Magnetic properties of the Ag–In–rare-earth 1/1 approximants

Abstract

Abstract. We have performed magnetic susceptibility and neutron scattering measurements on polycrystalline Ag-In-RE (RE: rare-earth) 1/1 approximants. In the magnetic susceptibility measurements, for most of the RE elements, inverse susceptibility shows linear behaviour in a wide temperature range, confirming well localized isotropic moments for the RE 3+ ions. Exceptionally for the light RE elements, such as Ce and Pr, non-linear behaviour was observed, possibly due to significant crystalline field splitting or valence fluctuation. For RE = Tb, the susceptibility measurement clearly shows a bifurcation of the field-cooled and zero-field-cooled susceptibility at T f = 3.7 K, suggesting a spin-glass-like freezing. On the other hand, neutron scattering measurements detect significant development of short-range antiferromagnetic spin correlations in elastic channel, which accompanied by a broad peak athω = 4 meV in inelastic scattering spectrum. These features have striking similarity to those in the Zn-Mg-Tb quasicrystals, suggesting that the short-range spin freezing behaviour is due to local high symmetry clusters commonly seen in both the systems.

Magnetic Orders in Compounds Made of Icosahedral Rare-Earth Clusters

“…For both systems, specific heat also displays anomalies and/or peaks at the transition temperatures (not shown) indicating that the successive transitions are due to long-range magnetic orders. These results in Cd 6 RE are different from the spin glass-like behaviors observed in, for instance, Ag-In-RE approximants [14] . The present work clearly shows that long-range magnetic orders are allowed for 4f magnetic moments sitting on the vertices of an icosahedron.…”

Magnetism in icosahedral quasicrystals: current status and open questions

“…The magnetic properties of the 1/1 cubic approximant phases were investigated for the full series of R ions [99]. For R = Nd, Eu, Gd, Tb, Dy, Ho, Er and Tm, the dc magnetic susceptibilities at high temperature ( 100 K) exhibit Curie–Weiss behavior and the effective moments are consistent with the free ion values for (or for Eu).…”

“…For the R -Ag-In approximants, the low temperature magnetic susceptibility measurements revealed a splitting between the FC and ZFC susceptibilities for R = Eu, Gd, Tb and Dy with largest for Tb (3.7 K). Taking the ratio of again as a measure of magnetic frustration in the system, they found values ranging from 17 for R = Gd to 7 for R = Tm classifying the approximants as highly frustrated magnetic systems [99]. …”

Antiferromagnetic order in the quasicrystal approximant Cd6Tb studied by x-ray resonant magnetic scattering

“…21 For rare-earth based approximants, where the exchange is dominated by the longrange RKKY interaction, extensive magnetic property investigations found spin-glass-like freezing of the moments in AgIn-R 1/1 cubic approximants for R = Eu, Gd, Tb and Dy. 22 Furthermore, both the Ag-In-Gd icosahedral phase and its 1/1 cubic approximant show similar behavior as both evolve to spin-glasses at low temperature. 23 Surprisingly, the 1/1 approximant to the Cd-Mg-R icosahedral phases, Cd 6 R, appears to be an exception to the rule.…”