1. Hall effect and conductivity in the single crystals of La-Sr and La-Ba manganites N.G.Bebenin 1), R.I.Zainullina 1), N.S.Chusheva 1), V.V.Ustinov 1), Ya.M.Mukovskii 2), 1) Institute of Metal Physics, UD RAS, Ekaterinburg, Russia 2) Moscow State Steel & Alloys Institute, Moscow, Russia

2. 1. Introduction 2. Resistivity and Hall effect far below Curie temperature 2.1. The x<x c crystals: La 0.85 Sr 0.15 MnO 3, La 0.85 Ba 0.15 MnO 3, and La 0.80 Ba 0.20 MnO 3 2.2. The x>x c crystals: La 0.80 Sr 0.20 MnO 3, La 0.75 Sr 0.25 MnO 3, and La 0.72 Ba 0.28 MnO 3 3. Temperature-induced metal-semiconductor transition 4. Near T C and in the paramagnetic state 5. Conclusion

3. Resistivity of La 1-x Sr x MnO 3 single crystals (Urushibara et al., PRB 1995)

4. Resistivity of La 1-x Sr x MnO 3 single crystals (Anane et al., J. Phys.:Condens. Matter 1995)

5. Resistivity of La 1-x Sr x MnO 3 and La 1-x Ba x MnO 3 single crystals (Bebenin et al., PRB 2004, JETP 2000, J. Phys.: Condens. Matter 2005, JMMM 2006) Blue line: inverse minimum metallic conductivity, σ min -1, according to Salamon and Jaime, RMP 2001

6. Magnetoresistance Δ  /  =[  (H)-  (0)]/  (0) for La-Sr single crystals (H=10 kOe)

7. Magnetoresistance Δ  /  for La-Ba single crystals (H=10 kOe)

8. Electronic specific heat coefficient γ for La 1-x Sr x MnO 3 (T.Okuda et al. PRL 1998)

9. Resistivity and thermopower data suggest that in La 0.85 Sr 0.15 MnO 3 (T C =232 K) and La 0.85 Ba 0.15 MnO 3 (T C =214 K) variable range hopping (VRH) dominates below 100 K. Mott’s model Shklovskii-Efros model

10. Hall resistivity vs magnetic field for La 0.72 Ba 0.28 MnO 3 (T C =310 K)  Hall =R o H+R s M

11. Hall mobility in the single crystals with x<x c. x c =0.17 for La 1-x Sr x MnO 3, x c ≈0.22 for La 1-x Ba x MnO 3

12. Low temperature (T x c crystals obeys T 2 -law

13. Hall mobility in the x>x c La-Sr and La-Ba single crystals

14. Resistivity and Hall mobility in La 2/3 (Ca,Pb) 1/3 MnO 3 single crystal (T C ≈290 K) calculated on the base of data of Chun et al., PRB 1999.

15. Anomalous Hall coefficient in La 1-x Sr x MnO 3 single crystals (Bebenin et al., PRB 2004)

16. Hall effect in La 2/3 (Ca,Pb) 1/3 MnO 3 (Chun et al., PRB 1999)

17. Resistivity of La-Sr single crystals near Curie temperature

18. Resistivity of La-Ba crystals near Curie temperature (H=10 kOe)  =  o exp[(E o -E 1 m 2 )/k B T)

19. Magnetoresistance of La 0.72 Ba 0.28 MnO 3 (T C =310 K) as a function of m 2

20. Critical behavior of E 1 (T) in La 0.72 Ba 0.28 MnO 3

21. Local activation energy ε a =d(ln  )/d(T -1 ) for La 0.85 Ba 0.15 MnO 3 single crystals

22. Temperature dependence of the metallic phase volume in some lightly doped manganites derived from optical measurements (Mostovshchikova et al., PRB 2004)

23. Local activation energy ε a =dln  /d(T -1 ) in La 1-x Sr x MnO 3

24. Conclusion 1.Unlike La 1-x Sr x MnO 3 family, in the x>x c La 1-x Ba x MnO 3 single crystals electrons – not holes - are majority carriers. Thus the band structure depends on not only doping level but also on type of divalent ion. 2. The temperature-induced metal-semiconductor transition, if any, occurs well below T C. 3.Near Curie temperature, where CMR effect is observed, all the crystals are in a semiconductor state. Above T C, the crystals are likely to be in the semiconductor state, too. The sign of d  /dT is not a sufficient indication of metallic state. 4.The conductivity mechanisms in the manganites with different doping is different. A general formal reason for the CMR effect in the La-Sr and La-Ba single crystals consists in the change of activation energy under application of a magnetic field.