The influence of hydrostatic pressure (up to 5 kbar) on the magnetic structure of Ce2Fe17 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, mFe=2.0 μB, 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 τ1=0.026 Å−1 at 100 K to τ1=0.034 Å−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 τ2≈0.078 Å−1 at 40 K under pressures above 3 kbar. The correlation with recent results of magnetization studies under pressure is analyzed and discussed.

The measurements of the magnetization in high steady and pulsed fields together with neutron diffraction measurements on a powder sample and on a single crystal have been performed to study the magnetic state of the Tb 3 Co compound. It has been shown that the modulated antiferromagnetic structure which exists in Tb 3 Co below T N = 82 K transforms to the incommensurate magnetic structure with a strong ferromagnetic component along the c-axis with further cooling below the critical temperature T t ≈ 72 K. The phase transition from the high-temperature to the low-temperature magnetic state at T t is of first order. The incommensurability of the low-temperature magnetic structure of Tb 3 Co is attributed to the non-Kramers character of the Tb 3+ ion in combination with competition between the indirect exchange interaction and the low-symmetry crystal electric field.

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The crystal and magnetic structures of the TbNi 2 Mn compound have been refined by the Rietveld analysis of neutron powder-diffraction data. The compound has a cubic C15b-type structure, in which Mn atoms partially occupy both the 4a and 16e sites. Bulk magnetization measurements revealed magnetic ordering below the Curie temperature T C = 142 K. The values of magnetic moment are different for the Tb ion at the 4a and 4c positions. In the 4c site, the Tb moment is determined to be 5.4 B / Tb ion. The low value of the Tb-ion moment is indicative of the formation of a random magnetic anisotropy.