The effect of antisite disorder on magnetic and exchange bias properties of Gd-substituted Y$_2$CoMnO$_6$ double perovskite

TL;DR

This study combines experiments and DFT calculations to explore how antisite disorder affects the magnetic properties and exchange bias in Gd-substituted Y$_2$CoMnO$_6$ double perovskite, revealing complex magnetic transitions and significant exchange bias effects.

Contribution

It provides new insights into the influence of antisite disorder on magnetic phases and exchange bias in Gd-doped double perovskites, supported by both experimental and theoretical analysis.

Findings

Paramagnetic to ferromagnetic transition at 95.5 K

Antiferromagnetic transition at 47 K driven by antisite disorder

Large exchange bias effect of 1.07 kOe below 47 K

Abstract

Combining experimental investigations and first-principles DFT calculations, we report physical and magnetic properties of Gd-substituted Y$_2$CoMnO$_6$ double perovskite, which are strongly influenced by antisite-disorder-driven spin configurations. On Gd doping, Co and Mn ions are present in mixed-valence (Co$^{3+}$, Co$^{2+}$, Mn$^{3+}$ and Mn$^{4+}$) states. Multiple magnetic transitions have been observed: i) paramagnetic to ferromagnetic transition is found to occur at \textit{T}$_C$=95.5 K, ii) antiferromagnetic transition at \textit{T}$_N$=47 K is driven by $3d-4f$ polarisation and antisite disorder present in the sample, iii) change in magnetization below \textit{T}$\leq$20 K, primarily originating from Gd ordering, as revealed from our DFT calculations. AC susceptibility measurement confirms the absence of any spin-glass or cluster-glass phases in this material. A significantly large exchange bias effect (\textit{H}$_{EB}$=1.07 kOe) is found to occur below 47 K due to interfaces of FM and AFM clusters created by antisite-disorder.