Metal-insulator transition in Nd{sub 1−x}Eu{sub x}NiO{sub 3}: Entropy change and electronic delocalization
- Instituto de Física, Universidade de São Paulo, CP 66318, São Paulo 05315-970 (Brazil)
- Departamento de Física, Centro Universitário da FEI, São Bernardo do Campo 09850-901 (Brazil)
- Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas, Universidade Federal do ABC, Santo André 09210-170 (Brazil)
- CNR-ISC, Istituto dei Sistemi Complessi, Area della Ricerca di Roma - Tor Vergata, Via del Fosso del Cavaliere 100, I-00133 Rome (Italy)
- Department of Physics, San Diego State University, San Diego, California 92182-1233 (United States)
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 expected 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.
- OSTI ID:
- 22409997
- Journal Information:
- Journal of Applied Physics, Vol. 117, Issue 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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