Elastic Constants of Iron from 4.2 to 300°K

The zero-field elastic constants of iron have been measured from 4. 2 to 300^ using the ultrasonic pulse technique. Extrapolation of the data to absolute zero gives c₁₁=2. 4310. 008, c₁₂=1. 3810. 004, and c₄₄=1. 2190. 004, all expressed in units of 10^12 dyne cm^-2. The corresponding limiting value of the Debye temperature is ₀= (4772) ^K. Using this figure, the low-temperature heat capacity data for iron have been reanalyzed assuming the presence of a spin-wave contribution to the specific heat, i. e. , the heat capacity is assumed to follow the relation C=+T^3+T^3{2}. A least squares fit of (C-{T^3) }T versus T^1{2} gives = (11. 70. 1) 10^-4 cal mole^-1 deg^-2, = (21) 10^-5 cal mole^- deg^-5{2}. There is agreement, within experimental error, between the latter figure and the theoretical estimate of =0. 810^-5 cal mole^-1 deg^-5{2} obtained from the low-temperature magnetization data of Fallot. From the room temperature elastic constants, the compressibility of iron is found to be K= (5. 950. 02) 10^-13 cm^2 dyne^-1, which agrees exactly with the static value obtained by Bridgman.