Abstract
The non-stoichiometric intermetallic compounds RENi2Mnx (RE = rare earth) with the cubic MgCu2-type structure display a large variety of magnetic properties which is due to a complex interplay between the degrees of freedom of the 3d and 4f electrons and their interactions. We performed a comprehensive study of the electrical resistivity, magnetic properties and the electronic structure of ErNi2Mnx (x =0, 0.25, 0.5, 0.75, 1, 1.25) compounds by employing a suitable set of complementary experimental approaches. We find an increase in electrical resistance compared to ErNi2 upon Mn doping, the residual resistivity ratio decreases with increasing manganese content. The Curie temperature exhibits a sharp increase to around 50 K for Mn concentrations x ≥ 0.5, whereas the saturation magnetization decreases with growing Mn content x ≥ 0.5. Valence band X-ray photoelectron spectroscopy reveals an increasing intensity of Mn 3d states near Fermi energy in dependence of Mn concentration and Curie temperature. Resonant photoelectron spectroscopy of ErNi2Mn0.75 reveals that the photoemission decay channels dominate the valence band spectra across the Er N5 and Mn L3 X-ray absorption maxima, whereas the L3VV Auger dictates the resonant valence band spectra close to and at the Ni L3 X-ray absorption edge.
Highlights
Rare earth (RE) and transition metal based compounds are of great scientific interest since the 1960s.1,2 The combination of 4f lanthanides, which exhibit large magnetic moments including significant orbital contributions and anisotropy, with the more itinerant magnetism of 3d transition metals leads to a number of fascinating magnetic properties which are due to an intricate competition of the 4f – 4f, 4f – 3d, and 3d – 3d interactions in such compounds
We investigated the electronic structure by valence band X-ray photoelectron spectroscopy (XPS), and for the sample with x = 0.75 we employed complementary X-ray absorption spectroscopy (XAS) in combination with resonant X-ray photoelectron spectroscopy (ResPES) across the Mn L2,3, Ni L2,3 and Er N4,5 edges
For the studied compounds ErNi2Mnx with 0 ≤ x ≤ 1, X-ray diffraction patterns at room temperature can be well described on the assumption of the only cubic Laves phase C15 which belongs to Fd3m space group
Summary
With the MgCu2 -type face-centered cubic structure (Laves phase C15) are widely studied since they combine a relatively simple crystal structure and unique magnetic properties such as giant magnetostriction[10] and large magnetocaloric effect.[11,12]. It was accepted for a long time that the Laves phase compounds have no homogeneity range. The RENi2Mnx systems give the opportunity to gradually modify both magnetic moments and exchange interactions in the Laves phase compounds by changing in a wide range the manganese content.
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