hall effect and conductivity in the single crystals of la sr and la ba manganites
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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) ,

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hall effect and conductivity in the single crystals of la sr and la ba manganites

Hall effect and conductivity in the single crystals of La-Sr and La-Ba manganites

N.G.Bebenin1),R.I.Zainullina1), N.S.Chusheva1), V.V.Ustinov1), Ya.M.Mukovskii2),

1)Institute of Metal Physics, UD RAS, Ekaterinburg, Russia2)Moscow State Steel & Alloys Institute, Moscow, Russia

slide2
1. Introduction

2. Resistivity and Hall effect far below Curie temperature

2.1. The x<xc crystals: La0.85Sr0.15MnO3, La0.85Ba0.15MnO3, and La0.80Ba0.20MnO3

2.2. The x>xc crystals: La0.80Sr0.20MnO3, La0.75Sr0.25MnO3, and La0.72Ba0.28MnO3

3. Temperature-induced metal-semiconductor transition

4. Near TC and in the paramagnetic state

5. Conclusion

slide5

Resistivity of La1-xSrxMnO3 and La1-xBaxMnO3 single crystals(Bebenin et al., PRB 2004, JETP 2000, J. Phys.: Condens. Matter 2005, JMMM 2006)Blue line: inverse minimum metallic conductivity, σmin-1, according to Salamon and Jaime, RMP 2001

slide9

Resistivity and thermopower data suggest that in La0.85Sr0.15MnO3 (TC=232 K) and La0.85Ba0.15MnO3 (TC =214 K) variable range hopping (VRH) dominates below 100 K.

Mott’s model

Shklovskii-Efros model

slide11
Hall mobility in the single crystals with x<xc.xc=0.17 for La1-xSrxMnO3, xc≈0.22 for La1-xBaxMnO3
slide14

Resistivity and Hall mobility in La2/3(Ca,Pb)1/3MnO3 single crystal (TC≈290 K) calculated on the base of data of Chun et al., PRB 1999.

local activation energy a d ln d t 1 for la 0 85 ba 0 15 mno 3 single crystals
Local activation energy εa=d(ln)/d(T-1) for La0.85Ba0.15MnO3 single crystals
slide22

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

conclusion
Conclusion
  • Unlike La1-xSrxMnO3 family, in the x>xc La1-xBaxMnO3 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.
  • The temperature-induced metal-semiconductor transition, if any, occurs well below TC.
  • Near Curie temperature, where CMR effect is observed, all the crystals are in a semiconductor state. Above TC, the crystals are likely to be in the semiconductor state, too. The sign of d/dT is not a sufficient indication of metallic state.
  • 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.
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