![]() Then the sample was warmed back to RT in 10 hours and diffractograms were collected every 15 minutes. At this temperature, a 4.5 hours isotherm acquisition was performed. Then the PE cell was cooled using liquid nitrogen and helium from RT to 5 K. A pressure of 0.12 GPa was applied to the PE cell, which for the sample corresponded to 8 GPa, after calibration with a Pb flake placed with the sample. Then, it was introduced inside a VX5/180 Paris-Edinburgh (PE) pressure cell 36, 37 equipped with SINE-type sintered diamond anvils 38. at 20 GPa 25), which is the typical in all the neutron diffraction experiments. For these acquisitions, the powder was placed in a null-scattering TiZr gasket using a deuterated 4:1 ethanol-methanol mix as pressure transmitter medium, (the same that the one employed before by Perreault et al. The data collection at 8 GPa were performed with \(\lambda =2.52\) Å which correspond to the maximum flux configuration of the D1B instrument. Two data acquisitions were taken at AP and room temperature (RT) for a Ho powder sample inside a 6 mm diameter vanadium can, with neutron wavelengths of \(\lambda =1.28\) Å and 2.52 Å which allowed to explore d-spacings, respectively, of 0.7–15.0 Å and 1.4–50 Å. A Radial Oscillating Collimator (ROC) was installed in order to eliminate the spurious signals produced by the sample environment. This instrument has a MWGC 1D-detector spanning an angular range of 128 \(^\circ\) with a definition of 0.1 \(^\circ\). Neutron powder diffraction experiments were carried out on the high-flux 2-axis neutron diffractometer D1B of the Institut Laue-Langevin (ILL) in Grenoble, France. Especial care was taken to manipulate the sample minimizing the exposure time to air. Polycrystalline sample of metallic natural Ho with high purity (99.999 \(\%\)) was purchased from Sigma-Aldrich. The magnetic superspace group (MSSG) formalism 33, 34, 35 has been employed to classify the symmetry of the magnetic structure. ![]() The spatially damped oscillation of the spin polarization of the conduction electrons is responsible of the competition between the ferromagnetic (FM) and antiferromagnetic (AFM) interactions, which often results in an incommensurate helimagnetic structure (HM). On the other hand, the ferromagnetism in the 4 f-electron lanthanide metals, such as Gd, Tb, Dy, Ho, Er, and Tm, is explained by the Ruderman–Kasuya–Kittle–Yosida (RKKY) interaction between localized moments of the 4 f-electrons mediated by the conduction electrons 3, 4, 5. In particular, in the 3 d transition metals based on Fe, Co, and Ni, the mechanism responsible for their ferromagnetism can be understood within the Stoner model 2. Magnetism of itinerant electrons 1 have played an important role in condensed matter physics to explain the properties of ferromagnetic metals. ![]()
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