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In recent years, the B-site ordered double perovskite La₂BB’O₆ (B= Co, Ni and B’= Mn)   received much attention because of the magnetodielectric effect exhibited by them. The debate about the origin of this effect is still unsettled [1-2]. The magnetodielectric effect could also arise from the magnetostriction effect which refers to  the dimensional changes of a material under the action of an external magnetic field. However, no studies of magnetostriction available earlier, The first report of magnetostriction in La₂CoMnO₆ appeared only very recently[3]. Here, we try to understand correlation between the magnetostriction and magnetodielectric effects in La₂CoMnO₆. Polycrystalline insulating ferromagnetic double perovskite La₂CoMnO₆ possessing monoclinic structure and a high Curie temperature (T_C = 222 K) was rapidly synthesized (~30 min) by  the novel method of microwave synthesis, which involves irradiating stoichiometric mixture of oxides with microwaves of frequency 2.45 GHz. The sample exhibits negative magnetostriction (λ_par), i.e., contraction of length along the magnetic field direction in the ferromagnetic state. At 10 K, λ_par does not show saturation up to a magnetic field of 50 kOe where it reaches 610 x 10^-6 which is one of the highest values of magnetostriction found so far among perovskite oxides with 3d ions. The magnetodielecric effect of microwave synthesized shows the maximum value of 15% around 125 K for H = 5 T.  We compare the dc magnetoresistance, ac magnetoresistance, magnetic loss, and magnetostriction to address the origin of magnetodielectric effect in this compound.

References

[1] N.Ragodo et al.,  Adv. Mat. 17, 2225 (2005); P. Padhan et al., Appl. Phys. Lett.92, 022909 (2009).

[2] M. P. Singh et al., Appl. Phys. Lett. 91,042504 (2007); J. Krishnamurthy et al.,  J. Appl. Phys. 111, 024102 (2012); K. Manna et al., J. Appl. Phys. 119, 043906 (2016).

[3]  M. Manikandan, A. Ghosh and R. Mahendiran, Appl. Phys. Lett. 122, 022403 (2023).