Investigation of correlation between spin dynamics and lattice degree of freedom in Mott insulator Sr2IrO4

The polycrystalline Sr2IrO4 has been studied using Raman spectroscopy and magnetization. The magnetizationmeasurement confirms canted antiferromagnetic transition below TN= 240 K. Temperature dependent Raman spectroscopic study on Sr2IrO4 has been carried out down to 90 K to investigate the correlation among vibrational and spin degree of freedom. We specifically investigated Ir-O-Ir vibrations (R2 mode) which is related to octahedral tilt as well as exchange interaction. Anomalous hardening of R2 mode below Neel temperature is observed and the deviation of the phonon frequency from the anharmonic behavior is shown to scale with the square of the reduced magnetization.