Colossal magnetoresistance (CMR) is a property of some materials, mostly manganese-based perovskite oxides, that enables them to dramatically change their electrical resistance in the presence of a magnetic field.
[3][4] Initially discovered in mixed-valence perovskite manganites in the 1950s by G. H. Jonker and J. H. van Santen,[5][6] a first theoretical description in terms of the double-exchange mechanism was given early on.
One prominent model is the so-called half-metallic ferromagnetic model, which is based on spin-polarized (SP) band structure calculations using the local spin-density approximation (LSDA) of the density functional theory (DFT) where separate calculations are carried out for spin-up and spin-down electrons.
In SP calculations of covalent ferromagnets using DFT-LSDA functionals, the exchange-correlation integral takes the place of the Stoner parameter.
[14] A significant advantage of the half-metallic model is that it does not rely on the presence of mixed valency as does the double exchange mechanism and it can therefore explain the observation of CMR in stoichiometric phases like the pyrochlore Tl2Mn2O7.