Interplay between crystal structure and magnetic susceptibility of tetragonal ROBr

Abstract

The average magnetic susceptibilities for trivalent rare earth (R 3+ ) ions in polycrystalline tetragonal rare earth oxybromides (ROBr, R ¼ Ce-Nd, Sm, Eu, and Tb-Yb) were measured between 2 and 298 K. The susceptibilities of all ROBr follow the paramagnetic Curie-Weiss behaviour down to low temperatures except for SmOBr and EuOBr where the effect of crystal field was observed already above 200 K. The observed effective magnetic moments m eff (RT) were generally higher than the free ion values. For the heavier R 3+ ions (Ho 3+ and Er 3+ ) m eff was found to be less than the free ion value due to crystal field mixing in the opposite way. The Weiss constant y was found to be negative for all ROBr, suggesting antiferromagnetic (AFM) ordering at lower temperatures but only SmOBr (SmOCl) and DyOBr (DyOCl) show such ordering at 5(8) and 8(11) K, respectively. The increasing interlayer distance between adjacent (RO) nþ n layers from ROCl to ROBr and within the ROBr series lowers the Ne ´el temperature. AFM ordering thus depends on the 3D interactions while 2D interactions have negligible effect. The temperature dependence of the experimental paramagnetic susceptibility for each ROBr was simulated with the aid of the van Vleck formalism based on the wave functions and energy level values obtained from spectroscopic data. Lattice expansion and consequent modifications in crystal field caused discrepancies at higher temperatures.

Crystal and magnetic structure of CeVO3

“…This is much smaller than gJ = 2.14 μ B , the theoretical moment of the Ce 3+ ion (electron configuration 4f 1 , J = 5/2). While the magnetic moments of many insulating Ce 3+ compounds (such as CeOBr, [25]) are in good agreement with the free-ion value, significant deviations have been observed in some oxides (such as Ce 3+ impurities in (Sr,Ca,Ba)O [26]). Possible origins include partial quenching of the orbital moment by the crystal field, covalency with ligand ions, and orbit-lattice interactions.…”

Salt‐Effect‐Based Synthesis and Anomalous Magnetic Properties of Rare‐Earth Oxide Nanosheets with Sub‐1 nm Thickness

“…Thus, the effective magnetic moments of Gd 3+ are 8.26, 8.08, and 9.45 μ B , respectively. The effective magnetic moments of Gd 3+ in bulk phase Gd 2 O 3 and colloidal Gd 2 O 3 NS1 are both close to that of free Gd 3+ ion in the ground state, that is, 7.94 μ B 13. However, the effective magnetic moment of Gd 3+ in colloidal Gd 2 O 3 NS2 is significantly larger than 7.94 μ B .…”

Structural, magnetic and spectroscopic investigations of europium oxychloride, EuOCl

“…4) is complex: characteristic to a Curie-Weiss paramagnet at high temperatures and then constant for the lower temperature range between 75 and 25 K. Finally, a sharp decrease is observed below the lower temperature of the constant magnetic susceptibility range. The constant magnetic susceptibility can be qualitatively explained by the exceptional 7 F J (J = 0-6) ground term energy level scheme of the Eu 3+ ion [10]. The 7 F 0 ground level is non-magnetic and gives no contribution to the susceptibility of EuOCl at low temperatures and the magnetic susceptibility depends exclusively on the population of the excited CF levels.…”

“…The motivation for this study was initially given by the observation that the trivalent rare earth oxyhalides of praseodymium (PrOX) and terbium (TbOX) could be prepared successfully by using the partly tetravalent oxides, Pr 6 O 11 and Tb 4 O 7 [9,10]. Even though there is no direct evidence of the luminescence of the Eu 2+ ion in the previous spectroscopic studies of the Eu 3+ ion in different R oxyhalide matrices [11][12][13] the possibility of such a valence change should not be neglected.…”