Magneto-structural correlation across the spin reorientation transition temperature in pure and Sm substituted TmFeO3: A temperature dependent Raman and synchrotron X-ray diffraction study

This paper presents the magneto-structural study on orthoferrite TmFeO3 and Sm substituted TmFeO3 across spin reorientation transition (SRT) temperature. A strong change in magnetic anisotropy due to the substitution of the Sm3+was observed, which is reflected as a change in spin reorientation transition (SRT) temperature. The SRT temperature of Tm0.5Sm0.5FeO3is found to be around 200–230 K, which is relatively high in comparison to TmFeO3. A sudden decrease in the value of coercivity has been observed in the SRT region for both the sample. The lattice dynamics of TmFeO3 and Tm0.5Sm0.5FeO3were investigated by temperature-dependent x-ray diffraction and Raman spectroscopy. We observed unusual contractions in the lattice parameter at low temperatures due to complex exchange interaction between RE3+ and Fe3+ ions sub-lattice. Anomalous behavior in lattice parameters was observed in the vicinity of SRT, which confirms the system's spontaneous magnetostriction.The strong anomaly was observed in line width and phonon frequency of Raman modes of around SRT, which established the spin-lattice coupling in TmFeO3 and Tm0.5Sm0.5FeO3 nanoparticles. Observation of spin-lattice coupling utilizing Raman scattering substantiates our magnetic and structural correlation and supports its candidature for magneto-elastic applications.