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Phonons correlation with magnetic excitations in weak ferromagnet YCrO3

We report on the temperature dependent Raman spectroscopic studies of orthorombic distorted perovskite YCrO3 in the temperature range of 20-300K. Temperature dependence of DC-magnetization measurement under field cooled and zero field cooled modes confirmed the transition temperature (TN ~142K) and anomalous characteristic temperature (T* ~60K), above which magnetization tends to saturate. Magnetization isotherm recorded below TN at 125K shows clear loop opening without magnetization saturation up to 20kOe, indicating the coexistence of antiferromagnetic (AFM) interaction with weak ferromagnetic (WFM) phase. Mean field calculation for exchange constants further confirms the complex magnetic phase below TN. Temperature evolution of lineshape parameters of selected modes (associated with the octahedral rotation and A-shift in the unit cell) revealed anomalous phonon shift near Cr3+ magnetic ordering temperature (TN ~142K). Additional phonon anomaly was identified at T* ~60K in agreement with the magnetization results and reflects the change in spin dynamics, plausibly due to the change in Cr-spin configuration. Moreover, the positive and negative shift in Raman frequency below TN revel the existence of competing WFM and AFM exchanges. The phonon shift of B3g (3)-octahedral rotation mode fairly scaled with the square of sublattice magnetization from TN to T*, below which it start to depart from theconventional behaviour and need further attention. This correlation between magnetic and Raman data elucidate the spin-phonon coupling owing to the multiferroic phenomenon in YCrO3.