Phase Separation in Jahn-Teller Systems with Localized and Itinerant Electrons

The phase diagram for doped manganites and related compounds is analyzed in terms of the Kondo-lattice model taking into account an interplay between electrons localized due to lattice distortions and those in the band states. It is shown that the number of itinerant charge carriers can be significantly lower than that implied by the doping level. The competition between the homogeneous (ferromagnetic or antiferromagnetic) and phase-separated states is discussed and a strong tendency to the phase separation was revealed for a wide doping range.

Figure 1

$n_l$ (solid line) and $n_b$ (dashed line) vs doping level $x$; ${ϵ}_{\mathrm{JT}}/w_0=0.05$; $j=zJ/w_0=0.005$.

Figure 2

The energy of the system in FM (solid line) and AF (dashed line) states vs doping level $x$; ${ϵ}_{\mathrm{JT}}/w_0=0.05$; $j=zJ/w_0=0.005$.

Figure 3

The energy of the system vs doping level $x$. The solid line corresponds to the homogeneous (AF at $x<x^{*}$ or FM at $x>x^{*}$) state. The dashed lines correspond to energies of the phase-separated state calculated at $u/w_0=2,3/2,1,1/4,0$ from up to down. Other parameters are ${ϵ}_{\mathrm{JT}}/w_0=0.05$ and $j=zJ/w_0=0.005$. The regions of stability of AF, FM, and AF-FM phase-separated states are shown at $u/w_0=3/2$.