology to existing heat capacity data for other transition metal ferrites (AFe2O4, A=Fe, Co) revealed nearly the same exponential equality, i.e., m=n=5.},
doi = {},
url = {https://www.osti.gov/biblio/1003699}, journal = {Journal of Physics and Chemistry of Solids},
issn = {0022-3697},
number = 10.1016,
volume = 4582,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}