MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

Resistivity (10 -3 Ω cm)
10
8
6
4
2
Resistivity (10 -3 Ω cm)
10
9
8
7
6
5
Intrinsic Properties of La 0.67 Ca 0.33 MnO 3
La 0.67 Ca 0.33 MnO 3 Magnetoresistance
La 0.67 Ca 0.33 MnO 3 Film
Magnetization
0 kOe
∆R (0-70 kOe)
240 245 250 255 260 265 270
Temperature(K)
0 kOe
70 kOe
0
0 50 100 150 200 250 300 350 400
Temperature(K)
Figure 4-7 Magnetoresistance of La0.67Ca0.33MnO3 film
(LCM17). Inset, simultaneous magnetization and resistivity at
20Oersted, along with the magnetoresistance [R(H = 0kOe) -
R( H = 70kOe)].
approximately linear with field (Figure 4-8). This effect is small enough for
the analysis to be carried out with R 0 independent of magnetic field.
Since polycrystalline material contains a significant contribution to the
resistivity from grain or domain boundaries, as shown by microwave
measurements [109-111] and higher R 0 values, analysis of the resistivity data
is made only for the well annealed films and crystals. Data up to 70K and
100K for La 0.67 Ca 0.33 MnO 3 and La 0.67 Sr 0.33 MnO 3 , respectively, are well described
with an additional (R 2 ) term proportional to T 2 (Figure 4-8). A linear term in
T did not significantly improve the fit and was not used in later calculations
in order to keep the number of free parameters to a minimum. The field
Magnetization (relative units)
87