MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

Critical Transport and Magnetization of La 0.67 Ca 0.33 MnO 3
values for β reported here are more uncertain than those reported for other
materials.
M 0 (µ B /Mn)
2.5
2.0
1.5
1.0
0.5
ln(M)
1.0
0.5
0.0
-0.5
M ∝ (Tc-T) β
β = 0.30
-1.0
-2 -1 0 1 2 3 4 5
ln(262.2-T)
0.0
190 200 210 220 230 240 250 260 270
Temperature (K)
Figure 7-3. Saturation Magnetization, M 0 as a function of
temperature for La 0.67 Ca 0.33 MnO 3 crystal. At each temperature,
the value shown is M extrapolated to H = 0 as given by the
intercept in Figure 7-1.Solid line is fit to M 0 (T) ∝ (1 - T/T C ) β
with β = 0.30.
Typical experimental values for the critical exponent β in Fe, Ni and YIG
[92] are 0.37 ± 0.02, which are near the theoretical values (Ising β = 0.33,
Heisenberg β = 0.36). The related metallic ferromagnets SrRuO 3 (Appendix A)
and La 0.5 Sr 0.5 CoO 3 [92] have β ≈ 0.36 and β = 0.361 respectively. Previous
magnetic data [166, 167] on La 0.67 Ca 0.33 MnO 3 have been fit with such values of
β, suggesting that the critical region has been reached. For example, muon-
133