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Title: Heat capacities, order-disorder transitions, and thermodynamic properties of rare-earth orthoferrites and rare-earth iron garnets

Rare-earth orthoferrites, RFeO{sub 3}, and rare-earth iron garnets (RIGs) R{sub 3}Fe{sub 5}O{sub 12} (R=rare-earth elements) were prepared by citrate-nitrate gel combustion method and characterized by X-ray diffraction method. Isobaric molar heat capacities of these oxides were determined by using differential scanning calorimetry from 130 to 860 K. Order-disorder transition temperatures were determined from the heat capacity measurements. The Neel temperatures (T{sub N}) due to antiferromagentic to paramagnetic transitions in orthoferrites and the Curie temperatures (T{sub C}) due to ferrimagnetic to paramagnetic transitions in garnets were determined from the heat capacity data. Both T{sub N} and T{sub C} systematically decrease with increasing atomic number of R across the series. Lattice, electronic and magnetic contributions to the total heat capacity were calculated. Debye temperatures as a function of absolute temperature were calculated for these compounds. Thermodynamic functions like C{sub p,m}{sup o}, S{sub m}{sup o}, H{sup o}, G{sup o}, (H{sub T}{sup o}-H{sub 0}{sup o}), (H{sub T}{sup o}-H{sub 298.15K}{sup o}), -(G{sub T}{sup o}-H{sub 298.15K}{sup o})/T, {delta}{sub f}H{sub m}{sup o}, and {delta}{sub f}G{sub m}{sup o} have been generated for the compounds RFeO{sub 3}(s) and R{sub 3}Fe{sub 5}O{sub 12}(s) based on the experimental data obtained in this study and the available data in the literature. -more » Graphical abstract: Plot of molar heat capacities (C{sub p,m}{sup o}) of R{sub 3}Fe{sub 5}O{sub 12}(s) (R=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) against temperature (T). The inset shows the magnified portion of the heat capacity plot near the transition region indicating nearly same values of Curie temperatures for different R{sub 3}Fe{sub 5}O{sub 12}(s)« less
Authors:
 [1] ; ;  [2]
  1. Product Development Section, Radiochemistry and Isotope Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India), E-mail: sureshp@barc.gov.in
  2. Product Development Section, Radiochemistry and Isotope Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)
Publication Date:
OSTI Identifier:
21043866
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 181; Journal Issue: 1; Other Information: DOI: 10.1016/j.jssc.2007.11.003; PII: S0022-4596(07)00452-5; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CALORIMETRY; COMBUSTION; CURIE POINT; DEBYE TEMPERATURE; DYSPROSIUM COMPOUNDS; ERBIUM COMPOUNDS; EUROPIUM COMPOUNDS; FERRITE GARNETS; GADOLINIUM COMPOUNDS; HOLMIUM COMPOUNDS; LUTETIUM COMPOUNDS; NEEL TEMPERATURE; ORDER-DISORDER TRANSFORMATIONS; PARAMAGNETISM; SAMARIUM COMPOUNDS; SPECIFIC HEAT; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; TERBIUM COMPOUNDS; THULIUM COMPOUNDS; X-RAY DIFFRACTION; YTTERBIUM COMPOUNDS