Photocontrolled magnetic resonance plasticity of $\gamma$-irradiated KCl:Fe crystals

A photocontrolled resonance decrease in microhardness, which is due to the application of mutually perpendicular static and microwave fields, in $\gamma$-irradiated KCl:Fe crystals has been revealed. It has been found that the magnetic plasticity of unirradiated $\gamma$-KCl:Fe crystals is due to the resonance effect of magnetic fields on two types of impurity centers: first, centers containing Fe$^{2+}$-$v_c$ ion–vacancy pairs and, second, centers containing Fe$^{+}$ ions. The illumination of $\gamma$-KCl:Fe crystals with $F$-light (with a wavelength of $\lambda=500$–$600\,$nm) is accompanied by rearrangement of the spectrum of electron paramagnetic resonance detected by a change in microhardness. The effect of $F$-light on the spectrum of magnetic resonance plasticity is manifested as the suppression of the spectra of Fe$^{2+}$-$v_c$ ions with effective $g$-factors of 7.0 and 3.5 due to their recombination with $F$-electrons and reconstruction to Fe$^{+}$ centers with $g$-factors of $2.2$ and $4.1$.