Study on Thermodynamic Properties of Fe3+-Substituted Yttrium Iron Garnets
K.B. Modia, P.K. Jha b, P.Y. Raval a, N.H. Vasoya b, K.G. Vyas a, U.M. Meshiya a, R.H. Gohil a, K.H. Jadav a, N.D. Gohil a and P.U. Sharma c
aDepartment of Physics, Saurashtra University, Rajkot 360 005, India
bDepartment of Physics, Faculty of Science, M.S. University of Baroda, Vadodara 390 002, India
cM.N. College, Visnagar 384 315, India
Received: February 22, 2016; In final form: June 28, 2016
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This paper presents the molar heat capacity at constant volume CV and characteristic Debye temperature θ, determination for the garnet system, Y3-xFe5+xO12, x=0.0, 0.1, 0.3, and 0.5 at 300 K. The θ values determined from Waldron's approach and those calculated using ultrasonic mean sound velocity, Vmo, are in agreement. CV values calculated from the Einstein theory are consistent with the reported one and theoretically expected values using the Dulong-Petit law, but Waldron's approach based on the Debye theory and the Debye T3 law fail to estimate consistent CV values. The result has been discussed in the light of key physical differences between the two theories. The applicability of the Kieffer model for molar heat capacity at constant pressure, Cp, determination has been tested. Finally, an attempt has been made to estimate electronic contribution and the temperature at which the lattice contribution and electronic contribution to the molar heat capacity become comparable.

DOI: 10.12693/APhysPolA.130.778
PACS numbers: 75.47.Lx, 05.70.-a