We report magnetic, dielectric, magnetodielectric, and magnetocaloric responses of La2CoMnO6 (LCMO) and Sr doped La2−xSrxCoMnO6 (x = 0.5 and 1.0) induced by antisite disorder. The antisite disorder is enhanced with Sr-doping at La-sites. Co ions have mixed valence states on Sr-doping, with Co3+ and Co2+. Mn is present in mixed valence of Mn4+ and Mn3+ states with Sr doping. The dielectric constant of Sr doped LCMO was found to increase, whereas the magnetodielectric coupling was found suppressed due to the increase of antisite disorder. The magnetic field-dependent magnetodielectric effect clearly shows M2 behavior for all the samples in the field range of 0 to ±6 T in their respective ferroic phases. All the samples show spin glass like ordering in the ground state. We also report the magnetic entropy change in magnetoelectric material La2−xSrxCoMnO6 (x = 0, 1.0) samples. The change in magnetic entropy ΔSm originates mainly from the combined effect of the ferromagnetic/antiferromagnetic interaction and the magnetodielectric effect in La2−xSrxCoMnO6 (x = 0, 1.0). The observed value of the magnetocaloric effect (1.2 J/kg K) for x = 1.0 is likely to originate from the antisite disordered phases near Curie temperature.

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The parent compound SmFeAsO shows structural phase transition from tetragonal to orthorhombic at the temperature T D = 144 K. In the compound SmFe 1-x Co x AsO, with increasing x the structural transition temperature T D and SDW T N decreases and reaches 0 K at the critical concentration x c . The X-ray diffraction technique has been used here to study the structural phase transition temperature. It is observed that the (400) peak of the parent compound SmFeAsO splits into two peaks (400) and (040)

compound is well Known to show the frustration of the spin structure. At 12 K, distorts to break symmetry of the degenerated frustrated spin states by the spin-Peierls-like phase transition, accompanying with the antiferromagnetic ordering. On the other hand, undergoes a Jahn–Teller phase transition at a temperature of 310 K, differing from the low temperature ferrimagnetic transition temperature of about 60 K. It is also reported that shows another magnetic phase transition at about 30 K. These two phase transitions accompanying with the lattice change can be understood by the magneto-elastic interactions. Two interactions, the Jahn–Teller interaction and the spin-Peierls-like interaction are co-exist in system. In this report the compounds with x = 0.8, 0.6 and 1 are investigated by the X-ray diffraction measurements. From these measurements the crystal structures are determined. The full width at half maximum and integrated intensity give the fruitful information for magnetic elastic interactions.