Complex magnetic ordering in RE5Pd2In4 (RE = Tb-Tm) compounds investigated by neutron diffraction and magnetometric measurements

The RE5Pd2In4 (RE = Tb-Tm) compounds crystallize with the orthorhombic Lu5Ni2In4-type crystal structure (Pbam space group). In this work we report results of structural and magnetic studies by means of X-ray and neutron diffraction as well as dc and ac magnetometric data. Magnetic susceptibility and neutron diffraction data revealed rare-earth moments order at low temperatures with complex magnetic structures showing a cascade of temperature-induced transitions. The magnetic ordering temperatures are found to be 97, 88, 28.5, 16.5 and 4.3 K for RE = Tb, Dy, Ho, Er and Tm, respectively. Magnetic structures related to the propagation vector (k(1)) over right arrow = [0, 0, 0] are found just below the magnetic ordering temperatures in majority of the investigated compounds (RE = Tb-Er). Below the Curie temperature T-C they have purely ferromagnetic character in Tb5Pd2In4 and Dy5Pd2In4. A ferrimagnetic order finally sets at lower temperatures in Dy5Pd2In4, while in Ho5Pd2In4 two magnetic phases related to (k(1)) over right arrow are observed: the antiferromagnetic one (phase I) and the ferrimagnetic one (phase II, coexisting with phase I at lower temperatures). Er5Pd2In4 is a canted antiferromagnet with additional ferromagnetic component developing at lower temperatures. A purely antiferromagnetic component of magnetic structure with enlarged magnetic unit cell appears with decreasing temperature in Tb5Pd2In4 ((k(2)) over right arrow =[0, 1/2, 0] and (k(3)) over right arrow =[0, 1/2, 1/2]) while in Ho5Pd2In4 such component ((k(4)) over right arrow = [1/4, 0, 0]) is present within whole temperature range below the magnetic ordering temperature. Magnetic structure of Tm5Pd2In4, exceptionally, has no (k(1)) over right arrow component, but is an antiferromagnetic incommensurate one related to two propagation vectors: (k(5)) over right arrow = [0.073(3), 0.451(1), 1/2] and (k(6)) over right arrow = [0, 0.335(2), 1/2]. In majority of the compounds (RE = Tb-Er) the first 1 rare-earth 4g site (noted as 4g1) orders at lower temperature than two remaining sites (2a and 4g2). The direction of the magnetic moments depends on rare-earth element involved and indicates an influence of single-ion anisotropy in the crystalline electric field (CEF). (C) 2021 The Author(s). Published by Elsevier B.V. CC_BY_4.0