Role of Annealing Atmosphere on Structure, Dielectric and Magnetic Properties of La₂CoMnO₆ and La₂MgMnO₆

Abstract

Polycrystalline samples of La 2 MMnO 6 (M = Co and Mg) were prepared by a combined gel-combustion and high temperature reaction method. The samples were annealed in different oxygen partial pressure (p O2 ) and characterized by powder XRD, SQUID magnetometry, ac impedance spectroscopy, and electron paramagnetic resonance techniques. Monoclinic (P2 1 /n) and rhombohedral (R3) lattices were observed for La 2 CoMnO 6 and La 2 MgMnO 6 , respectively. On annealing in inert atmosphere, La 2 MgMnO 6 partially converted to monoclinic La 2 CoMnO 6 type structure, whereas no structural change was observed in La 2 CoMnO 6 .

Effects of different annealing atmospheres on magnetic properties in La2CoMnO6 single crystals

“…Small portion of these clusters often leads to a spin-glass state and metamagnetic transition [11,22,25,26]. The previous reports on polycrystalline samples demonstrate that the resulting magnetic properties vary with synthesizing processes and annealing conditions [20,21,27]. In polycrystalline LCMO prepared by the Pechini method, the different post-annealing procedure results in the considerable modification in magnetic properties such as the shift of ferromagnetic transition temperature and alteration of magnetic hysteresis curve [20,21,27].…”

“…The previous reports on polycrystalline samples demonstrate that the resulting magnetic properties vary with synthesizing processes and annealing conditions [20,21,27]. In polycrystalline LCMO prepared by the Pechini method, the different post-annealing procedure results in the considerable modification in magnetic properties such as the shift of ferromagnetic transition temperature and alteration of magnetic hysteresis curve [20,21,27]. The polycrystalline Eu 2 CoMnO 6 sintered at high temperature reveals the spin glass behavior as well as metamagnetic transitions [8].…”

Temperature-dependent structural and magnetic properties of R2MMnO6 double perovskites (R = Dy, Gd; M = Ni, Co)

“…Neighbor pairs of Co and Mn atoms turn into Co 2+ and Mn 4+ in the case of structural order at B-sublattice, whereas the fraction of Co 3+ / Mn 3+ (high spin) in R 2 CoMnO 6 increases as the disorder of Co and Mn ions is enhanced [58]. Factors influencing the extent of cation order in double perovskites are charge differences between the B-cations, their differences in ionic radii, the polarization of certain cations and synthetic conditions [59].…”

Electrical transport properties and enhanced magnetoresistance effect in double perovskite La2–xCaxCoMnO6 (0 ≤ x ≤ 0.5)

“…Double perovskite La 2 CoMnO 6 , one type of A 2 BB'O 6 , has been extensively studied due to its rich physical properties . The strong ferromagnetic (FM) super‐exchange interactions between Co and Mn ions lead to the high FM behavior of this material with a Curie temperature ( T C ) as high as 220 K .…”