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Title: Structure, magnetism, specific heat, and dielectric properties of Eu{sub 2}Ta{sub 2}O{sub 7}

Polycrystalline Eu{sub 2}Ta{sub 2}O{sub 7} containing layered perovskite slabs was prepared and analyzed. Eu{sub 2}Ta{sub 2}O{sub 7} crystallizes in the orthorhombic centrosymmetric Cmcm space group (with unit cell: a = 3.95156(9), b = 27.0775(6), and c = 5.68279(13) Å) isomorphous with high-temperature Sr{sub 2}Ta{sub 2}O{sub 7}. Dielectric measurements reveal that, in contrast to Sr{sub 2}Ta{sub 2}O{sub 7} which is ferroelectric below 166 K, Eu{sub 2}Ta{sub 2}O{sub 7} remains paraelectric down to at least 0.45 K and shows no magneto-dielectric coupling. Magnetic data in the 2–400 K range indicate an antiferromagnetic phase transition with a sharp susceptibility peak at 2.71(5) K. Further analysis using specific heat measurements reveals that the second magnetic phase transition occurs at 1.10(5) K and dominates the spin entropy of the Eu{sup 2+} 4f{sup 7} ions. The possible origin of the two successive magnetic phase transitions in Eu{sub 2}Ta{sub 2}O{sub 7} requires further studies.
Authors:
; ;  [1]
  1. National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan)
Publication Date:
OSTI Identifier:
22392028
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANTIFERROMAGNETISM; DIELECTRIC PROPERTIES; ENTROPY; EUROPIUM COMPOUNDS; EUROPIUM IONS; FERROELECTRIC MATERIALS; ORTHORHOMBIC LATTICES; PEROVSKITE; PHASE TRANSFORMATIONS; POLYCRYSTALS; SPACE GROUPS; SPECIFIC HEAT; SPIN; STRONTIUM COMPOUNDS; TANTALATES