The influence of hydrostatic pressure (up to 5 kbar) on the magnetic structure of ${\mathrm{Ce}}_2{\mathrm{Fe}}_{17}$ was investigated using neutron diffraction in the temperature range from 2 to 300 K. The existence of a collinear ferromagnetic phase below 95 K with a magnetic moment of Fe, $m_{\mathrm{Fe}}{\text{=2.0\hspace{0.17em}μ}}_B,$ was confirmed at ambient pressure. Magnetic peaks present between 95 and 205 K correspond to an incommensurate antiferromagnetic structure with a wave vector changing its value from ${\tau }_1{\text{=0.026\hspace{0.17em}Å}}^{\text{−1}}$ at 100 K to ${\tau }_1{\text{=0.034\hspace{0.17em}Å}}^{\text{−1}}$ at 205 K. A helical model is used to describe the magnetic structure. Application of high pressures leads to significant changes of the magnetic structure. The ferromagnetic phase, suppressed in the studied temperature range by pressures higher than 3 kbar, gets substituted by a new incommensurate antiferromagnetic phase. This phase can be described as a superposition of the helical structure with a second antiferromagnetic coupling with propagation vector ${\tau }_2{\text{≈0.078\hspace{0.17em}Å}}^{\text{−1}}$ at 40 K under pressures above 3 kbar. The correlation with recent results of magnetization studies under pressure is analyzed and discussed.

In this paper we report comprehensive experimental and theoretical investigation of magnetic and electronic properties of the intermetallic compounds ${\mathrm{Pr}}_2{\mathrm{Fe}}_{17}$ and ${\mathrm{Gd}}_2{\mathrm{Fe}}_{17}$. Electronic structure of these two systems was probed by optical measurements in the spectral range of $0.22–15\mathrm{\mu }\mathrm{m}$. On top of that, charge-carrier parameters (plasma frequency $\Omega$ and relaxation frequency $\gamma$) and optical conductivity $\sigma \left(\omega \right)$ were determined. Self-consistent spin-resolved band-structure calculations within the conventional LSDA+U method were performed. Theoretical interpretation of the experimental $\sigma \left(\omega \right)$ dispersions indicates transitions between $3d$ and $4p$ states of Fe ions to be the biggest ones. Qualitatively the line shape of the theoretical optical conductivity coincides well with our experimental data. Calculated by the LSDA+U method magnetic moments per formula unit are found to be in good agreement with observed experimental values of saturation magnetization.

We present the results of high pressure studies of magnetization, magnetic phase transitions, and related volume anomalies for the intermetallic compound ${\mathrm{Ce}}_{\mathrm{2}}{\mathrm{Fe}}_{\mathrm{17}}$ under hydrostatic pressures up to 10 kbar. The giant negative pressure effect on the ferromagnetic ordering temperature ${\Theta }_T\text{=94\hspace{0.05em}}\mathrm{K}$ was determined: ${\mathrm{d\Theta }}_T\text{/dP=−(38±2)}$ K/kbar. This extraordinary decrease of ${\Theta }_T$ under pressure is not accompanied by the related pronounced decrease of the saturated magnetization under pressure below 2.5 kbar. The effect of pressure on the Néel temperature $T_N\text{=206\hspace{0.05em}}\mathrm{K}$ is less pronounced: ${\mathrm{dT}}_N\text{/dP=−(1.7±0.2)}$ K/kbar. A large positive spontaneous volume magnetostriction that is observed below $T_N$ is suppressed by the application of high pressure and it disappears above 2.5 kbar. A competition of positive and negative exchange interactions between iron atoms is discussed and is thought to be the main reason for the volume anomalies observed. The role of the f electrons of Ce, their possible hybridization with d states of Fe, and their role in magnetic properties of the ${\mathrm{Ce}}_{\mathrm{2}}{\mathrm{Fe}}_{\mathrm{17}}$ compound is not yet clear.