Charge/orbital ordering structure and microstructure of Pr1−xCaxMnO3 (x⩽0.5) studied by low-temperature TEM

Asaka, Toru; Tsutsumi, Sadao; Yamada, Shigeki; Arima, T.; Tsuruta, Chusei; Kimoto, Koji; Matsui, Y.

doi:10.1016/s0921-4534(01)00236-2

Cited by 4 publications

(4 citation statements)

References 17 publications

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“…Because neither the CAF nor FM densities-of-states contain a gap, both phases are metallic within the DEV model for t > 0. Due to short-range orbital ordering, a CDW with the same period as the one predicted here has in fact been observed in the AFM regions of Pr 0.7 Ca 0.3 MnO 3 [7,29]. However, the observed charge ordering is perfect: all of the Mn 3+ ions lie on one sublattice and all of the Mn 4+ ions lie on the other.…”

Section: Ground-state Properties Of the Dev Modelsupporting

confidence: 73%

“…Since CE-type AFM ordering occurs at half-filling, the local charge ordering observed in the manganites Pr 0.6 Ca 0.4 MnO 3 [7,29] and La 0.7 Ca 0.3 MnO 3 [2,3] would be simplified if the polaronic regions were rich in holes and poor in electrons compared to the bulk. Our model provides a natural explanation for this behaviour, since the electronic fraction on b sites is substantially smaller than the fraction on a sites as the electrons avoid regions with more pronounced AFM order.…”

Section: Discussionmentioning

confidence: 99%

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Double exchange in a magnetically frustrated system

Fishman¹

2004

J. Phys.: Condens. Matter

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This work examines the magnetic order and spin dynamics of a double-exchange model with competing ferromagnetic and antiferromagnetic Heisenberg interactions between the local moments. The Heisenberg interactions are periodically arranged in a Villain configuration in two dimensions with nearest-neighbor, ferromagnetic coupling J and antiferromagnetic coupling −ηJ. This model is solved at zero temperature by performing a 1/ √ S expansion in the rotated reference frame of each local moment. When η exceeds a critical value, the ground state is a magnetically frustrated, canted antiferromagnet. With increasing hopping energy t or magnetic field B, the local moments become aligned and the ferromagnetic phase is stabilized above critical values of t or B. In the canted phase, a charge-density wave forms because the electrons prefer to sit on lines of sites that are coupled ferromagnetically. Due to a change in the topology of the Fermi surface from closed to open, phase separation occurs in a narrow range of parameters in the canted phase. In zero field, the long-wavelength spin waves are isotropic in the region of phase separation. Whereas the average spin-wave stiffness in the canted phase increases with t or η, it exhibits a more complicated dependence on field. This work strongly suggests that the jump in the spin-wave stiffness observed in Pr 1−x Ca x MnO 3 with 0.3 ≤ x ≤ 0.4 at a field of 3 T is caused by the delocalization of the electrons rather than by the alignment of the antiferromagnetic regions.

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Section: Ground-state Properties Of the Dev Modelsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Double exchange in a magnetically frustrated system

Fishman¹

2004

J. Phys.: Condens. Matter

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“…To explain the modification of the arrangement of spins along the c-axis, Jirak et al [66] postulated that the extra 3z 2 -r 2 electrons hop along the c-axis mediating the ferromagnetic DE interaction. In fact, the one-dimensional ordering of the 3z 2 -r 2 electrons along the c axis (z direction) has been confirmed by the transmission electron microscopy on Pr 1−x Ca x MnO 3 (x = 3/8 = 0.375) [68], in which the extra electron density, one per four Mn 4+ -sites, becomes commensurate. Such an effect of extra electrons on the magnetic structure should be enhanced with the decrease of x from 0.5.…”

Section: Magnetic Field Effects On Charge-orbital Orderingmentioning

confidence: 82%

Critical features of colossal magnetoresistive manganites

2006

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Colossal magnetoresistance (CMR) phenomena are observed in the perovskite-type hole-doped manganites in which the double-exchange ferromagnetic metal phase and the charge-orbital ordered antiferromagnetic phase compete with each other. The quenched disorder arising from the inherent chemical randomness or the intentional impurity doping may cause major modifications in the electronic phase diagram as well as in the magnetoelectronic properties near the bicritical point that is formed by such a competition of the two phases. One is the phase separation phenomenon on various timescales (from static to dynamic) and on various length-scales (from glass-like nano to grain-like micron). The other is the enhanced phase fluctuation with anomalous reduction in the transition temperatures of the competing phases (and hence in the bicritical-point temperature). The highly effective suppression of such a phase fluctuation by an external magnetic field is assigned here to the most essential ingredient of the CMR physics. Such profound and dramatic features as appearing in the bicritical region are extensively discussed in this paper with ample examples of the material systems specially designed for this purpose. The unconventional phase-controls over the competing phases in terms of magnetic/electric fields and photo-excitations are also exemplified.

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“…Nevertheless, the thermopower studies carried out by Yamada et al [10] for x ∼ 0.35 and the evidence for a charge gap in the optical absorption for the polarization at x ∼ 0.40 described by Okitomo et al [11] suggest that the magnetic properties in this domain should not vary so continuously versus x. This viewpoint is reinforced by the recent discovery of a new kind of OO-CO ordering for x = 3/8 by Asaka et al [12].…”

Section: Introductionmentioning

confidence: 94%

Ga and Ba substitution in charge ordered Pr_1 xCa_xMnO₃: exceptional predisposition of thex= 0.43 compound to ferromagnetism

Zhu¹,

Raveau²,

Hardy³

et al. 2004

J. Phys.: Condens. Matter

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The effect of low substitution levels of Ga for Mn and of Ba for Ca upon the magnetic properties of orbital-charge ordered manganites has been studied for 0.33 < x 0.50 in Pr 1−x Ca x MnO 3 . It is shown that, for very small Ga or Ba contents (∼2%), a ferromagnetic ground state can be created. More importantly, the ferromagnetic fraction, very small for x ≈ 0.37-0.33 and x = 0.50, goes abruptly through a maximum for the x ≈ 0.43 compound, which can be considered as a full ferromagnet at 2.5 K, with ferromagnetic fractions of 95-100% for 2-3% Ba. The role of the local 'counter-distortion' introduced by Ga or Ba in the appearance of ferromagnetism is discussed in the context of orbital-charge ordering and phase separation.

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Charge/orbital ordering structure and microstructure of Pr1−xCaxMnO3 (x⩽0.5) studied by low-temperature TEM

Cited by 4 publications

References 17 publications

Double exchange in a magnetically frustrated system

Double exchange in a magnetically frustrated system

Critical features of colossal magnetoresistive manganites

Ga and Ba substitution in charge ordered Pr_1 xCa_xMnO₃: exceptional predisposition of thex= 0.43 compound to ferromagnetism

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Charge/orbital ordering structure and microstructure of Pr1−xCaxMnO3 (x⩽0.5) studied by low-temperature TEM

Cited by 4 publications

References 17 publications

Double exchange in a magnetically frustrated system

Double exchange in a magnetically frustrated system

Critical features of colossal magnetoresistive manganites

Ga and Ba substitution in charge ordered Pr1 xCaxMnO3: exceptional predisposition of thex= 0.43 compound to ferromagnetism

Contact Info

Product

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Ga and Ba substitution in charge ordered Pr_1 xCa_xMnO₃: exceptional predisposition of thex= 0.43 compound to ferromagnetism