Geochem Geophys Geosyst
April 2018
Recent sophisticated global data compilations and magnetic surveys have been used to investigate the nature of magnetization in the lower crust and upper mantle. Two approaches to constraining magnetizations are developed, providing minimum (0.01 SI) and maximum (0.
View Article and Find Full Text PDFMagnetic measurements are routinely used in geophysics and environmental sciences to obtain detailed information about concentrations and quality of iron minerals. Here, magnetic properties of 38 terrestrial moss samples (Hylocomium splendens) from a ~120km south-north transect through Oslo are studied to gain better insight into the nature and origin of their Fe fraction. The concentration-dependent quantities, magnetic susceptibility k, and isothermal remanent magnetization IRM(700mT) after weight normalization have significantly higher values in urban regions, and parallel the previously found concentration signals of 16 out of 29 chemical elements (Ag, Al, Au, Bi, Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb, Pt, Sb, Ti, and Zn).
View Article and Find Full Text PDFMagnetic exchange bias is a phenomenon whereby the hysteresis loop of a 'soft' magnetic phase is shifted by an amount H(E) along the applied field axis owing to its interaction with a 'hard' magnetic phase. Since the discovery of exchange bias fifty years ago, the development of a general theory has been hampered by the uncertain nature of the interfaces between the hard and soft phases, commonly between an antiferromagnetic phase and a ferro- or ferrimagnetic phase. Exchange bias continues to be the subject of investigation because of its technological applications and because it is now possible to manipulate magnetic materials at the nanoscale.
View Article and Find Full Text PDFMagnetic anomalies associated with slowly cooled igneous and metamorphic rocks are commonly attributed to the presence of the mineral magnetite. Although the intermediate members of the ilmenite-haematite mineral series can also carry a strong ferrimagnetic remanence, it is preserved only in rapidly cooled volcanic rocks, where formation of intergrowths of weakly magnetic haematite and paramagnetic ilmenite is suppressed. But the occurrence of unusually large and stable magnetic remanence in rocks containing such intergrowths has been known for decades, and has recently been the subject of intense investigation.
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