The surface terminal layer and composition of the colossal magnetoresistance perovskite: La0.65Pb0.35MnO3

Abstract

The composition in the surface region of the colossal magnetoresistance perovskite manganite materials, La 0.65 Pb 0.35 MnO 3 has been studied using angle resolved x-ray photoemission spectroscopy. The results are consistent with a Mn-O terminal layer and Pb segregation to the near-surface region. This is similar to the behavior exhibited by La 0.

Origin of the magnetic moments in La0.65Pb0.35MnO3 epitaxial thin films

“…1, the L 2,3 edges are very well defined and exhibit sharp peaks. These spectra are comparable with the Mn 2p core levels obtained using x-ray photoemission spectroscopy, 6 which can only probe 5-15 Å from the surface. The conclusion here is that the sample is relatively free of defects and homogenous, except in the surface region, which is compositionally different from the bulk.…”

“…This deviation can be attributed to compositional differences at the surface boundary layer. 6 In Fig. 3͑b͒ we show the temperature dependence of the O 1s XAS spectra of La 0.65 Pb 0.35 MnO 3 single-crystal thin film.…”

“…The conclusion here is that the sample is relatively free of defects and homogenous, except in the surface region, which is compositionally different from the bulk. The surface region, discussed in detail elsewhere, 6 The magnetization of the bulk measured with a superconducting quantum interference device ͑SQUID͒ is shown in Fig. 2͑a͒.…”

Interface effects in spin-polarized metal/insulator layered structures

“…There is a strong chemical potential for surface segregation in the postulated half-metallic ferromagnetic materials [245,246] that results in equilibrium surfaces at elevated temperatures that are not the same stoichiometry as the bulk. Evidence of the resulting surface segregation has been found for NiMnSb(001) [245,176,[247][248][249], TiCoSb [248,249] and the manganese perovskites La 1-x A x MnO 3 (A=Ca, Sr, Pb) [246,[250][251][252][253][254][255][256][257]. The extent of segregation can be considerable once equilibrium is established and extends from the surface well into the bulk; it need not be localized just to the surface layer.…”

The polarization of Sb overlayers on NiMnSb(100)

“…The spectra for two opposite helicities were recorded by alternating the magnetization at every photon energy. In total electron yield mode, the XAS spectrå probes approximately 20 clean surface, when attenuation by the Sb overlayer is minimized.…”