Magnetic anisotropy behaviour of pyrrhotite as determined by low- and high-field experiments

Details Magnetic anisotropy behaviour of pyrrhotite as determined by low- and high-field experiments Magnetic anisotropy behaviour of pyrrhotite as determined by low- and high-field experiments

Jul 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008geoji.174...42m&link_type=abstract

Geophysical Journal International, Volume 174, Issue 1, pp. 42-54.

Astronomy and Astrophysics

Astronomy

3

Magnetic And Electrical Properties, Magnetic Fabrics And Anisotropy, Magnetic Mineralogy And Petrology, Rock And Mineral Magnetism

Scientific paper

Here we report on the sources of magnetic anisotropy in pyrrhotite, an iron sulphide present in many rocks as an important carrier of the Natural Remanent Magnetization. While the magnetic hysteresis parameters of pyrrhotite are well known, the existing database concerning its anisotropy behaviour is patchy and ambiguous. Therefore, a collection of 11 seemingly single crystals of natural pyrrhotite was scrutinized. Before embarking on the anisotropy determinations the set of single crystals was extensively characterized rock magnetically by measuring Curie temperatures, hysteresis loops, IRM acquisition curves, and FORC diagrams (the latter three all at room temperature). First the variation of the low-field susceptibility as function of applied field and grain size was evaluated for fields ranging from 1 to 450 A m-1. Existing grain size dependent data and the present larger crystals show a logarithmic grain size dependence. This enables estimating the grain size for unimodal pyrrhotite distributions in rocks. Measured trends are better fitted with an exponential function than with a Rayleigh Law style function. Based on the rock magnetic characterization and the behaviour of the anisotropy of magnetic susceptibility six samples (of the original 11) were selected for the high-field anisotropy determinations within the basal plane. Those data were acquired with a torque cantilever-type magnetometer. As expected, most single crystals showed a pure 6-θ curve within their basal plane because of the easy axis configuration. In some crystals, however, lower harmonic terms overlapped the 6-θ term. This may be the dominant source of the observed variation in magnetic anisotropy properties. Torque data of three of the six samples were of sufficient quality to allow evaluation of K1. Re-evaluation of existing torque data and including the present newly derived determinations, yields for the anisotropy constant of pyrrhotite within the basal plane K1: (2.7 +/- 0.2) 104 Jm-3. This is over an order of magnitude more precise than the sparse existing K1 data; only the value reported by Mikami and co-authors in 1959 agrees with the new determination. With this firmly established K1 value meaningful anisotropy models are now possible for pyrrhotite-bearing rocks.

Affiliated with

Also associated with

No associations

Rating

Magnetic anisotropy behaviour of pyrrhotite as determined by low- and high-field experiments does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Magnetic anisotropy behaviour of pyrrhotite as determined by low- and high-field experiments, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic anisotropy behaviour of pyrrhotite as determined by low- and high-field experiments will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1317818