THE LOW-TEMPERATURE TRANSITION IN MAGNETITE
MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INSULATION RESEARCH
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Magnetite was shown to transform from the cubic to the orthorhombic system at temperatures below 119 deg K. The thermal expansion coefficient of the c axis became negative below 119 deg K, and at about 95 deg K there was no appreciable difference in the spacing of 440 and 008. The dimensions of the magnetite unit cell were measured at 295 deg, 128 deg, and 78 deg K and the resulting volumes were 591.4, 589.1, and 589.6 A to the power of 3, respectively. From these data and the c-axis length at 108 deg K, the coefficients of thermal expansion above and below the transition were calculated.
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