Charge transport in manganites: Hopping conduction, the anomalous Hall effect, and universal scaling

Abstract

The low-temperature Hall resistivity ρxy of La 2/3 A 1/3 MnO3 single crystals (where A stands for Ca, Pb and Ca, or Sr) can be separated into Ordinary and Anomalous contributions, giving rise to Ordinary and Anomalous Hall effects, respectively. However, no such decomposition is possible near the Curie temperature which, in these systems, is close to metal-to-insulator transition. Rather, for all of these compounds and to a good approximation, the ρxy data at various temperatures and magnetic fields collapse (up to an overall scale), on to a single function of the reduced magnetization m ≡ M/Msat, the extremum of this function lying at m ≈ 0.4. A new mechanism for the Anomalous Hall Effect in the inelastic hopping regime, which reproduces these scaling curves, is identified. This mechanism, which is an extension of Holstein's model for the Ordinary Hall effect in the hopping regime, arises from the combined effects of the double-exchange-induced quantal phase in triads of Mn ions and spin-orbit interactions. We identify processes that lead to the Anomalous Hall Effect for localized carriers and, along the way, analyze issues of quantum interference in the presence of phonon-assisted hopping. Our results suggest that, near the ferromagnet-to-paramagnet transition, it is appropriate to describe transport in manganites in terms of carrier hopping between states that are localized due to combined effect of magnetic and non-magnetic disorder. We attribute the qualitative variations in resistivity characteristics across manganite compounds to the differing strengths of their carrier self-trapping, and conclude that both disorder-induced localization and self-trapping effects are important for transport.

Magnetic phase diagram and structural separation of La0.7(Ca1−ySry)0.3MnO3 thin films

“…The similar variation of the MR͑H͒ behavior at T Ն T C have already been observed in these lanthanides and explained by a transition from the insulating to metal-like state with the increasing of Sr concentration. [24][25][26][27] V. DISCUSSION Figure 7 exhibits the magnetic phase diagram for La 0.7 ͑Ca 1−y Sr y ͒ 0.3 MnO 3 films deposited on the LAO substrate. The triangular symbols display T P , the MI transition temperature.…”

Scaling of the Anomalous Hall Effect inSr1−xCaxRMathieu1, Asamitsu2, Yamada3 et al. 2004Phys. Rev. Lett.Self Cite147161121View full textAdd to dashboardCite

“…Therefore the magnitude of the AHE depends on the concentration and scattering strength of impurities, thermal spinagitation, etc. In contrast to these extrinsic mechanisms, several works [4,5,6,7,8] regard AHE of the intrinsic origin. Namely the phase of the Bloch wave-function in the momentum space determines the Hall conductivity σ xy , which is largely determined by the band crossing points acting as "magnetic monopoles" [9].…”

Polaron framework to account for transport properties in metallic epitaxial manganite films

“…In order to demonstrate the validity of the polaron metal transport model proposed in this paper and to assert its general relevance, the model is successfully applied to the metallic phase of single crystals of La 0.67 Ca 0.33 MnO 3 (LCMO), La 0.67 (Ca 1/3 Pb 2/3 ) 0.33 MnO 3 (LCPMO), and LSMO, taking the data from the literature [57], and the showing the results in Fig. 6.…”