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Crystal Structure Phase Transitions in the PerovskitesA(Cul,Mn,)MnaOle(A = Na+, Cae+, Y8+, La8+) X-Ray diffraction and neutronographical studies on the crystal structure of the perovskitelike compounds A(Cu1 -zMnz)3Mn40,z have been undertaken. It has been shown t h a t the samples with 60% of Mn3+ in the octahedral sites have a cubic unit cell, while the samples with higher Mn3+ composition may have a monoclinic or rhombohedra1 unit cell. The temperature increase raises the symmetry to the cubic one. The concentretion ranges with different symmetry type have been determine&. The lowering of the symmctry of thr u n i t cell is due to the cooperative Jahn-Teller effect.

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