Magnetic isotopic effect in the plasticity of diamagnetic crystals

A magnetic isotopic effect in the plasticity of diamagnetic crystals is predicted. This effect consists in that the replacement of nonmagnetic isotopic nuclei by magnetic nuclei in ionic crystals (e.g., the introduction of ²⁵Mg²⁺ or ⁴³Ca²⁺ in place of ²⁴Mg²⁺ or ⁴⁰Ca²⁺ in NaCl) increases the plasticity of the crystals even in the absence of an external magnetic field. On the contrary, such a replacement in covalent crystals (e.g., the introduction of ²⁹Si into silicon or ¹³C into diamond) is expected to reduce the plasticity and to produce dislocation strengthening.