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Rare-Earth Hafnium Molybdates: A Structural, Optical, and Magnetic Study
Md Abdullah Al Muhit1, Habiba Binte Kashem1, Hope Eden Catalano1
1Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina29208, United States.
Abstract:
The molten flux method was used to grow crystals belonging to two different classes of rare-earth hafnium molybdates, RE2Hf3(MoO4)9 and RE2Hf2(MoO4)7, whose luminescence and magnetic properties were investigated. The first structure type, RE2Hf3(MoO4)9, spans from La to Eu (except Pm) and crystallizes in the trigonal R-3c space group. In this structure, MoO4, REO9, and HfO6 are connected via their corners. The MoO4 units form open channels along the c-axis, which are occupied by columns of REO9 and HfO6 polyhedra. The second structure type, RE2Hf2(MoO4)7, includes RE = Sm, Eu, Gd, Tb, and Dy and crystallizes in the monoclinic C2/c space group. The MoO4 tetrahedra connect through their corners to HfO6 octahedra and DyO8 square antiprisms, forming a three-dimensional open framework. Magnetic and photoluminescence properties were measured on polycrystalline samples obtained from solid-state reactions. Eu2Hf3(MoO4)9 and Tb2Hf2(MoO4)7 exhibit photoluminescence under UV irradiation. Eu(III) was doped successfully into La2Hf3(MoO4)9 and characterized by single-crystal X-ray diffraction and single-crystal photoluminescence emission spectroscopy. Magnetic susceptibility vs temperature measurements were performed to investigate the magnetic behavior of Ce2Hf3(MoO4)9, Gd2Hf2(MoO4)7, and Dy2Hf2(MoO4)7.
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