Magnetoacoustic emission of magnetites

Abstract

We consider the parameters of magnetoacoustic emission (MAE) in magnetites from the ores of the Urals and West Siberia. It has been shown that the differences in signals are related to various types of the domain structures of samples, whose fixity is determined by the formation conditions of magnetite and the effect of superimposed physicochemical processes. On the basis of field parameters, the magnetites have been divided into three types depending on the area of magnetic fields with MAE. These parameters can serve as the typomorphic features of magnetites of different genesis.

Magnetoacoustic emission of natural pyrrhotite

“…Magnetoacoustic emission in the magnetite of this deposit is observed at -18 to +80 kA/m, with maxima at 18-21 and 37 kA/m (Ivanchenko et al, 2012). Magnetoacoustic emission resulting from the presence of pyrrhotite is observed for these samples within a very wide interval from -129 to +245 kA/m.…”

“…3b) is determined by disseminated magnetite. Estyunino-type magnetite shows MAE at -18 to +37 kA/m, with a maximum at +9.6 kA/m (Ivanchenko et al, 2012); therefore, MAE observed at -72 to +94 kA/m, with a maximum at +11 kA/m, might be related to disseminated magnetite. Magnetoacoustic emission at -40 to +120 kA/m, with a maximum at 40 kA/m, is due to a change in the domain structure of pyrrhotite (type 4) which crystallized as prisms.…”

“…Magnetoacoustic emission was measured for cubic samples 2.4 m -3 in size on special equipment by the technique described in (Ivanchenko and Glukhikh, 2009;Ivanchenko et al, 2012). Remagnetization was carried out with the use of a magnetic field with a frequency of 0.1 Hz and an amplitude of up to 180 kA/m.…”

“…Previously, MAE within frequencies of 50-200 kHz was demonstrated in (Ivanchenko and Glukhikh, 2009;Ivanchenko et al, 2012) for magnetite and magnetite ores of different geneses. The effect of MAE within this frequency range is explained by a shift of domain boundaries with a change in the magnetic state of a sample (remagnetization by a low-frequency external magnetic field).…”

Magnetic Barkhausen Noise Measurements on Rocks

“…The magnetic characterization of a sample requires measuring various parameters such as magnetic susceptibility, magnetic hysteresis cycles, isothermal/anhysteretic remanence acquisition curves, among others. All these parameters provide essential information to identify the various ferromagnetic minerals present in a sample and their magnetic state (superparamagnetic, single-domain, pseudo-single domain, multidomain), which mainly depends on the size and shape of the grains or crystals (Dunlop & Özdemir, 1997, Ivanchenko et al, 2012.…”