Structure, electron-transport properties, and giant magnetoresistance of hole-doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">LaMnO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>systems

Mahendiran, R.; Tiwary, Satish K.; Raychaudhuri, A. K.; Ramakrishnan, T. V.; Mahesh, R.; Rangavittal, N.; Rao, C. N. R.

doi:10.1103/physrevb.53.3348

Cited by 526 publications

(278 citation statements)

References 37 publications

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“…Their concentration depends on the exact preparation conditions, especially the sintering temperature and oxygen partial pressure. It was shown by Tamura et al 20 that for xϭ0.2 the vacancy concentration increases markedly only for extremely small oxygen partial pressures below 10 Ϫ2 Pa at 1473 K. Mahendiran et al 21 show that the vacancy concentration is bigger for smaller x. Nevertheless, for small amounts of ''self-doping'' the spin entropy is unaffected, since it is determined by the ratio of the spin degeneracies and is independent of the doping concentration.…”

Section: Sϭ Kmentioning

confidence: 99%

Transport mechanisms in dopedLaMnO3:Evidence for polaron formation

Palstra

Ramirez²,

Cheong³

et al. 1997

Phys. Rev. B

171

103

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We report electrical transport experiments on the colossal magnetoresistance compound (La,Ca͒MnO 3 over a wide range of composition and temperature. Comparison of thermopower and electrical resistivity measurements above the metal-insulator transition indicate a transport mechanism not dominated by spin disorder, but by small polaron formation. Additionally, we find that in the high-temperature limit the thermopower corresponds to backflow of spin entropy, expected from motion of positively charged particles in a rigid Sϭ2 system, showing a remarkable independence of Sϭ3/2 particle density. ͓S0163-1829͑97͒09334-X͔The recent observation of large magnetoresistance effects in thin films of doped LaMnO 3 has renewed the interest in the metal-insulator transition in these materials. [1][2][3] Since the metal-insulator transition temperature, T MI , can be tuned to above room temperature, this opens possibilities to use this material not only for recording media but also for other types of magnetic switching applications. However, the emerging notion that magnetoresistance due to a metal-insulator transition decreases with increasing T MI , necessitates a better understanding of the underlying basic transport mechanism to exploit the magnetoresistive properties of these materials fully. The microscopic nature of the transport mechanism is condensed into the description of double exchange, the simultaneous electron transfer of an electron on a Mn atom to an O atom of the surrounding oxygen octahedron, and another electron from this O atom to a neighboring Mn atom. 4 This indirect exchange mechanism establishes, because of spin conservation in the exchange, a direct relation of the metallic state with the ferromagnetic coupling between the Mn spins. However, there is remarkably little known about the transport mechanism in the insulating state. Whereas spin disorder can contribute to the variations in the resistivity near T c , only more recently the role of electron-phonon interactions on the localization has been put in a clearer perspective. [5][6][7] This theoretical work was based on research on magnetic semiconductors like EuO, and only recently applied to doped LaMnO 3 . Still, it is not known if the metal insulator transition in doped LaMnO 3 is driven by changes in the carrier density or the mobility.In order to gain insight into the nature of the transport mechanism, we have performed thermopower measurements on doped LaMnO 3 over a wide range of concentrations and temperatures in addition to the basic characterization by electrical resistivity and magnetic measurements. Thermopower is in contrast to electrical resistivity relatively insensitive to effects of grain boundaries and disorder. We will show that for this material, thermopower provides unique insight into the transport mechanism. First, we show that the change of sign in the thermopower is not related to competition between electron and hole conduction, but accidental cancellation of the entropic term and the energy transport term of the thermopower...

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Section: Sϭ Kmentioning

confidence: 99%

Transport mechanisms in dopedLaMnO3:Evidence for polaron formation

Palstra

Ramirez²,

Cheong³

et al. 1997

Phys. Rev. B

171

103

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show abstract

“…This angle is expected to be close to 180 • for these materials [18]. The amplitude reduction factor [7,18,19]. Fits to the Mn-O broadening parameter for these data are presented in Mn-Ca signal could vary widely in the fits; interferences occur which make various combinations possible.…”

mentioning

confidence: 99%

“…In particular, the Mn-O-Mn bond angle was taken to be 180 • , even though for some compounds in the LaMnO 3 series, this angle can be as small as 160 • . This angle is expected to be close to 180 • for these materials [18]. The amplitude reduction factor [7,18,19].…”

mentioning

confidence: 99%

Evidence of magnetization-dependent polaron distortion inLa1−xAxMn
Booth
¹
,
Bridges
²
,
Snyder
³

et al. 1996
Phys. Rev. B
83
12
57
0
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“…However, the polaron formation energy ranges from 110 to 160 meV in La 1-x Ca x MnO 3 (0 B x B 0.5) and ranges from 50 to 110 meV in La 1- [74][75][76]. The deduced value of the E p lies between above range and it reveals that addition of K increases the carrier density.…”

Section: Discussion and Analysis Of Resultsmentioning

confidence: 99%

Metallic and semi-conducting resistivity behaviour of La0.7Ca0.3−x K x MnO3 (x = 0.05, 0.1) manganites

Varshney

Dodiya

2014

J Theor Appl Phys

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The temperature dependence of electrical resistivity, q, of ceramic La 0.7 Ca 0.3-x K x MnO 3 (x = 0.05, 0.1) is investigated in metallic and semi-conducting phase. The metallic resistivity is attributed to be caused by electron-phonon, electron-electron and electron-magnon scattering. Substitutions affect average mass and ionic radii of A-site resulting in an increase in Debye temperature h D attributed to hardening of lattice with K doping. The optical phonon modes shift gradually to lower mode frequencies leading to phonon softening. Estimated resistivity compared with reported metallic resistivity, accordingly q diff. = [q exp. -{q 0 ? q e-ph (=q ac ? q op )}], infers electron-electron and electron-magnon dependence over most of the temperature range. Semi-conducting nature is discussed with variable range hopping and small polaron conduction model. The decrease in activation energies and increase in density of states at the Fermi level with enhanced Ca doping is consistently explained by cationic disorder and Mn valence.

show abstract

Structure, electron-transport properties, and giant magnetoresistance of hole-dopedLaMnO3systems

Cited by 526 publications

References 37 publications

Transport mechanisms in dopedLaMnO3:Evidence for polaron formation

Transport mechanisms in dopedLaMnO3:Evidence for polaron formation

Evidence of magnetization-dependent polaron distortion inLa1−xAxMn
Booth
¹
,
Bridges
²
,
Snyder
³

et al. 1996
Phys. Rev. B
83
12
57
0
View full text Add to dashboard Cite

Metallic and semi-conducting resistivity behaviour of La0.7Ca0.3−x K x MnO3 (x = 0.05, 0.1) manganites

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Structure, electron-transport properties, and giant magnetoresistance of hole-dopedLaMnO3systems

Cited by 526 publications

References 37 publications

Transport mechanisms in dopedLaMnO3:Evidence for polaron formation

Transport mechanisms in dopedLaMnO3:Evidence for polaron formation

Evidence of magnetization-dependent polaron distortion inLa1−xAxMnBooth1, Bridges2, Snyder3 et al. 1996Phys. Rev. B8312570View full textAdd to dashboardCite

Metallic and semi-conducting resistivity behaviour of La0.7Ca0.3−x K x MnO3 (x = 0.05, 0.1) manganites

Contact Info

Product

Resources

About

Evidence of magnetization-dependent polaron distortion inLa1−xAxMn
Booth
¹
,
Bridges
²
,
Snyder
³

et al. 1996
Phys. Rev. B
83
12
57
0
View full text Add to dashboard Cite