Crystal Structure and Magnetic Properties in B-Site-Disordered La1.75Ca0.25MnMO6 (with M = Ti and Fe) Double Perovskites


Double perovskite La1.75Ca0.25MnMO6 (with M = Ti and Fe) systems were elaborated employing a solid-state reaction method. The refinement of X-ray diffraction patterns shows that La1.75Ca0.25MnFeO6 (LCMFO) and La1.75Ca0.25MnTiO6 (LCMTO) compounds crystallize in an orthorhombic structure with the Pbnm space group. The electron density plots indicated the covalent nature between Mn/Ti/Fe and oxygen ions. The results of the temperature dependence of the magnetization show that these samples present a paramagnetic-antiferromagnetic transition at 230 K and 223 K for LCMFO and LCMTO, respectively. The non-null magnetization and magnetic hysteresis loop at room temperature can indicate the formation of weak ferromagnetism in the paramagnetic (PM) region in both compounds. Moreover, our magnetic results show a complex magnetic response in these materials below T-N, which can be attributed to the formation of various types of magnetic exchange interactions within the system such as antiferromagnetic (AFM), (ferromagnetic) FM, and ferrimagnetic (FiM) couplings. Consequently, exchange coupling between the FM and/or FiM moments and AFM antiphase boundaries is responsible for the observation of exchange bias in the materials. Considering practical applications of perovskites, the present observation of the exchange bias effect and room temperature ferromagnetism in these materials may have great technological importance.






Selmi, R; Cherif, W; Sarabando, AR; Ferreira, NM; Ktari, L

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This paper within the framework of collaboration is supported by the Tunisian Ministry of Higher Education and Scientific Research and the Portuguese Ministry of Science, Technology and Higher Education. The authors acknowledge the i3N (UID/CTM/50025/2020) and CICECO-Aveiro Institute of Materials (UID/CTM/50011/2020), financed by FCT/MEC and FEDER under the PT2020 Partnership Agreement. This work is also funded by national funds (OE), through FCT - Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19.

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