Modulation of spin reorientation and exchange bias in SmMn0.25Fe0.75O3 orthoferrite single crystal

Futuristic multi-state storage devices and energy-efficient data storage sensors depend on advanced functional materials that manifest both spin and charge ordering. Here, we report the growth of SmMn_0.25Fe_0.75O₃ (SMFO) single crystals, which crystallize in an orthorhombic structure (space group: Pbnm), as determined through measurements of temperature-dependent X-ray diffraction (XRD). The SMFO crystals display varying physical properties due to modulation of the spin reorientation transition (SRT) Γ₄ → Γ₂ at 382 K, which is relatively lower than the 450 K transition reported in pristine SmFeO₃. Moreover, the addition of Mn (25 %) induces a new spin reorientation (T_SR1: Γ₂ → Γ₁) occurring at 175 K. The observed exchange-bias effect in the SMFO crystal shows a divergence at the onset of spin reorientation temperature. The spin canting angle in SMFO is characterized within the context of mixed ferromagnetic and antiferromagnetic domains. We further elaborate direct correlation between anisotropic lattice compression and the spin canting angles. The mutual competing 3d-3d and 3d-4f spin exchange interactions between the magnetic moments of Sm³⁺ ions and Fe³⁺ (Mn³⁺) ions, which results in minimal lattice distortions that break inversion symmetry. This leads to the Dzyaloshinskii-Moriya (D-M) interaction that further induces a net electric dipole moment. These experimental findings indicate that competing exchange interactions are crucial in controlling the exchange bias, spin-anisotropy, lattice distortion, and ferroelectricity, which are beneficial for the development of functional devices and their applications.