Crystal and magnetic structures of R 2Ni1.78In compounds (R = Tb, Ho, Er and Tm)

Stanisław Baran,Bogusław Penc,Andrzej Szytuła,Yuriy Tyvanchuk,Aleksandra Deptuch,Andreas Hoser

doi:10.1107/s2052520621008179

Abstract

The crystal and magnetic structures in R 2Ni1.78In (R = Ho, Er and Tm) have been studied by neutron diffraction. The compounds crystallize in a tetragonal crystal structure of the Mo2FeB2 type (space group P4/mbm). At low temperatures, the magnetic moments, localized solely on the rare earth atoms, form antiferromagnetic structures described by the propagation vector k = [kx , kx , ½], with kx equal to ¼ for R = Er and Tm or 0.3074 (4) for R = Ho. The magnetic moments are parallel to the c axis for R = Ho or lie within the (001) plane for R = Er and Tm. The obtained magnetic structures are discussed on the basis of symmetry analysis. The rare earth magnetic moments, determined from neutron diffraction data collected at 1.6 K, are 6.5 (1) μB (Er) and 6.09 (4) μB (Tm), while in the incommensurate modulated magnetic structure in Ho2Ni1.78In the amplitude of modulation of the Ho magnetic moment is 7.93 (8) μB. All these values are smaller than those expected for the respective free R 3+ ions. A symmetry analysis of the magnetic structure in Tb2Ni1.78In is also included, as such information is missing from the original paper [Szytuła, Baran, Hoser, Kalychak, Penc & Tyvanchuk (2013). Acta Phys. Pol. A, 124, 994–997]. In addition, the results of magnetometric measurements are reported for Tm2Ni1.78In. The compound shows antiferromagnetic ordering below the Néel temperature of 4.5 K. Its magnetic properties are found to originate from magnetic moments localized solely on the thulium atoms (the nickel atoms remain non-magnetic in Tm2Ni1.78In). The reduction of rare earth magnetic moments in the ordered state in R 2Ni1.78In (R = Tb, Ho, Er and Tm) and the change in direction of the moments indicate the influence of the crystalline electric field (CEF) on the stability of the magnetic order in the investigated compounds.

Highlights

Intermetallic compounds of the R–Ni–In systems are the subject of intensive studies with respect to their crystal structures, chemical bonds and magnetic properties (Kalychak et al, 2004)
The results presented in this work confirm that the ternary
The magnetic and neutron diffraction data indicate that the rare earth magnetic moments in these compounds order antiferromagnetically at low temperatures, with the magnetic structures described by the propagation vector k = [kx, kx, 12], where kx equals

Summary

Introduction

Intermetallic compounds of the R–Ni–In systems are the subject of intensive studies with respect to their crystal structures, chemical bonds and magnetic properties (Kalychak et al, 2004). Within these systems, the compounds with a stoichiometry close to 2:2:1 have been observed to crystallize in two different crystal structures:. (i) A tetragonal one of the Mo2FeB2 type (space group P4/mbm) found for both the R2Ni2In (R = La–Nd) stoichiometric composition and the R2Ni2ÀxIn (x = 0.22, R = Y, Sm, Gd–Tm, Lu) nonstoichiometric composition (Kalychak et al, 1990).

Results

Discussion

Conclusion