Magnetic relaxation in Zn(PO3)2·Er(PO3)3 glass

• The boson peak in Zn(PO3)2·Er(PO3)3 glass appears at temperatures, at which localized modes are thermally excited.
• The formation of the boson peak is accompanied by anomalous slowing of the magnetic relaxation in Zn(PO3)2·Er(PO3)3.

The results of experimental studies of alternating (ac) magnetic susceptibility and specific heat of Zn(PO3)2·Er(PO3)3 glass are reported. Despite a high concentration of magnetic Er(III) ions the analysis of ac susceptibility ruled out the formation of a spin glass state in the used range of temperatures. Two relaxation processes were identified. The first one is thermally activated with a crossover in its temperature dependence observed at nominally 7 K. The relaxation at lower temperatures seems to be governed by a direct process with pronounced effect of phonon bottleneck. Striking deceleration of spin dynamics with increasing temperature found above 7 K is tentatively attributed to overcoming Ioffe – Regel crossover and strong scattering of acoustic phonons on local modes. Simplified prediction derived from a soft-mode-dynamics model confirms the presence of the boson peak observed in specific heat data and reasonably predicts the temperature of the crossover. The second process is consistent with a cross – tunneling relaxation. The obtained results suggest that magnetic doping of glasses and studying magnetic relaxation may represent an alternative tool for the investigation of lattice modes in glasses.

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