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Domain structures in single crystal magnetite below the Verwey transition as observed with a low-temperature magnetic force microscope.
K. Moloni, B. M. Moskowitz, E. D. Dahlberg
American Geophys. Union. Geophysical Research Letters 23 p. 2851 (1996).
Abstract: The magnetic domain structures on the (110) plane of magnetite (Fe/sub 3/O/sub 4/) below the Verwey transition (T/sub V/=120 K) were studied using a low-temperature magnetic force microscope (LTMFM). At 298 K, domain structures consisted of arrays of 180 degrees , 109 degrees and 71 degrees walls, typical for magnetite with cubic anisotropy. At 77 K (below T/sub V/), the cubic style patterns disappeared and transformed into uniaxial patterns consistent with the uniaxial magnetocrystalline symmetry of the low-temperature monoclinic phase of magnetite. We also observed two distinct styles of domain patterns below T/sub V/: (1) wide domains separated by straight 180 degrees walls along the in-plane 100 easy axis; and (2) intricate wavy walls with reverse spike domains characteristic of out-of-plane easy axes. This intimate mixture of domain styles within adjacent areas of the crystal reflects variations in the direction of the magnetic easy axes in different regions produced by c-axis twinning of the crystal below T/sub V/. The thermal dependence of planar and wavy-wall patterns show little change from 77 K until 110 K, where patterns disappear. Upon cooling back to 77 K, domain structures are different from the initial 77 K states, indicating that renucleation of different domain states occurs by cycling near T/sub V/. (24 References).
last modified:
10.Jun.2002
by Thomas Gredig