Experimental and DFT analysis of antisite disorder and Griffiths phase in Dy2CoMnO6: structural, electronic, and magnetic insights

Abstract

The intricate interaction of emergent degrees of freedom, ground state degeneracy, and competing magnetic interactions in oxide-based double perovskite frustrated magnets can give rise to exotic excitations and correlated quantum phenomena with promising technological applications. This study investigates the structural, magnetic, and electronic properties of Dy₂CoMnO₆ synthesized via solid-state reaction. Rietveld refinement of XRD data confirms a monoclinic P2₁/n structure, with Raman spectra revealing BO₆ polyhedral dynamics. XPS analysis indicates mixed valence states of Co and Mn. Magnetic measurements show ferromagnetic ordering below T_c = 87 K due to Co²⁺–Mn⁴⁺ superexchange, along with a Griffiths phase above T_c (T_G = 91 K) and canted antiferromagnetic correlations at low temperature. A coercivity of 6.8 kOe at 10 K further supports FM behavior. Density functional theory (DFT) calculations validate the stability of Dy₂CoMnO₆ in the ferromagnetic phase, showing that the ferromagnetic state is energetically more favorable than the antiferromagnetic state. The direct band gap of Dy₂CoMnO₆ was found to be approximately 1.47 eV, while the indirect band gap was around 1.04 eV. Electronic band structure and density of states calculations predict band gaps of 1.60 eV and 3.20 eV for the minority and majority spin orientations, respectively, confirming the semiconductor nature of Dy₂CoMnO₆. These calculated values closely match the experimentally observed band gap.