Transformation of the mechanical properties of materials by the geomagnetic resonance

TL;DR

This paper investigates how ultralow magnetic fields, including Earth's magnetic field, influence the mechanical properties of crystals through geomagnetic resonance, revealing anisotropic effects and resonance-dependent changes.

Contribution

It presents new experimental evidence of geomagnetic resonance effects on crystal dislocations and hardness, highlighting anisotropic properties and resonance sensitivity.

Findings

Resonance relaxation displacements observed in NaCl crystals.

Microhardness changes detected in ZnO, triglycine sulfate, and potassium acid phthalate.

Resonance frequency highly sensitive to sample orientation relative to Earth's field.

Abstract

The strong geomagnetic influences on mechanical properties of crystals due to their exposure to ultralow crossed magnetic fields, the Earth's field (approx. 50 microTesla) and the AC field (approx. 3 microTesla) in the electron paramagnetic resonance scheme, are discussed. Resonance relaxation displacements of dislocations in NaCl crystals are found both for a harmonic pump field and for a pulse AC field of resonance duration approx. 0.5 microsec. Resonant changes have been also detected in the microhardness of ZnO, triglycine sulfate, and potassium acid phthalate crystals after their exposure in the same EPR scheme. The both effects manifest new strongly anisotropic properties. In particular, the frequency of the resonance is very sensitive to the mutual orientation of the sample and the Earth's field. Physical mechanisms and practical significance of the phenomenon are discussed.