Weak ferromagnetic interactions of Sm2Fe2O5+δ induced by coupling of the crystal and related lattice vibrations

There is an increase in demand of the next-generation spintronic devices with stable structural and magnetic properties in varying temperatures. An orthoferrites structure of the Pnma space group has been successfully prepared using high temperature solid-state reaction. In the ${\text{Sm}}_2{\text{Fe}}_2{O}_{5+\delta }$ (SFO) material, $F{e}^{3+}$ ions occupy edge-cantered and face-cantered positions forming the tilted $\text{Fe}{O}_6$ octahedrons with Glazer's notation tilt $a^{-}{a}^{-}{c}^{+}$. The ordering of the rare-earth ions at compensation temperature ($T_{\text{comp}}=2.3K)$, spin-flip transition in the range of $9.4-45.6K$, and a second-type spin-reorientation transition around the anisotropy barrier with lower and higher transitional temperatures, $T_L=465$ and $T_H=480K$ respectively. The canting of spins along with disordered spins at the surface results in a non-zero $T_{\text{comp}}$ and unsaturated magnetization. It is inferred that thermal activation of particle's moment over the anisotropy barriers (known as Kneller's law) only occurs above room temperature.