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Temperature Dependence of Conductivity and Isotope Effect in the Colossal Magnetoresistance
Author(s) -
Malozovsky Y. M.,
Fan J. D.
Publication year - 1998
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199804)206:2<723::aid-pssb723>3.0.co;2-r
Subject(s) - condensed matter physics , electron , magnetoresistance , curie temperature , ferromagnetism , magnetization , magnetic field , magnetic moment , colossal magnetoresistance , scattering , spin polarization , physics , chemistry , quantum mechanics , optics
The diffusion of electrons in a disordered metal, by means of the perturbation approach, is considered in the presence of a magnetic field. It is shown that the multiple backward scattering of electrons on the randomly oriented or distributed magnetic moments of atoms significantly reduces the diffusion of electrons. Thus, in the diffusive but nearly localized electron system localized magnetic moments appear and a transition into the ferromagnetic phase occurs. The isotope effect in T * C , the Curie temperature, is obtained, as first observed in La 1— x (Ca,Sr) x MnO 3+ y experiments by Zhao and coworkers. Both a relatively weak classical magnetic field (ω c τ 0 < 1, where ω c is the cyclotron frequency, and τ 0 is the elastic collision time) and a molecular field, appearing as result of the spin polarization or spontaneous magnetization in the system, are found to be able to completely suppress the interference effect in the diffusion. It is shown that the giant magnetoresistance is extremely large near the mobility edge. The effect of magnetic field on the magnetic susceptibility is also considered. The application of the results to a layered 2D case is discussed as well.