skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Spin-glass behavior in Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3}

Abstract

With a view to investigate the effect of small size of A-site cations on the magnetic properties of the rare earth cobaltates, Ln {sub 1-} {sub x}A{sub x} CoO{sub 3} (Ln=rare earth, A=alkaline earth), we have investigated Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3} in detail. For this purpose, we have carried out low-field DC magnetization and ac susceptibility measurements including a study of magnetic relaxation and memory effects. Both Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3} show frequency-dependent transitions at 70 and 55 K respectively in the ac susceptibility data, due to the onset of spin-glass like behavior. Their relaxation behavior exhibits aging effects. In addition, memory effects are found in the magnetization behavior. These characteristics establish spin-glass behavior in both these cobaltates, a behavior that is distinctly different from that of La{sub 0.7}Ca{sub 0.3}CoO{sub 3} and La{sub 0.5}Sr{sub 0.5}CoO{sub 3} which show well-defined ferromagnetic transitions, albeit without long-range ordering.

Authors:
 [1];  [2];  [3];  [4]
  1. Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore-560064 (India)
  2. (Sweden)
  3. Department of Engineering Sciences, Uppsala University, 751 21 Uppsala (Sweden)
  4. Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore-560064 (India). E-mail: cnrrao@jncasr.ac.in
Publication Date:
OSTI Identifier:
20784938
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 179; Journal Issue: 3; Other Information: DOI: 10.1016/j.jssc.2005.12.014; PII: S0022-4596(05)00608-0; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALKALINE EARTH METAL COMPOUNDS; CATIONS; COBALT COMPOUNDS; FREQUENCY DEPENDENCE; MAGNETIC PROPERTIES; MAGNETIZATION; RARE EARTH COMPOUNDS; RELAXATION; SPIN GLASS STATE

Citation Formats

Kundu, Asish K., Department of Engineering Sciences, Uppsala University, 751 21 Uppsala, Nordblad, P., and Rao, C.N.R. Spin-glass behavior in Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3}. United States: N. p., 2006. Web. doi:10.1016/j.jssc.2005.12.014.
Kundu, Asish K., Department of Engineering Sciences, Uppsala University, 751 21 Uppsala, Nordblad, P., & Rao, C.N.R. Spin-glass behavior in Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3}. United States. doi:10.1016/j.jssc.2005.12.014.
Kundu, Asish K., Department of Engineering Sciences, Uppsala University, 751 21 Uppsala, Nordblad, P., and Rao, C.N.R. Wed . "Spin-glass behavior in Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3}". United States. doi:10.1016/j.jssc.2005.12.014.
@article{osti_20784938,
title = {Spin-glass behavior in Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3}},
author = {Kundu, Asish K. and Department of Engineering Sciences, Uppsala University, 751 21 Uppsala and Nordblad, P. and Rao, C.N.R.},
abstractNote = {With a view to investigate the effect of small size of A-site cations on the magnetic properties of the rare earth cobaltates, Ln {sub 1-} {sub x}A{sub x} CoO{sub 3} (Ln=rare earth, A=alkaline earth), we have investigated Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3} in detail. For this purpose, we have carried out low-field DC magnetization and ac susceptibility measurements including a study of magnetic relaxation and memory effects. Both Pr{sub 0.7}Ca{sub 0.3}CoO{sub 3} and Nd{sub 0.7}Ca{sub 0.3}CoO{sub 3} show frequency-dependent transitions at 70 and 55 K respectively in the ac susceptibility data, due to the onset of spin-glass like behavior. Their relaxation behavior exhibits aging effects. In addition, memory effects are found in the magnetization behavior. These characteristics establish spin-glass behavior in both these cobaltates, a behavior that is distinctly different from that of La{sub 0.7}Ca{sub 0.3}CoO{sub 3} and La{sub 0.5}Sr{sub 0.5}CoO{sub 3} which show well-defined ferromagnetic transitions, albeit without long-range ordering.},
doi = {10.1016/j.jssc.2005.12.014},
journal = {Journal of Solid State Chemistry},
number = 3,
volume = 179,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • Perovskite cobaltites have been studied for years as some of the few solids to exhibit thermally driven spin-state crossovers. The unanticipated first-order spin and electronic transitions recently discovered in Pr-based cobaltites are notably different from these conventional crossovers, and are understood in terms of a unique valence transition. In essence, the Pr valence is thought to spontaneously shift from 3+ toward 4+ on cooling, driving subsequent transitions in Co valence and electronic/magnetic properties. Here, we apply temperature-dependent transmission electron microscopy and spectroscopy to study this phenomenon, for the first time with atomic spatial resolution, in the prototypical (Pr 0.85Y 0.15)(0.70)more » Ca 0.30CoO 3-δ. In addition to the direct spectroscopic observation of charge transfer between Pr and Co at the 165 K transition (on both the Pr and O edges), we also find a simultaneous order/disorder transition associated with O vacancies. Remarkably, the first-order valence change drives a transition between ordered and random O vacancies, at constant O vacancy density, demonstrating reversible crystallization of such vacancies even at cryogenic temperatures.« less
  • The (Pr{sub 1−y}Y{sub y}){sub 0.7}Ca{sub 0.3}CoO{sub 3} compound (y = 0.0625, T{sub MI-SS}=40 K), at the lower limit for occurrence of the first-order metal-insulator (MI) and simultaneous spin-state (SS) transitions, has been studied using electrical resistivity and magnetization measurements in magnetic fields up to 17 T. The isothermal experiments demonstrate that the low-temperature insulating phase can be destabilized by an applied field and the metallic phase returns well below the transition temperature T{sub MI-SS}. The reverse process with decreasing field occurs with a significant hysteresis. The temperature scans taken at fixed magnetic fields reveal a parabolic-like decrease in T{sub MI-SS} with increasing field strengthmore » and a complete suppression of the MI-SS transition in fields above 9 T.« less
  • Graphical abstract: Computed specific heat of (Pr{sub 1−y}Sm{sub y}){sub 0.7}Ca{sub 0.3}CoO{sub 3} (0 ≤ y ≤ 1) for the temperature range 1 K ≤ T ≤ 300 K. The curves of higher doping are shifted upward by 10 J each from the preceding curve for clarity. Highlights: ► The negative values of cohesive energy show the stability of (Pr{sub 1−y}Sm{sub y}){sub 0.7}Ca{sub 0.3}CoO{sub 3} (0 ≤ y ≤ 1) compounds. ► Our results on specific heat are in good agreement with the experimental data. ► The stability of (Pr{sub 1−y}Sm{sub y}){sub 0.7}Ca{sub 0.3}CoO{sub 3} (0 ≤ y ≤ 1) perovskitemore » increases with the Sm substitution. - Abstract: The thermodynamical and allied properties of (Pr{sub 1−y}Sm{sub y}){sub 0.7}Ca{sub 0.3}CoO{sub 3} (0 ≤ y ≤ 1) were investigated in this paper by means of a modified rigid ion model (MRIM) with pair wise interatomic interaction potential. The calculated specific heat, bulk modulus, and other thermal properties reproduce well with the available experimental data, implying that MRIM represents properly the nature of the perovskite type cobaltates. The specific heats are found to increase with temperature and decrease with concentration (y) for the present cobaltates. The increase in Debye temperature (θ{sub D}) indicates an anomalous softening of the lattice specific heat due to increase in T{sup 3}-term in the specific heat occurs with the decrease of y.« less
  • We have studied the magnetic and spin-glass (SG) properties of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} single-crystalline nanoparticles, which were prepared by the mechanical milling method with different milling times (t{sub m}). Analyzing the susceptibility data in the paramagnetic region indicates both ferromagnetic (FM) and anti-FM interactions coexisting in nanoparticles. Additionally, there is a peak associated with the freezing temperature (T{sub f}) appearing on the real part curve of the ac susceptibility, χ′(T). The T{sub f} value increases with increasing frequency as expected for SG systems. The SG behavior was also checked by using the criterion parameter c = ΔT{sub f}/T{sub f}Δ(log{sub 10}f), andmore » the power law τ = τ{sub 0}(T/T{sub g} − 1){sup −zν}. The obtained values of c ≈ 5 × 10{sup −2}, τ{sub 0} ≈ 10{sup −5} s and zν ≈ 2–3 are consistent with those expected for SG-like systems, suggesting an existence of a SG phase transition at T{sub g} below T{sub f}, which decreases with decreasing 〈D〉. Basing on ln(f) versus T{sub f} data, and the Néel-Arrhenius model [ln(f) = ln(f{sub 0}) - E{sub a}/k{sub B}T] and Vogel–Fulcher law [ln(f) = ln(f{sub 0}) - E{sub a}/k{sub B}(T - T{sub 0})], the Larmor frequency (f{sub 0}), activation energy (E{sub a}) and effective temperature (T{sub 0}) for the samples with different 〈D〉 were determined. Obtained results indicate the existence a strong interaction between nanoparticles.« less
  • There are different models which to try to explain the transport properties of the manganese oxides in terms of magnetic polarons, Zener double exchange and Jahn-Teller distortions of the lattice which is temperature dependent. Using Rutherford backscattering techniques (2{endash}3 MeV He ions) we are measuring the presence of lattice distortions by studying the angular scans in the channeling mode. The angular widths (FWHM) can be used to extract both dynamic and static displacements of the atoms from their equilibrium sites. The technique is extremely powerful in the sense that {ital local} {ital uncorrected} displacements as small as 0.01 A frommore » the equilibrium position can be detected. The extraction of the physics from the data is relatively straight forward compared to other techniques such as XRD or neturon scattering. Using a variable temperature backscattering system at our center (one of three or four systems around the world) the angular width (FWHM) is found to exhibit a dramatic change with temperature increasing with decreasing temperature showing a possible correlation with both the transport and magnetic properties. The results suggest a decrease in the lattice disorder with reduced temperature far in excess of what one would predict on the basis of a simple Debye behavior. The reduction in the lattice disorder correlates very well with the resistance vs temperature dependence. A variety of manganese oxide epitaxial thin films grown by pulsed laser deposition have been studied and the data suggests a role for structural distortions in any mechanism to explain the transport properties of these materials. {copyright} {ital 1996 American Institute of Physics.}« less