First-principles KKR-CPA calculation of the magnetic and transport properties of La₁-xXxMnO₃ (X = Ca, Sr).
Electrical transport properties of (La(1-x)X(x))MnO(3) (X = Ca, Sr), which exhibits the so-called colossal magnetoresistance (CMR) effect, are investigated in the framework of linear response theory combined with first-principles calculation. The calculation is performed by applying the coherent potential approximation and Kubo-Greenwood formula to the KKR Green's function method. In order to reveal the mechanism that underlies the CMR effects, the dc conductivities of the system in A (layered)-, C (stripe)-, and G (111)-type antiferromagnetic states as well as the local moment disordered state are calculated as a function of x. It is found that the conductivity of the system strongly depends on the magnetic structure and is highly anisotropic in the cases of A- and C-type antiferromagnetic structures. Also, it is concluded that a drastic change in the conductivity is expected when the system undergoes a magnetic transition, and that this might be closely related to the observed CMR effect. It is pointed out that, for such a drastic change in the conductivity to occur associated with the magnetic transition, the half-metallic nature of the Mn local electronic structure must be essential.
Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan. ogura@phys.sci.osaka-u.ac.jp
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