MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

90 Chapter 4
magnetoresistance observed in the temperature range used to fit the
conductivity data is absorbed primarily in the T 4.5 term. This universality
with respect to growth, composition, and magnetic field leads us to conclude
that the T 2 term in the resistivity represents intrinsic behavior of
La 0.67 AE 0.33 MnO 3 compounds.
Resistivity (10 -3 Ω cm)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
La 0.67 (Sr/Ca) 0.33 MnO 3 Low Temperature Resistivity
LSM Film
LCM Film
0.1
0.0 0.1 0.2 0.3
(T/T )
C
0.4 0.5
2
Figure 4-8 Low temperature resistivity (in zero field) of
La 0.67 (Sr/Ca) 0.33 MnO 3 films (LSM1 and LCM10). Solid lines are
the fit to R 0 + R 2 T 2 + R 4.5 T 4.5 up to 250K and 200K for LSM and
LCM respectively. The dashed lines show the constant and T 2
terms of the best fit.
Significant T 2 dependencies in resistivity [117] are often observed in
metallic ferromagnets such as Fe, Co, and Ni where the coefficient [118] is 10 -11
Ωcm/K 2 . The magnitude of R 2 is expected [84, 119] to scale with 1/M 0 , which
explains the larger 5 x 10 -8 Ωcm/K 2 value for R 2 found in the weak itinerant