Abstract
Quantum interference effects (QIEs) dominate the appearance of low-temperature resistivity minimum in colossal magnetoresistance manganites. The T1/2 dependent resistivity under high magnetic field has been evidenced as electron-electron (e-e) interaction. However, the evidence of the other source of QIEs, weak localization (WL), still remains insufficient in manganites. Here we report on the direct experimental evidence of WL in QIEs observed in the single-crystal La0.7Sr0.3MnO3 (LSMO) ultrathin films deposited by laser molecular beam epitaxy. The sharp cusps around zero magnetic field in magnetoresistance measurements is unambiguously observed, which corresponds to the WL effect. This convincingly leads to the solid conclusion that the resistivity minima at low temperatures in single-crystal manganites are attributed to both the e-e interaction and the WL effect. Moreover, the temperature-dependent phase-coherence length corroborates the WL effect of LSMO ultrathin films is within a two-dimensional localization theory.
Highlights
IntroductionVast phenomenological analyses have been fitted to prove the existence of the weak localization (WL) effect[2,11,12], the typical WL effect in magnetoresistance (MR) measurements, i.e., the sharp cusps around zero magnetic field at low temperatures, has not been observed
The peaks of the reflection high-energy electron diffraction (RHEED) oscillations represent the growth of exact u.c.-control thickness
An atomically smooth surface with clear steps is evidenced in a typical atomic force microscope (AFM) image (1 × 1 μm2) [Fig. 1(b)]
Summary
Vast phenomenological analyses have been fitted to prove the existence of the WL effect[2,11,12], the typical WL effect in magnetoresistance (MR) measurements, i.e., the sharp cusps around zero magnetic field at low temperatures, has not been observed. The conclusion that low-temperature resistivity minima are attributed to QIEs with the combination of e-e interaction and WL effect requires the further direct experimental evidence. The sharp cusps around zero magnetic field in MR measurements is evidenced as the typical WL effect. This leads to the solid conclusion that the low-temperature resistivity minima in single-crystal manganites are the result of QIEs from the combination of e-e interaction and WL effect. The power law fit of phase-coherent length versus temperature further confirms the WL effect of our ultrathin films is within a two-dimensional (2D) localization theory
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