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Title: Possible experimental signature of charge-orbital density waves in Nd{sub 1-x}Ca{sub 1+x}MnO{sub 4}: Heat capacity and magnetization study

Abstract

Single crystals of Nd{sub 1-x}Ca{sub 1+x}MnO{sub 4} have been prepared by the traveling floating-zone method, and possible evidence of a charge-orbital density wave in this material was presented earlier [Phys. Rev. B 68, 092405 (2003)] using high-resolution electron microscopy and electron diffraction. We present possible further evidence of charge-orbital ordering in this material using heat capacity measurements. Our heat capacity measurements indicate a clear transition consistent with prior observation. We find two main transitions, one at temperature T{sub H}{sup HC}=310-314 K and other in the vicinity of T{sub A}{sup HC}=143 K. In addition, we may also conclude that there is a strong electron-phonon coupling in this material. In order to further study and confirm these anomalies we have performed dc magnetization measurements. The dc magnetic measurements confirm these two transitions. Again, we find two main transitions, one at temperature T{sub H}{sup M}=318-323 K and other at around T{sub A}{sup M}=164 K.

Authors:
; ; ;  [1]; ;  [2];  [3]
  1. AML, NIMS, Tsukuba 305-0044, Ibaraki (Japan)
  2. Crystal Group, Yamanashi University, Yamanashi (Japan)
  3. Department of Physics, Bahauddin Zakariya University, Multan (Pakistan)
Publication Date:
OSTI Identifier:
21045875
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 20; Other Information: DOI: 10.1103/PhysRevB.75.205134; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CALCIUM COMPOUNDS; CHARGE DENSITY; DENSITY; ELECTRON DIFFRACTION; ELECTRON-PHONON COUPLING; MAGNETIZATION; MANGANATES; MONOCRYSTALS; NEODYMIUM COMPOUNDS; SPECIFIC HEAT; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K; TRANSMISSION ELECTRON MICROSCOPY; ZONE MELTING

Citation Formats

Alam, Sher, Nagai, T., Xu, M., Matsui, Y., Islam, A. T. M. N., Tanaka, I., and Ahmad, Javed. Possible experimental signature of charge-orbital density waves in Nd{sub 1-x}Ca{sub 1+x}MnO{sub 4}: Heat capacity and magnetization study. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.205134.
Alam, Sher, Nagai, T., Xu, M., Matsui, Y., Islam, A. T. M. N., Tanaka, I., & Ahmad, Javed. Possible experimental signature of charge-orbital density waves in Nd{sub 1-x}Ca{sub 1+x}MnO{sub 4}: Heat capacity and magnetization study. United States. doi:10.1103/PHYSREVB.75.205134.
Alam, Sher, Nagai, T., Xu, M., Matsui, Y., Islam, A. T. M. N., Tanaka, I., and Ahmad, Javed. Tue . "Possible experimental signature of charge-orbital density waves in Nd{sub 1-x}Ca{sub 1+x}MnO{sub 4}: Heat capacity and magnetization study". United States. doi:10.1103/PHYSREVB.75.205134.
@article{osti_21045875,
title = {Possible experimental signature of charge-orbital density waves in Nd{sub 1-x}Ca{sub 1+x}MnO{sub 4}: Heat capacity and magnetization study},
author = {Alam, Sher and Nagai, T. and Xu, M. and Matsui, Y. and Islam, A. T. M. N. and Tanaka, I. and Ahmad, Javed},
abstractNote = {Single crystals of Nd{sub 1-x}Ca{sub 1+x}MnO{sub 4} have been prepared by the traveling floating-zone method, and possible evidence of a charge-orbital density wave in this material was presented earlier [Phys. Rev. B 68, 092405 (2003)] using high-resolution electron microscopy and electron diffraction. We present possible further evidence of charge-orbital ordering in this material using heat capacity measurements. Our heat capacity measurements indicate a clear transition consistent with prior observation. We find two main transitions, one at temperature T{sub H}{sup HC}=310-314 K and other in the vicinity of T{sub A}{sup HC}=143 K. In addition, we may also conclude that there is a strong electron-phonon coupling in this material. In order to further study and confirm these anomalies we have performed dc magnetization measurements. The dc magnetic measurements confirm these two transitions. Again, we find two main transitions, one at temperature T{sub H}{sup M}=318-323 K and other at around T{sub A}{sup M}=164 K.},
doi = {10.1103/PHYSREVB.75.205134},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 20,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Pr{sub 1-x}Ca{sub x}MnO{sub 3} in the doping range between 0.3<x<0.5 represent an extremely interesting manganite system for the study of the interplay of different kinds of ordering (charge, orbital, lattice, and spin). While there is consensus that a charge- and orbital-ordered state develops below a transition temperature T{sub co}{approx_equal}230 K, recent controversial structural refinements resulting from neutron and x-ray diffraction studies challenged our understanding of the particular type of charge ordering (CO) and orbital ordering (OO), and consequently, the underlying mechanism of the colossal resistance effects. Here, we present a detailed high-resolution transmission electron microscopy and electron-diffraction study that, basedmore » on extinction rules, resolves the current controversy and confirms the existence of the Zener-polaron (ZP)-type CO and/or OO in Pr{sub 1-x}Ca{sub x}MnO{sub 3}. The ZP-type ordering is further verified by atomic-column-resolved electron energy-loss spectroscopy revealing strong charge ordering of the in-plane oxygen-Mn bonds, while valence disproportionation at the Mn sites is less than expected. Over wide doping and temperature ranges, we observed structural phase coexistence between the ZP-CO/OO P2{sub 1}nm and the disordered Pbnm structure.« less
  • We study and compare magnetic and electron paramagnetic resonance behaviors of bulk and nanoparticles of Nd{sub 1−x}Ca{sub x}MnO{sub 3} in hole doped (x=0.4;NCMOH) and electron doped (x=0.6;NCMOE) samples. NCMOH in bulk form shows a complex temperature dependence of magnetization M(T), with a charge ordering transition at ∼250 K, an antiferromagnetic (AFM) transition at ∼150 K, and a transition to a canted AFM phase/mixed phase at ∼80 K. Bulk NCMOE behaves quite differently with just a charge ordering transition at ∼280 K, thus providing a striking example of the so called electron-hole asymmetry. While our magnetization data on bulk samples are consistent with the earliermore » reports, the new results on the nanoparticles bring out drastic effects of size reduction. They show that M(T) behaviors of the two nanosamples are essentially similar in addition to the absence of the charge order in them thus providing strong evidence for vanishing of the electron-hole asymmetry in nanomanganites. This conclusion is further corroborated by electron paramagnetic resonance studies which show that the large difference in the “g” values and their temperature dependences found for the two bulk samples disappears as they approach a common behavior in the corresponding nanosamples.« less
  • The interpretation given in our recent x-ray scattering study of Pr{sub 1-x}Ca{sub x}MnO{sub 3} in terms of charge and orbital ordering is questioned in the preceding Comment by Garcia and Subias. They argue that anisotropy of the charge distribution induced by local distortions gives rise to the so-called charge order reflections. In this Reply we suggest that the two different pictures are reconcilable.
  • No abstract prepared.
  • No abstract prepared.