With increasing the Li doping level in the system is driven from a higher-conductivity regime to a lower-conductivity regime, which is in sharp contrast with the behavior of Na or K doping. Compared to those of K or Na, the ionic radius of Li is much smaller than that of Ca. Therefore, substitution of Ca by Li results in a smaller average A-site radius, narrowing the bandwidth and hence enhancing the band gap and resistivity. The effect of random disorder of and also plays an important role leading to charge localization.
REFERENCES
1.
R.
Von Helmolt
, J.
Wecker
, B.
Holzapfel
, L.
Schultz
, and K.
Samwer
, Phys. Rev. Lett.
71
, 2331
(1993
).2.
S.
Jin
, H. M.
O’Bryan
, T. H.
Tiefel
, M.
McCormack
, and W. W.
Rhodes
, Appl. Phys. Lett.
66
, 382
(1995
).3.
4.
A. J.
Millis
, P. B.
Littlewood
, and B. I.
Shraiman
, Phys. Rev. Lett.
74
, 5144
(1995
).5.
M.
Uehara
, S.
Mori
, C. H.
Chen
, and S.-W.
Cheong
, Nature (London)
399
, 560
(1999
).6.
A.
Moreo
, S.
Yunoki
, and E.
Dagotto
, Science (Washington, DC, U.S.)
283
, 2034
(1999
).7.
M.
Mayr
, A.
Moreo
, J. A.
Verges
, J.
Arispe
, A.
Feiguin
, and E.
Dagotto
, Phys. Rev. Lett.
86
, 135
(2001
).8.
C.
Boudaya
, L.
Laroussi
, E.
Dhahri
, J. C.
Joubert
, and A.
Cheikhrouhou
, J. Phys.: Condens. Matter
10
, 7485
(1998
).9.
N.
Abdelmoula
, A.
Cheikhrouhou
, and L.
Reversat
, J. Phys.: Condens. Matter
13
, 449
(2001
).10.
S.
Roy
, Y. Q.
Guo
, S.
Venkatesh
, and N.
Ali
, J. Phys.: Condens. Matter
13
, 9547
(2001
).11.
S.
Bhattacharya
, A.
Banerjee
, S.
Pal
, P.
Chatterjee
, R. K.
Mukherjee
, and B. K.
Chaudhuri
, J. Phys.: Condens. Matter
14
, 10221
(2002
).12.
S.
Bhattacharya
, A.
Banerjee
, S.
Pal
, R. K.
Mukherjee
, and B. K.
Chaudhuri
, J. Appl. Phys.
93
, 356
(2003
).13.
S. L.
Ye
, W. H.
Song
, J. M.
Dai
, K. Y.
Wang
, J. J.
Du
, and Y. P.
Sun
, J. Appl. Phys.
89
, 7419
(2001
).14.
N. F. Mott and E. A. Davis, Electronics Process in Non Crystalline Materials (Clarendon, Oxford, 1971).
15.
S.
Pal
, A.
Banerjee
, E.
Rozenberg
, and B. K.
Chaudhuri
, J. Appl. Phys.
89
, 4955
(2001
);M.
Viret
, L.
Ranno
, and J. M. D.
Coey
, Phys. Rev. B
55
, 8067
(1997
).
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