Magnetovolume effects in substituted Er 1−xGd xMn 6Sn 6 intermetallics

Abstract

The thermal expansion and spontaneous magnetostriction of polycrystalline samples of Er 1−xGd xMn 6Sn 6 (0 ≤ x ≤ 1) intermetallics with hexagonal HfFe 6Ge 6-type structure are investigated in the temperature range of 77–520 K. The Gd substitution has significant effect on the interatomic distances and especially on inter-sublattice R–Mn couplings. The replacement of Er by Gd causes the lattice constants to increase due to the larger atomic radius of Gd compared with Er. It also results in increasing the ordering temperature as well as the spontaneous magnetostriction values following reinforcement the R–Mn coupling. The examined samples exhibit considerable thermal expansion anomalies at the Néel temperature ( T N = 340 and 335 K for the samples with x = 0 and 0.2, respectively) and also at T M = 309–311 K where the Mn moments experience collapse-like reduction. Whereas, trivial anomalies are revealed at the Curie points ( T C = 77 K for the sample with x = 0, 164 and 383 K for x = 0.2, 419 and 434 K for x = 0.6 and 1, respectively). From the results, it is concluded that the magnetovolume effects in these compounds originate mainly from the antiferromagnetic interlayer Mn–Mn exchange interactions, and the intraplane ferromagnetism does not influence the magnetoelasticity.