Accession Number : AD0015523


Title :   MAGNETIC AND ELECTRIC PROPERTIES OF MAGNETITE AT LOW TEMPERATURES


Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INSULATION RESEARCH


Personal Author(s) : Calhoun, B A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/015523.pdf


Report Date : Jul 1953


Pagination or Media Count : 27


Abstract : The low-temperature transition in magnetite was studied by x-ray analysis and by electric and magnetic means. The orthorhombic structure of magnetite below the transition was considered confirmed by experimental evidence. Direct determination of the unit cell size by x-ray and strain-gage measurements showed that the orthorhombic axes are oriented so that (1) the c axis lies along one of the original cube edges, and (2) the a and b axes lie along the face diagonals normal to the c axis. Corroborative evidence of the orthorhombic structure was obtained from a determination of the magnetic anisotropy energy (the difference between the energies required to magnetize a sample in an arbitrary direction and in the direction of easy magnetization). The anisotropy of the conductivity agreed with that expected from Verwey's ordered structure (J. Chem. Phys. 15:181, 1947). Verwey's model was considered to explain the influence of a magnetic field applied during cooling on the properties of the crystal below the transition. The twinning which occurred at the transition complicated the magnetic behavior at low temperatures. The increase in conductivity anisotropy with decreasing temperature appeared directly related to the increase in long-range order. (See also AD6192)


Descriptors :   *MAGNETITE , *ELECTRICAL PROPERTIES , *MAGNETIC PROPERTIES , X RAYS , ELECTRICAL CONDUCTIVITY , LONG RANGE(DISTANCE) , ANISOTROPY , STRAIN GAGES , TRANSITIONS , MAGNETIZATION , CRYOGENICS , SIZES(DIMENSIONS) , MAGNETIC FIELDS , MEASUREMENT , LOW TEMPERATURE


Subject Categories : Electricity and Magnetism


Distribution Statement : APPROVED FOR PUBLIC RELEASE