Magnetism of insulator Sr2IrO4 with strong spin–orbit coupling

The magnetic properties of polycrystalline sample Sr2IrO4 have been investigated by the magnetization, electron magnetic resonance (EMR), the infrared (IR) and Raman spectra measurements. Our experimental results indicate that the magnetism is determined by the effective total angular moment Jeff=1/2Jeff=1/2 instead of the spin with S=1/2. The temperature dependence of macromagnetic moment, resonance field of EMR line, A2u mode of IR and A1gA1g mode of Raman spectra exhibit interesting behavior at about 40 K. Due to the Dzyaloshinskii–Moriya interaction, the magnetic order is canted, and the ferromagnetic component decreases with decreasing temperature. These complex magnetic behaviors in the system are attributed to the change of Ir–O–Ir bond angle with cooling, while the variation of bond angle is observed through the IR and Raman spectra.

• We investigate the unusual magnetism of Sr2IrO4 which is dominated by the effective total angular moment Jeff=1/2 rather than the spin with S=1/2.
• The microscopic magnetism of Sr2IrO4 with strong spin–orbit coupling is illustrated by EMR combined with optical measurements.
• The temperature dependence of macromagnetic moment, resonance field of EMR line, A2u mode of IR and A1g mode of Raman spectra exhibit interesting behaviors at about 40 K.