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Title: Metal-insulator transition in Nd{sub 1−x}Eu{sub x}NiO{sub 3}: Entropy change and electronic delocalization

The metal-insulator (MI) phase transition in Nd{sub 1–x}Eu{sub x}NiO{sub 3}, 0 ≤ x ≤ 0.35, has been investigated through the pressure dependence of the electrical resistivity ρ(P, T) and measurements of specific heat C{sub P}(T). The MI transition temperature (T{sub MI}) increases with increasing Eu substitution and decreases with increasing pressure. Two distinct regions for the Eu dependence of dT{sub MI}/dP were found: (i) for x ≤ 0.15, dT{sub MI}/dP is nearly constant and ∼−4.3 K/kbar; (ii) for x ≥ 0.15, dT{sub MI}/dP increases with x and it seems to reach a saturation value ∼−6.2 K/kbar for the x = 0.35 sample. This change is accompanied with a strong decrease in the thermal hysteresis in ρ(P, T) between the cooling and warming cycles, observed in the vicinity of T{sub MI}. The entropy change (ΔS) at T{sub MI} for the sample x = 0, estimated by using the dT{sub MI}/dP data and the Clausius-Clapeyron equation, resulted in ΔS ∼ 1.2 J/mol K, a value in line with specific heat measurements. When the Eu concentration is increased, the antiferromagnetic (AF) and the MI transitions are separated in temperature, permitting that an estimate of the entropy change due to the AF/Paramagnetic transition be carried out, yielding ΔS{sub M} ∼ 200 mJ/mol K. This value is much smaller than that expectedmore » for a s = 1/2 spin system. The analysis of ρ(P, T) and C{sub P}(T) data indicates that the entropy change at T{sub MI} is mainly due to the electronic delocalization and not related to the AF transition.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Instituto de Física, Universidade de São Paulo, CP 66318, São Paulo 05315-970 (Brazil)
  2. Departamento de Física, Centro Universitário da FEI, São Bernardo do Campo 09850-901 (Brazil)
  3. Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas, Universidade Federal do ABC, Santo André 09210-170 (Brazil)
  4. CNR-ISC, Istituto dei Sistemi Complessi, Area della Ricerca di Roma - Tor Vergata, Via del Fosso del Cavaliere 100, I-00133 Rome (Italy)
  5. Department of Physics, San Diego State University, San Diego, California 92182-1233 (United States)
Publication Date:
OSTI Identifier:
22409997
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 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; ANTIFERROMAGNETISM; CONCENTRATION RATIO; ELECTRIC CONDUCTIVITY; ENTROPY; EUROPIUM COMPOUNDS; HYSTERESIS; NEODYMIUM COMPOUNDS; NICKELATES; PARAMAGNETISM; PHASE TRANSFORMATIONS; PRESSURE DEPENDENCE; SPECIFIC HEAT; TEMPERATURE DEPENDENCE; TRANSITION TEMPERATURE