MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

Magnetization (emu/g)
80
60
40
20
Intrinsic Properties of La 0.67 Ca 0.33 MnO 3
Magnetization (emu/g)
100
50
0
-50
La 0.67 Sr 0.33 MnO 3 Polycrystalline Pellet
0
0 50 100 150 200 250 300 350 400
Temperature (K)
is the largest. The term “CMR” is used here when the magnetoresistance
ratio ∆R/R(H) is greater than 10 (or 1000%).
b
5K
-100
-75 -50 -25 0 25 50 75
Magnetic Field (kOersted)
10 kOersted
4.1 Magnetism
The polycrystalline samples have relatively square hysteresis loops (Figure
4-1), with forced magnetization at 70kOe of only a few percent. The saturation
magnetizations are close to that expected for high spin manganese in
octahedral coordination: for spin only (orbital contribution quenched)
moment µ = gsµ b , g=2 and then µ= 2µ b [0.67 x 2 (from Mn 3+ ) + 0.33 x 3/2 (from
Mn 4+ )] = 3.67µ b . The measured ferromagnetic and Curie temperatures are the
same within experimental error of a few degrees. The physical properties of
the polycrystalline materials summarized in Table 4-1 Physical Properties of
Polycrystalline Pellets are consistent with previous results [1-4, 29, 106, 107].
10
8
6
4
2
a
100 Oe
0
370 372 374 376378 380
Temperature (K)
Figure 4-1 Magnetization of La 0.67 Sr 0.33 MnO 3 polycrystalline
pellet at 10kOe. Inset a, magnetization at 100Oe used to
determine T C = 375K. Inset b, full hysteresis loop at 5 K.
81