Magnetic and microstructural properties of some lodestones |
| |
Authors: | Peter J Wasilewski |
| |
Institution: | Laboratory for Extraterrestrial Physics, Astrochemistry Branch, NASA-Goddard Space Flight Center, Greenbelt, Md. 20771 U.S.A. |
| |
Abstract: | An iron ore which behaves as a permanent magnet is lodestone. The intrinsic magnetic properties and the microstructual characteristics which are responsible for the permanent-magnet properties of the lodestone have never been described or explained. Iron ores capable of being charged sufficiently strongly to behave as permanent magnets are defined here as proto-lodestones and fall into two categories — Class I which contains Fe as the only significant cation, and Class II which contains considerable Ti, Mg and Al as well. Proto-Lodestones are magnetically hardened by oxidation and precipitation processes which produce the microstructure responsible for the permanent-magnet properties. Lodestones are charged proto-lodestone iron ores. Lodestones have RH values (ratio of remanent coercive force, HR, to coercive force, HC) between 2.0 and 2.5; RI values (ratio of saturation remanence, ISR, to saturation magnetization, IS) >0.1–0.25 and the ratio of NRM/SIRM (natural remanence to saturation remanence) is 0.15–0.7. The intrinsic magnetic properties and microstructural characteristics of proto-lodestones and other iron ores are described and explained. The mechanism of charging the proto-lodestone appears to be either transient magnetic fields associated with lightning-discharge currents or presently obscure aspects of magnetization intensity enhancement associated with maghemitization of massive iron ores. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|