Abstract
We present a comparative study of structural and magnetic properties of the as-grown and annealed samples of double perovskite, La2CoMnO6. The single monoclinic (P21/n) phase has been achieved for both the samples. Electron microscopy highlights the change in morphology of the as-grown and annealed samples, with the annealed sample having more grain boundaries and bigger particle sizes. The annealing in presence of oxygen leads to increase in the population of antiphase boundaries, which is supported by the decreases in the remanent and saturation magnetizations. An analysis of magnetization dynamics by means of AC susceptibility shows four different magnetic transitions, with two high temperature ferromagnetic transitions and two cluster glass-like states emerging at low temperatures, which appear almost identical in both the as-grown and annealed samples.
Highlights
LCMO is an insulator and its ferromagnetic (FM) properties are governed by the Goodenough-Kanamori rules, according to which the FM coupling arises due to the 180○ superexchange interaction between the two B-site ions
In a cationically ordered system, LCMO consists of Co2+ and Mn4+ ions, which interact through 180○ superexchange and support FM exchange at high temperature, while the Co3+ and Mn3+ ions lead to vibronic superexchange interactions at comparatively lower temperatures
The x-ray diffractometer (XRD) pattern of LCMO-2 is shown in Fig. 1(a), which is similar to the pattern obtained for LCMO-1.16 A single monoclinic (P21/n) phase was obtained10 for LCMO-2 as well
Summary
Double perovskites (DPs) are very interesting complex oxides with the generic formula A2BB’O6, where A is an alkaline-earth or rare-earth ion and transition metal sites are occupied alternately by different B and B’ cations forming alternating octahedra (BO6 and B’O6) with oxygen. The B-site cations (nominally d-block transition metal ions) offer intriguing possibilities to explore new DPs and study their magnetic and electrical properties. DPs have growing interest in the scientific community because of their exceptional physical properties due to varying and complex compositions which make them promising candidates for novel applications. Among them, La2CoMnO6 (LCMO), has gained a lot of attention owing to its magnetodielectric and multiferroic properties. LCMO is an insulator and its ferromagnetic (FM) properties are governed by the Goodenough-Kanamori rules, according to which the FM coupling arises due to the 180○ superexchange interaction between the two B-site ions. Previous studies on this system suggested that the phase and magnetic properties of LCMO could vary depending upon the synthesis route. It was shown to crystallize into a monoclinic (P21/n or pseudotetragonal) phase or into orthorhombic (Pbnm) and rhombohedral (R3c) phases. It was shown that different synthesis methods gave rise to complicated and multiple crystal structures with variation in cation valences and presence of oxygen deficiencies, which resulted in the inconsistencies of reported magnetic transitions. For LCMO the temperature associated with the paramagnetic (PM) to FM transition is higher if the cationic order in the system is high. For such a highly ordered system, the saturation magnetization is close to the theoretical value, 6 μB/f.u.13 In addition, oxygen vacancies establish mixed valence states of Co and Mn ions, which lead to the appearance of multiple magnetic transitions. The B-site cations (nominally d-block transition metal ions) offer intriguing possibilities to explore new DPs and study their magnetic and electrical properties.. LCMO is an insulator and its ferromagnetic (FM) properties are governed by the Goodenough-Kanamori rules, according to which the FM coupling arises due to the 180○ superexchange interaction between the two B-site ions.. LCMO is an insulator and its ferromagnetic (FM) properties are governed by the Goodenough-Kanamori rules, according to which the FM coupling arises due to the 180○ superexchange interaction between the two B-site ions.9 Previous studies on this system suggested that the phase and magnetic properties of LCMO could vary depending upon the synthesis route.. It was shown that different synthesis methods gave rise to complicated and multiple crystal structures with variation in cation valences and presence of oxygen deficiencies, which resulted in the inconsistencies of reported magnetic transitions.. The results obtained demonstrate the important role of antiphase boundaries on the magnetization of LCMO
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
