Revisiting the mechanism of reversed thermoremanent magnetization based on observations from synthetic ferrian ilmenite (y = 0.7)

France Lagroix (1) , Subir K. K. Banerjee (1) , Bruce . M. Moskowitz (1)

1 Institute for Rock Magnetism, Newton Horace Winchell School of Earth Sciences [Minneapolis]

This study investigates the magnetic behavior of three well-characterized synthetic single-phase ferrian ilmenite (y = 0.7) specimens over the temperature range between 10 K and 573 K. Careful experiments measuring induced and remanent magnetizations in variable temperatures, applied magnetic fields, and pretreatment conditions are conducted in order to elucidate the mechanism leading to reversed thermoremanent magnetization (RTRM). Magnetic ordering temperatures of the cation ordered domains, in all three samples, are estimated at 380 K, suggesting that their Curie temperatures (T C) are independent of the sample's thermal history. This is not the case for cation disordered boundaries resulting from quenching from high temperatures. These cation disordered domains have estimated magnetic ordering temperatures of 418 K (Q1300), 410 K (Q1050), and 425 K (Q900). The data unambiguously support a less than perfect ferrimagnetic–antiferromagnetic exchange interaction as the fundamental source of RTRM. Furthermore, the magnetic field strength of the ''effective'' exchange anisotropies in such polycrystalline samples are estimated at $2.7 mT (Q1300), $12 mT (Q1050), and 0 mT (Q900). However, from the results presented herein we conclude that favorable conditions for the acquisition of RTRM are dependent not only on the strength of the exchange anisotropy but also on the crucial role played by the size of the cation ordered domains. INDEX TERMS: 1519 Geomagnetism and Paleomagnetism: Magnetic mineralogy and petrology; 1540 Geomagnetism and Paleomagnetism: Rock and mineral magnetism; 1714 History of Geophysics: Geomagnetism and paleomagnetism; KEYWORDS: ferrian ilmenite, reversed thermoremanent magnetization, exchange anisotropy Citation: Lagroix, F., S. K. Banerjee, and B. M. Moskowitz (2004), Revisiting the mechanism of reversed thermoremanent magnetization based on observations from synthetic ferrian ilmenite (y = 0.7),

Domaines: Géophysique [physics.geo-ph]

France Lagroix, Subir K. K. Banerjee, Bruce . M. Moskowitz. Revisiting the mechanism of reversed thermoremanent magnetization based on observations from synthetic ferrian ilmenite (y = 0.7). Journal of Geophysical Research : Solid Earth, 2004, 109 (B12), pp.B12108. ⟨10.1029/2004JB003076⟩. ⟨insu-01351587⟩