Effect of annealing temperature on local distortion ofLa0.67Ca0.33MnO<

Abstract

Mn K-edge fluorescence data are presented for thin film samples (3000Å) of Colossal Magnetoresistive (CMR) La 0.67 Ca 0.33 MnO 3 : as-deposited, and post-annealed at 1000 K and 1200 K. The local distortion is analyzed in terms of three contributions: static, phonon, and an extra, temperature-dependent, polaron term. The polaron distortion is very small for the as-deposited sample and increases with the annealing temperature. In contrast, the static distortion in the samples decreases with the annealing temperature. Although the local structure of the as-deposited sample shows very little temperature dependence, the change in resistivity with temperature is the largest of these three thin film samples. The as-deposited sample also has the highest magnetoresistance (MR), which indicates some other mechanism may also contribute to the transport properties of CMR samples. We also discuss the relationship between local distortion and the magnetization of the sample.

Changes in the local structure of aLa0.70Ca0.30MnO3Cao1, Bridges2, Booth3 et al. 2000Phys. Rev. BSelf Cite11070View full textAdd to dashboardCite

“…28͒ with the quantity S 0 2 N fixed at 4.3, based on earlier work. 17,18,20 In these fits, only and r were varied. The value of 2 for the Mn-O peak was obtained for each temperature and magnetic field.…”

“…Here T 2 is a measure of the phonon contribution ͑the DebyeWaller contribution͒, FP 2 is the full polaronlike distortion obtained at high temperature, which is defined as the difference between data 2 and T 2 at high temperatures ͑above T c ), and data 2 is extracted from fits of the XAFS data, 18,20 for the Mn-O peak. ⌬ 2 is zero above T c and ln(⌬ 2 ) increases linearly as the sample's magnetization increases.…”

“…[14][15][16] Over the last few years such distortions have been observed, and the character and magnitude of these distortions as a function of temperature have now been welldocumented by x-ray absorption fine structure ͑XAFS͒ experiments and by pair distribution analysis of neutron diffraction data in some colossal magnetoresistive ͑CMR͒ systems. [17][18][19][20][21][22][23] Such measurements, obtained at zero magnetic field, show that the amplitude of the Mn-O pair distribution peak decreases rapidly with T, for temperatures just below T c . This change can be modeled as a rapid increase in , the width of the pair distribution function, over this temperature range.…”

Correlated Local Atomic Displacements: The Microscopic Origins for Macroscopic Phenomena.

“…When polarons form there is a large additional increase in the local distortions about a lattice site, generally referred to as a Jahn-Teller (JT) distortion [3,8,9,10,11,12]. This distortion enhances the increase in resistivity as the sample becomes paramagnetic [13,14,15].…”

Role of growth temperature and oxygen partial pressure on the structural and electrical properties of pulsed laser deposited La1−xSrxnO3−δ thin films

“…The ferromagnetism of LSMO can be tuned by varying the doping concentration and oxygen content [9][10][11]. By varying the deposition temperature and oxygen partial pressure, the oxygen content in LSMO thin films can be controlled [12][13][14]. Also the oxygen partial pressure during deposition plays a very crucial role in shaping the microstructure and surface morphology and hence the interface quality of the thin film [15].…”