Competing magnetic interactions and emergent phase diagrams in double perovskite Y2NixCo1−xMnO6

Abstract We present a comparative study of double perovskites Y2NixCo1−xMnO6 for x = 1, 0.5, and 0. The polycrystalline samples of Y2NixCo1−xMnO6 with space group P21/n were synthesized via sol-gel technique. X-ray photoelectron spectroscopy (XPS) confirms the presence of majority Ni2+/Mn4+ in Y2NiMnO6 (YNMO) and a mixed valence state Ni2+/3+/Co2+/3+/Mn4+/3+ in co-doped Y2Ni0.5Co0.5MnO6 (YNCMO). The temperature dependent magnetization results suggest homogeneous substitution of Ni ions with Co ions with minimal contribution of 3 + cationic magnetic interactions in YNCMO. The superexchange ferromagnetic (FM) interaction has a major contribution to the magnetism of YNMO. The strength of antiferromagnetic (AFM) coupling resulting from the antiphase boundaries in Y2NixCo1−xMnO6 increases with the increase in the Co concentration. The AC susceptibility (AC-χ) study further validates the presence of higher density of antiphase boundaries, which is reflected by the dynamics of domain walls in YNCMO. The isothermal magnetic entropy change (ΔSM) as functions of temperature and magnetic field is exploited to assess the stabilization of different magnetic phases. The findings of ΔSM (T,µ0H) lead to the proposed new magnetic phase diagrams for Y2NixCo1−xMnO6 for x = 1 and 0.5, in comparison with the previously established phase diagram of Y2CoMnO6.