Resonance magnetoplasticity in ultralow magnetic fields

Resonance relaxation displacements of dislocations in NaCl crystals placed in crossed static and alternating ultralow magnetic fields in the electron paramagnetic resonance scheme are discussed. The Earth's magnetic field $B_{\text{Earth}}\approx50\mu\mathrm{T}$ and other fields in the range of $26{-}261 \mu\mathrm{T}$ are used as the static field. New strongly anisotropic properties of the effect have been revealed. Frequency spectra including numerous peaks of paths at low pump frequencies beginning with $10$ kHz, as well as the quartet of equidistant peaks at high frequencies ($\sim1.4$ MHz at $B=B_{\text{Earth}}$), have been measured. The effect is also observed in the pulsed pump field with a resonance duration of $\sim0.5 \mu s$. Resonance changes have been detected in the microhardness of ZnO, triglycine sulfate, and potassium hydrogen phthalate crystals after their exposure in the Earth's magnetic field in the same electron paramagnetic resonance scheme.