Stability of anhysteretic remanent magnetization in fine and coarse magnetite and maghemite particles

Johnson, H. P.; Lowrie, William; Kent, Dennis V.

Further experiments have been performed to investigate the biasing-field dependency of alternating field demagnetization curves of anhysteretic remanent magnetization as a simple test for the domain state of magnetite and maghemite particles. The biasing-field dependency in fine-grained particles was opposite to that in coarse-grained particles. The experiments were conducted on well sized synthetic specimens in the single domain, pseudo-single domain and multi-domain grain size ranges. A single domain-like biasing-field dependency was observed in equidimensional particles up to 0.2µ mean grain size and up to 0.4µ elongated grains. Either the single domain/pseudo-single domain boundary lies above at least 0.2µ grain size or this field dependency test does not distinguish between single domain and pseudo-single domain states. A multidomainlike trend was observed in very coarse magnetite. The test may possibly distinguish the change from pseudo-single domain to multi-domain states. If both fine and coarse fractions are present a confusing overlap of the demagnetization curves occurs.


Also Published In

Geophysical Journal of the Royal Astronomical Society

More About This Work

Academic Units
Lamont-Doherty Earth Observatory
Biology and Paleo Environment
Published Here
January 23, 2012