MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

Electronic and Magnetic Measurements 67
in polycrystalline SrRuO 3 , the irreversibility will be evident in many
measurements. The coercivity depends on the microstructure of the sample,
and therefore depends on the processing. SrRuO 3 single crystal for instance
(Appendix A) has a coercive field 100 times smaller than polycrystalline
SrRuO 3 .
Magnetization (µ B )
0.8
0.6
0.4
0.2
0.0
SrRuO 3 initial magnetization
Inflection Point
0 1000 2000 3000 4000 5000
Magnetic Field (Gauss)
Figure 3-13 Initial magnetization of SrRuO 3 pellet at 5 K, after
cooling in zero field. The magnetization follows a “S” shaped
curve providing an inflection point.
In the irreversible regime, a ferromagnet will have magnetic properties
similar to that of a spin glass [98]. For example, it is common to characterize
spin glasses [99] (or disordered superconductors) by comparing the field-cooled
(sample cooled below T C in the measuring field) and zero-field-cooled
(sample cooled in zero field and then the field applied before measuring upon
warming) magnetization in a small field. For a spin-glass or disordered
superconductor, these two curves are different. In such small fields, a