Hall effect ofLa2/3(Ca,Pb)

Abstract

The Hall resistivity ρ xy of a La 2/3 (Ca,Pb) 1/3 MnO 3 single crystal has been measured as a function of temperature and field. The overall behavior is similar to that observed previously in thin-films. At 5 K, ρ xy is positive and linear in field, indicating that the anomalous contribution R S is negligible.However, the effective carrier density in a free electron model is n ef f = 2.4 holes/Mn, even larger than the 0.85-1.9 holes/Mn reported for thin-films and far larger than the 0.33 holes/Mn expected from the doping level. As temperature increases, a strong, negative contribution to ρ xy appears, that we ascribe to R S . Using detailed magnetization data, we separate the ordinary (∝ B) and anomalous (∝ M ) contributions. Below T C , |R S | ∝ ρ xx , indicating that magnetic skew scattering is the dominant mechanism in the metallic ferromagnetic regime. At and above the resistivity-peak temperature, we find that ρ xy /ρ xx M is a constant, independent of temperature and field. This implies that the anomalous Hall coefficient is proportional to the magnetoresistance. A different explanation based on two fluid model is also presented.Typeset using REVT E X 1

Ambipolar ferromagnetism by electrostatic doping of a manganite

“…The AHE starts to dominate above ~100 K, increases sharply around the Curie temperature ( T C ), peaking at a temperature roughly 30 K above T C , and decreases slowly at higher temperatures 29 . Figure 2b, c shows ρ xy of LMO at various temperatures in the electron-doped and hole-doped regimes, exhibiting an AHE which is in good agreement with studies on La 1− x A x MnO 3 (A = Ba, Ca, Pb, Ce, and Sr) single crystals 23,30,31 . Typically, the AHE in hole-doped manganites, such as La 1− x Sr x MnO 3 and La 1− x Ca x MnO 3 , is prominent 31 at temperatures close to the Curie temperature, T C , namely in the higher temperature region of the metallic phase, where d ρ xx /d T is positive and the lower temperature region of the insulating phase, where d ρ xx /d T is negative.…”

Anomalous Hall effect in paramagnetic two-dimensional systems

“…When spin orbit is included the k=0 band wavefunctions are eigenstates of the total angular momentum operator J, splitting into a fourfold degenerate j=3/2 level (containing the heavy holes and the light holes) and a twofold degenerate j=1/2 level (the split off band). Away from k=0, there is a correction proportional to (Ĵ · k) 2 , which partially lifts the degeneracy of the bands. This term provides a k-dependent quantization direction for the angular momentum, so that as the wavevector is displaced the angular momentum is rotated and it is possible to obtain a nonzero Berry curvature.…”

Magnetocrystalline anisotropy in a single crystal ofCeNiGe2

“…From this γ value, the Kondo temperature is estimated to be about T K = 40 K, 12 close to that (T K = 50 K) obtained from the paramagnetic Curie temperature θ P . Even in the magnetically ordered Recently, a very large anomalous Hall effect was found in colossal magnetoresistance manganites 13 and was explained by Berry phase theory based on carrier hopping in a nontrivial spin background. The specific heat C(T) was measured at various magnetic fields, zero, 2, 4, and 6 T for H⊥b and H//b.…”