loading page

Magnetic fatigue: Effect of seismic-related loading on magnetic and structural behavior of magnetite
  • Boris Reznik,
  • Agnes Kontny,
  • Frank R. Schilling
Boris Reznik
Karlsruhe Institute of Technology

Corresponding Author:[email protected]

Author Profile
Agnes Kontny
Author Profile
Frank R. Schilling
Karlsruhe Institute of Technology
Author Profile


Powders of multidomain magnetite were subjected to fatigue, cyclic loading at ambient conditions between 30 and 500°C using a dynamical mechanical analysis system. The uniaxial static force of 6 MPa was modulated with 3 MPa using 1, 10 and 100 Hz frequencies. Microstructural analysis was performed by a combination of X-ray diffraction analysis with optical microscopy. Magnetic properties were studied by low-temperature magnetic susceptibility across the Verwey transition and hysteresis behavior measured at room temperature. Irreversible microstructures and magnetic signatures indicate the onset of magnetic fatigue in magnetite. The increasing mechanical losses, are proportional to the growing loading frequency and correlate with decreasing coherent crystallite size and lattice parameters in magnetite as well as with its lattice distortion. Hematite at grain boundaries of crashed magnetite is documented by microscopy, however, magnetic analysis indicates that magnetite is still the main magnetic carrier in the fatigue-loaded samples and therefore, the changes in magnetic properties are dominantly related to magnetic fatigue. The decay of magnetic susceptibility above is independent of the occurrence of hematite but is more sensitive to lattice strain and reduction of magnetic domains. The refinement of magnetic domains is also demonstrated by the evolution of hysteresis parameters and FORC diagrams, both indicating multidomain to pseudo-single domain transition. As the applied loading frequencies are similar to those observed during earthquake propagation or volcano eruption, it is therefore discussed how the acquired signatures of magnetic fatigue can be used as proxies of natural seismic-related loadings.