Effects of Ru substitution for Mn on La0.7Sr0.3MnO3 perovskites

Wang, Li Min; Lai, Jiing Yih; Wu, J. B.; Kuo, Y. K.; Chang, C. L.

doi:10.1063/1.2761690

Cited by 51 publications

(28 citation statements)

References 40 publications

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“…The results for the parent compound suggest some sort of inhomogeneity or partial canted spin in the FM state. 26 This situation is abundant in most of polycrystalline LCMO. 27 With Cr substitution the observed entropy change ͑⌬S͒ near the transition temperature decreases sharply and only a small fraction of the theoretical entropy is observed.…”

Section: E Specific Heatmentioning

confidence: 99%

Structural, electrical, magnetic, and thermal studies of Cr-doped La0.7Ca0.3Mn1−xCrxO3 (≤x≤1) manganites

Kumar¹,

Kishan²,

Rao

et al. 2010

Journal of Applied Physics

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We report detailed structural, electrical, magnetic, and specific heat studies on La 0.7 Ca 0.3 Mn 1−x Cr x O 3 manganites. Rietveld analysis of fitted and observed x-ray diffraction patterns exhibited the single-phase nature of all the studied materials, which crystallize in Pbnm space group. Successive substitution of Cr at Mn-site in La 0.7 Ca 0.3 Mn 1−x Cr x O 3 manganites increases the electrical resistivity and decreases the characteristic insulator-metal transition temperature ͑T IM ͒ of the parent compound along with a humplike feature for higher Cr-content ͑x Ͼ 0.06͒ samples. The hump structure basically signifies the onset of antiferromagnetic ͑AFM͒ interactions as inferred by both the magnetic and infrared ͑IR͒ spectroscopy studies. The systematic suppression of FM state results in a spin glass ͑SG͒-like behavior. IR studies revealed that the vibration mode at 413 cm −1 being associated with internal bending of MnO 6 octahedra, becomes softer, indicating an increase in distortion and hence the possible SG behavior. The critical exponents ͑␣, ␤, and ␥͒ are calculated from the heat capacity ͑C P ͒ data near the T IM / T FM . The same exhibited variations of their values with doping. In particular, the value of ␤ increases from 0.37͑x = 0.0͒ to 0.43͑x = 0.04͒, clearly indicating the coexistence of both long and short range magnetic orders, i.e., tendency toward SG state for Cr-doped samples. On the basis of present results, it is suggested that Cr dilutes double-exchange based FM and rather promotes the AFM based superexchange interactions via Cr 3+ / Mn 4+ ions. Substitution of Cr systematically destroys both the metallic state and long range FM order.

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Section: E Specific Heatmentioning

confidence: 99%

Structural, electrical, magnetic, and thermal studies of Cr-doped La0.7Ca0.3Mn1−xCrxO3 (≤x≤1) manganites

Kumar¹,

Kishan²,

Rao

et al. 2010

Journal of Applied Physics

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“…The measured data are in accord with the earlier reported results. 32,34 Below T P , a pronounced peak at 276 K is noticed. The transition temperature, defined as the peak position, being lower than the corresponding I-M transition temperature T P reflects that the specific heat anomaly is related to the magnetic ordering in the sample due to paramagnetic-FM transition ͓Fig.…”

Section: S͑t͒mentioning

confidence: 99%

“…The magnitude of ͑T͒, typically of amorphous materials, 29 lies in the range of 16-42 mW/ cm K in the temperature range of study, and is consistent with other reported values. [30][31][32] For a crystalline solid, such low value of thermal conductivity can be thought to originate from random, noncentral distortions of the lattice, resulting in high degree of disorder. In manganites, such a scenario may be attributed to the JT distortions of the Mn +3 O 6 octahedra.…”

Section: S͑t͒mentioning

confidence: 99%

Magnetotransport, thermoelectric power, thermal conductivity and specific heat of Pr2/3Sr1/3MnO3 manganite

Panwar

Rao

Singh

et al. 2008

Journal of Applied Physics

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Magnetotransport and thermal studies of Pr 2/3 Sr 1/3 MnO 3 polycrystalline sintered bulk sample are reported here. The resistivity ͑T͒ and thermoelectric power S͑T͒ data show an insulator to metal ͑I-M͒ phase transition at T P Ϸ 294 K and T S Ϸ 290 K, respectively. Magnetization measurement confirms that the sample undergoes a transition from paramagnetic to ferromagnetic phase at a defined Curie temperature T C = 280 K. A substantial increase in magnetoresistance from 2.5% at 280 K to 5% at 77 K has been noticed in a low magnetic field 0.15 T. Small polaron hopping model is found to be operative above the transition temperature T P , whereas electron-electron and electron-magnon scattering processes govern the low temperature metallic behavior. A detailed analysis of thermoelectric power in the ferromagnetic regime suggests that the complicated temperature dependence of S may be understood on the basis of electron-magnon scattering. A transition from decreasing high temperature thermal conductivity ͑due to local anharmonic distortions associated with small polarons͒, to an increasing thermal conductivity ͑due to decreasing of phonon-phonon scattering͒ and thereafter a peak at ϳ100 K ͑signifying a crossover from Umklapp to defect-limited scattering͒ have also been noticed. Specific heat measurements depict a pronounced anomaly near the T C , indicating the magnetic ordering and magnetic inhomogeneity in the sample.

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“…These systems have further renovated interest of condense matter community due to the observed novel phenomenon's like colossal magnetoresistance (CMR), metal-insulator (MI) and charge ordering (CO), in manganites [6][7][8]. The underlying physics of those phenomena has been interpreted in terms of the double exchange (DE) model, in which a strong exchange interaction occurs between Mn 3+ and Mn 4+ ions through intervening filled oxygen 2p states [9], Jahn-Teller (JT) polaron, and tolerance factor [10]. The knowledge of the crystal structure and the chemical bonding of these compounds are of capital importance to the understanding of the peculiar magnetotransport properties in these perovskites.…”

Section: Introductionmentioning

confidence: 99%