Magnetism of β′-Gd₂(MoO₄)₃ and photoluminescence of β′-Eu₂(MoO₄)₃ crystallized in rare-earth molybdenum borate glasses

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Ferroelastic β′-Gd₂(MoO₄)₃ and β′-Eu₂(MoO₄)₃ crystals were synthesized through the crystallization of 21.25Gd₂O₃–63.75MoO₃–15B₂O₃ glass and 22.5Eu₂O₃–47.5MoO₃–30B₂O₃ glass, respectivelty, and their magnetism and photoluminescence properties were examined. It was demonstrated from the temperature dependence of the magnetic susceptibility and specific heat down to T = 1.8 K that the magnetic state of Gd³⁺ ions in the crystallized samples, i.e., in the β′-Gd₂(MoO₄)₃ crystals and the residual glasses, is paramagnetic and any magnetic interaction is not formed among Gd³⁺ ions down to T = 1.8 K, i.e., the effective magnetic moment of µ_eff = 7.94 µ_B and Weiss constant of θ = –0.3 K. Photoluminescence (PL) of Eu³⁺ ions was clearly observed in the crystallized samples, although the melt-quenched glass did not show any photoluminescence. The present study proposes that the concentration quenching among Eu³⁺ ions in β′-Eu₂(MoO₄)₃ crystals is small and β′-RE₂(MoO₄)₃ crystals would be good hosts for PL emissions of RE³⁺.