TbMgNi4- xCox-(H,D)2 System. II: Correlation between Structural and Magnetic Properties

Valérie Paul-Boncour; Premysl Beran; Charles Hervoches; Vitalii Shtender

doi:10.1021/acsomega.3c04879

TbMgNi_{4- x}Co_x-(H,D)₂ System. II: Correlation between Structural and Magnetic Properties

ACS Omega. 2023 Aug 9;8(33):30727-30735. doi: 10.1021/acsomega.3c04879. eCollection 2023 Aug 22.

Authors

Valérie Paul-Boncour¹, Premysl Beran^{2

3}, Charles Hervoches², Vitalii Shtender^{1

4

5}

Affiliations

¹ Université Paris-Est Créteil, CNRS, ICMPE, UMR 7182, F-94320 Thiais, France.
² Nuclear Physics Institute, Czech Academy of Sciences, 25068 Rez, Czech Republic.
³ European Spallation Source, ESS ERIC, Box 176, SE-221 00 Lund, Sweden.
⁴ Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, 75121 Uppsala, Sweden.
⁵ Department of Materials Science and Engineering, Uppsala University, 75103 Uppsala, Sweden.

Abstract

The magnetic properties of TbMgNi_4-xCo_x intermetallic compounds and selected hydrides and deuterides of this system have been studied by various techniques, including magnetic measurements, in situ X-ray and neutron powder diffraction. The intermetallic compounds crystallize in a SnMgCu₄-type structure and magnetically order below a Curie temperature (T_C), which increases exponentially with the Co content. This can be due to the ordering of the Co sublattice. On the other hand, the insertion of D or H in TbMgNiCo₃ strongly decreases T_C. The X-ray diffraction measurements versus temperature reveal cell volume minima at T_C for the compounds with x = 1-3 without any hints of the structure change. The analysis of the neutron diffraction patterns for the intermetallics with x = 2 and 3 indicates a slightly canted ferrimagnetic structure below T_C. The Tb moments refined at 16 K are 4.1(2) μ_B/Tb for x = 2, and 6.2(1) μ_B/Tb for x = 3, which are smaller than the free ion value (9.5 μ_B/Tb). This reduction can be due to the influence of temperature but also reveals the crystal field effect. As Ni and Co occupy statistically the same Wyckoff site, an average Ni/Co moment was refined, leading to 1.7(2) μ_B/atom for x = 2 and 1.8(1) μ_B/atom for x = 3 at 16 K. This moment is slightly canted compared to the Tb moment.