Colossal-magnetoresistance materials: manganites and conventional ferromagnetic semiconductors

Experimental data and their theoretical interpretation are presented for the colossal magnetoresistance (CMR) materials to which conventional ferromagnetic semiconductors and manganites belong. The similarity between the transport and magnetotransport properties of the ferromagnetic semiconductors and manganites is stressed. Different theoretical points of view on the physics of the phenomenon are presented, including the magnetoimpurity theory and “magnetization+Jahn–Teller phonon” theory. Of the manganites, the La-based underdoped, normally doped, and overdoped manganites are discussed in detail, including the dilemma “canted antiferromagnetic ordering or phase separation” and different models of charge ordering. Radical difference between the Pr-based and La-based manganites is explained. Layered manganites are considered, too.