Beschreibung:
<jats:p>The aim of this work is to discuss some magnetic data of as-cast Re4Fe1 alloys (Re=Nd,Pr,Sm) as well as to study the influence of hydrogen absorption on their structural and magnetic properties. The pallets of 1 g were prepared by arc melting Nd,Pr,Sm, and Fe (purity 99.9%) under Ar. Structural analyses were performed using a standard x-ray diffractometer. The high-temperature magnetization was studied by a vibrating sample magnetometer in the temperature range of 300–1200 K and permanent magnetic fields up to 7 kOe. The high-field magnetization studies in fields up to 140 kOe in the temperature range from 4.2 to 300 K were performed by an extraction magnetometer. The hydrogen absorption processes were studied by a volumetric apparatus within the hydrogen pressure range of 10–4×103 kPa in the temperature range of 270–573 K. The x-ray and the magnetic measurements were performed on the samples of alloys and hydrides with H concentration of 2.8 at. %/mol. x-ray diffractograms for parent Re4Fe1 alloys showed the presence of two allotrope-hexagonal P6mmc and cubic structures. The existence of a small amount of amorphous phase cannot also be excluded. X-ray patterns of Re4Fe1H2.7 (Re=Pr, Nd) showed well-defined first and second diffuse haloes and the presence of some smeared diffraction peaks corresponding to the bcc structure, typical for Re-H3 systems.</jats:p>
<jats:p>Magnetic ordering temperatures were determined to be 515 and 502 K for Nd4Fe1 and Pr4Fe1, respectively. Formation of the hydride phases results in decreasing of the coercivity Hc. At room temperatures Hc was found to be 4.5 kOe and 60 Oe for as-cast Nd4Fe1 and its hydride, respectively. It should be noted that absorption of hydrogen increases the net magnetic moment. A strong thermomagnetic effect was observed in the magnetic fields up to 60 kOe for the alloys. In the case of zero-field cooling of the Nd4Fe1 sample the value of magnetization at 25 kOe is 3.4 μB/mol (4.2 K) and 5.0 μB/mol when the sample is cooling in the same field. The last observation as well as the presence of a minimum in the temperature dependence of magnetization around T=60 K at a field 25 kOe for Nd4Fe1 and Pr4Fe1 showed the strong influence of the anisotropy on the magnetic moments of the iron sublattice.</jats:p>