MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

106 Chapter 5
χ mol (µ B /mol/T)
0.40
0.36
0.32
0.28
0.24
0.20
High Field Susceptibility of Gd 0.67 Ca 0.33 MnO 3
Magnetization (µ B /mole)
0 10 20 30 40 50 60 70 80
Temperature (K)
3
2
1
0
5K
0 10 20 30 40 50 60 70
Magnetic Field (kOe)
Figure 5-3 Low temperature and high-field magnetic
susceptibility, χ = (M(60 kOe)-M(40 kOe))/20kOe, of
Gd 0.67 Ca 0.33 MnO 3 crystal. Inset, hysteresis loop at 5 K.
The hysteresis loop at 5 K (Figure 5-3) shows an additional high field
paramagnetic response not expected for a mean field ferrimagnet. It is not
uncommon, however, to observe such a field-induced increase of the
magnetization in canted ferromagnetic or ferrimagnetic systems [140, 141],
and is used as evidence of the ferrimagnetic sublattices canting away from
antiparallel [101]. The magnetic field affects the canting angle, which results
in the magnetization increasing nearly linearly with field even at T = 0 K
[140]. If this large susceptibility were due to a second phase with free
paramagnetic spins, then this phase would have to contain at least half of the
available spins and have a 1/T temperature dependence for all T. This is not