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Title: Magnetocaloric properties of distilled gadolinium: Effects of structural inhomogeneity and hydrogen impurity

High-purity Gd prepared by distillation is a structurally inhomogeneous system consisting of needle-shaped crystals of cross section 0.5–2.5 μm with near-c-axis orientation embedded in a matrix of nanosized (30–100 nm) grains. By measuring the magnetocaloric effect (MCE) directly, we find that the MCE values differ markedly for the plate-shaped samples cut out of a distillate along and perpendicular to the crystals. The effect of small controlled amounts of impurity (hydrogen) on the properties of distilled Gd is further studied. We observe opposite trends in the MCE response to hydrogen charging with respect to the crystal's orientation within the samples and discuss mechanisms interrelating the unique structural morphology with the impurity behavior. As an overall assessment, the Curie temperatures of α-GdH{sub x} solid solutions increase from 291 K up to 294 K when increasing hydrogen concentration x from 0 to 0.15. Hydrogenation is found to broaden the ferromagnetic-to-paramagnetic phase transition. Hydrogen-containing specimens demonstrate reversibility of MCE at these temperatures.
Authors:
; ; ;  [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [1] ;  [3] ; ;  [5] ; ;  [6]
  1. Baikov Institute of Metallurgy and Materials Science RAS, 119991 Moscow (Russian Federation)
  2. Institute of Physics ASCR, 18221 Prague (Czech Republic)
  3. (Poland)
  4. (Russian Federation)
  5. Institute of Low Temperature and Structure Research PAS, 50-950 Wroclaw (Poland)
  6. Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, 12116 Prague (Czech Republic)
Publication Date:
OSTI Identifier:
22299897
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 24; 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; CHARGES; CROSS SECTIONS; CRYSTALS; CURIE POINT; DISTILLATION; GADOLINIUM; HYDROGEN ADDITIONS; HYDROGENATION; IMPURITIES; MAGNETIC PROPERTIES; NANOSTRUCTURES; PARAMAGNETISM; PHASE TRANSFORMATIONS; SOLID SOLUTIONS