Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments

作者：de Groot Lennart V^*; Fabian Karl; Bakelaar Iman A; Dekkers Mark J

来源：Nature Communications, 2014, 5(1): 4548.

DOI：10.1038/ncomms5548

Obtaining reliable estimates of the absolute palaeointensity of the Earth's magnetic field is notoriously difficult. The heating of samples in most methods induces magnetic alteration-a process that is still poorly understood, but prevents obtaining correct field values. Here we show induced changes in magnetic domain state directly by imaging the domain configurations of titanomagnetite particles in samples that systematically fail to produce truthful estimates. Magnetic force microscope images were taken before and after a heating step typically used in absolute palaeointensity experiments. For a critical temperature (250 degrees C), we observe major changes: distinct, blocky domains before heating change into curvier, wavy domains thereafter. These structures appeared unstable over time: after 1-year of storage in a magnetic-field-free environment, the domain states evolved into a viscous remanent magnetization state. Our observations qualitatively explain reported underestimates from otherwise (technically) successful experiments and therefore have major implications for all palaeointensity methods involving heating.

• 出版日期2014-8