Thermodynamic properties of the phosphate glass Dy(PO3)3 – Potential influence of boson peak on spin relaxation

An experimental study was conducted to investigate the magnetic properties of dysprosium-doped phosphate glasses. Low-temperature (LT) measurements of the specific heat of Dy(PO ₃) ₃ were performed in the range of 0.38–300 K in the magnetic fields up to 9 T. The LT specific heat of amorphous materials is characterized by the presence of a broad maximum named boson peak (BP). The LT specific heat of the Dy-doped sample is dominated by the magnetic contribution, which overlaps the BP. Due to that reason, the specific heat of Y(PO ₃) ₃ nonmagnetic glasses was also measured at the same temperature range, revealing the BP at 12–14 K. The magnetic susceptibility was measured from 1.8 K up to room temperature, yielding the effective magnetic moment of 10.65 {μ}_B, which is close to the theoretical prediction for Dy ³⁺. Magnetization curves were measured up to B = 5 T with temperatures ranging from 2 to 50 K. X-band electron-paramagnetic resonance spectra were measured from 0 to 1 T, revealing a maximum at 100 mT. The line achieves maximal intensity at temperatures around 12–14 K, which coincides with the appearance of BP in specific heat. The coincidence suggests the presence of the magnetoelastic coupling between the ground quasi-doublet and boson peak.