Is the ferromagnetic insulating phase different from the ferromagnetic metallic phase at the microscopic level or they are same at microscopic level?
If you go to p. 137 of the book
Colossal manetoresistive manganites, ed. Tapan Chatterji,Kluwer Academic Publishers, Dordrecht (2004)
you will see the phase diagram of La1-xCaxMnO3 which is a canonical manganite system. This is the chapter 4 of the book. This phase diagram shows clearly around x = 1/8 three phases as a function of temperature. At room temperature you have orbitally ordered O' phase which transforms into orbitally disordered pseudo-cubic O phase phase at higher temperatures. At low temperature below about T_N = 150 K the material has a ferromagnetic insulting (FI) phase which is different from the ferromagnetic metallic (FMM) phase for x > 0.2. This ferromagnetic insulating phase transforms into a charge and orbital ordered insulating COI phase. The ferromagnetic insulating FI phase ,in contrast to the FMM phase, does not show CMR effect. If you read the chapter 3 then you will see that the spin dynamics in the FI is quite different from that of the FMM phase described in chapters 7 and 8. In chapters 1, 2 and 4 you will find the description of the different properties of FI and FMM phase. So read all these first. If you do not understand anything then do not hesitate to come back to me with further questions.
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