The ordered oxygen deficient `112’ perovskites, LnBaCo2O5.50+𝛿 (Ln = lanthanide or Y), exhibit a very flexible structure which can either uptake (𝛿 > 0) or release oxygen (𝛿 < 0) depending on the experimental conditions of synthesis and on the size of the lanthanide. These compounds exhibit remarkably complex magnetic transitions, metal–insulator transition and exceptionally high magnetoresistance. We show herein that their physics is mainly dominated by three different ferromagnetic states, depending on the cobalt valency: FM1 for 𝛿 = 0 (Co3+), FM2 for 𝛿 < 0 (Co2+/Co3+) and FM3 for 𝛿 > 0 (Co3+/Co4+). The competition between ferromagnetism and antiferromagnetism in these phases and the various transitions are discussed taking into consideration the spin state of cobalt, the issue of phase separation and the effect of cobalt coordination and disproportionation.
Volume 44, 2021
Continuous Article Publishing mode
Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020
Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
Physical Sciences 2020
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