Magnetic Structures of R₃Pd₄Ge₄ (R=Tb and Er)

E. Wawrzyńska^a, J. Hernández-Velasco^b, B. Penc^a, M. Rams^a, A. Szytuła^a#

^aM. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland

^bBENSC, Hahn-Meitner Institut, Glienicker Straße 100, D-14109 Berlin-Wannsee, Germany

Abstract

Polycrystalline samples of R₃Pd₄Ge₄ (R=Tb and Er) intermetallics were studied with magnetometric and neutron diffraction methods. Both compounds crystallize in the orthorhombic Gd₃Cu₄Ge₄-type structure in which the rare earth atoms occupy two inequivalent crystallographic positions. Both compounds order antiferromagnetically below their Néel temperatures of about 13 K in case of Tb₃Pd₄Ge₄ and about 4 K in case of Er₃Pd₄Ge₄. These transition temperatures are confirmed by magnetic measurements. The magnetic structures were studied with the support of group theoretical considerations. For R=Tb both sublattices order simultaneously and the magnetic ordering is described by two propagation vectors. One of them is k₁=(0,0,0) and describes the ordering in the 4e sublattice whereas the second one: k₂=(0,0.212(1),0.788(1)) describes the ordering in both 2d and 4e sublattices. In case of the Er compound the magnetic structure is also described by two propagation vectors: k₁=(0,0,0) which describes the ordering in the 4e sublattice whereas the second one: k₂=(0,0.139(2),0) describes the ordering in the 2d sublattice.