Speaker
Description
The magnetic properties of rare-earth ions are mainly studied in the periodic and symmetrical crystal structures. The influence of the crystal-electric field (CEF), which surrounds the magnetic ions in such cases, is mainly identical for every magnetic ion.
We performed the experimental study of the magnetic properties of the Dy$_x$Y$_{1-x}$(PO$_3$)$_3$ glassy system with several concentrations of Dy$^{3+}$ ions, $x = 0$, $0.01$, $0.1$, $1$, $10$, and $100$ $\%$. The excess over the Debye contribution, called the boson peak, characterizes the specific heat $C_p$ of the non-magnetic sample ($x = 0$) at $T_{BP}\approx 12$ K [1], which is typical for the amorphous material. Additional magnetic contributions are observed in the magnetic samples ($x\neq 0$), revealed as an onset of Shottky maximum in the $x = 100$ sample [1]. The magnitude of the maximum decreases with the decreasing content of the magnetic ions. The external magnetic field application shifts the Shottky maximum to higher temperatures, which is connected with reducing the magnitude.
The magnetization measurements showed that saturated magnetization was lower than the expected saturation value $\mu_{eff} = 10.65\mu_B$ at $T= 1.8$ K due to the strong anisotropy of the Dy$^{3+}$ ions. Magnetic susceptibility measurements between $T=1.8$ K and $300$ K in the temperature range revealed no difference between zero field cooling and field cooling regimes, indicating the absence of magnetic phase transitions. The fitting procedure using Curie-Weiss law showed weak antiferromagnetic interactions, which decrease with lowering Dy$^{3+}$ concentrations. The effective magnetic moment at $T=300$ K indicates values close to $\mu_{eff} = 10.65\mu_B$.
AC susceptibility experimental study revealed the presence of slow magnetic relaxation in zero magnetic field characterized by the presence of one relaxation process. The relaxation process slows down with decreasing magnetic concentration. Sample with $x=100$ $\%$ relax above $f=10$ kHz, $x=10$ $\%$ at $f=3000$ Hz, $x=1$ % at $f=730$ Hz, $x=0.1$ $\%$ at $f=20$ Hz and $x=0.01$ $\%$ below $f=0.1$ Hz. This may be caused by the weakening of the magnetic interactions between Dy$^{3+}$ ions.
Acknowledgements
The work was supported by the project APVV-22-0172.
References
[1] P. Baloh et al., “Thermodynamic properties of the phosphate glass Dy(PO3)3 – Potential influence of boson peak on spin relaxation,” Journal of Magnetism and Magnetic Materials, vol. 588. Elsevier BV, p. 171415, Dec. 2023. https://doi.org/10.1016/j.jmmm.2023.171415
