New Magnetic Zintl Phases in Eu-In-P System
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New Magnetic Zintl Phases in Eu-In-P System Jiong Jiang, Amy C. Payne, and Susan M. Kauzlarich Departments of Chemistry, One Shields Avenue, University of California, Davis, CA 95616 ABSTRACT Single crystals of two new compounds, Eu3InP3 and Eu3In2P4, were prepared by In flux synthesis. Eu3InP3 crystallizes in the Pnma orthorhombic space group with a = 12.6517(15) Å, b = 4.2683(5) Å, c = 13.5643(14) Å, and Z = 4 while Eu3In2P4 belongs to Pnnm space group, a = 6.6999(6) Å, b = 16.1019(13) Å, c = 4.2725(4) Å, and Z = 2. These two compounds are isotypic to the main group compounds Sr3InP3 and Sr3In2P4 respectively. Both structures consist of distorted In-P tetrahedra and isolated Eu2+ ions. In Eu3InP3 these tetrahedra share corners to form one-dimensional chains. The Eu2+ ions occupy three different sites, and form a complicated network containing some triangles. In Eu3In2P4 these tetrahedra form edge-shared dimers, and these dimers form chains. Eu3InP3 shows unusual magnetic properties: there are three magnetic ordering transitions at 14 K, 10.4 K, and around 5 K and the magnetization curve shows steps in the low temperature region. Eu3In2P4 magnetically orders at 14.5 K. Its magnetization curve saturates at around 1T. Eu3InP3 and Eu3In2P4 are both semiconductors. INTRODUCTION Zintl phases are compounds with a precise valence count. These compounds consist of elements from group 1, 2 with those from group 13, 14, 15. In recent decades, scientists have extended the Zintl boundary to include transitional metals and rare earth metals because of their special electron configuration.1-4 By doing so, many compounds with new structure types and novel physical properties have been discovered.5, 6 Zintl phases containing europium have been attracting much attention. There are several ternary europium compounds that show unusual magnetic properties. EuNi5P3 has a magnetization curve with several steps resulted from magnetic spin-flop and thermally activated domain wall motion.7 Similar steps also occur in EuAs3. Studies on this compound suggest that temperature and field dependence of the lattice size are important.8 Eu containing Zintl phases are typically antiferromagetic with low magnetic ordering temperature,9, 10 however, many of them show a positive Weiss constant, which suggests a ferromagnetic correlation in the paramagnetic region.11, 12 Here we introduce two europium containing Zintl phases, Eu3InP3 and Eu3In2P4. EXPERIMENT DETAILS Eu3InP3 and Eu3In2P4 were synthesized by heating a mixture of the elements. The starting materials were Eu (99.999%, Ames Lab) 1/8” ribbon, cut into small pieces, red P (J. Matthey, Puratronic), crushed into small pieces, and In shot (Aesar, 99.99%), used as received. In the reactions, indium acts as both reactant and flux.13 The europium and phosphorus were packed into an alumina crucible between layers of granular indium metal. A second crucible containing quartz wool was inverted over the reaction crucible, and the entire reaction vessel was sealed in a fused silica jacket that
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