Microwave Field-Induced Changes in Raman Modes and Magnetic Force Images of Antiferromagnetic NiO Films

Effective control of domain walls or magnetic textures in antiferromagnets promises to enable robust, fast, and nonvolatile memories. The lack of net magnetic moment in antiferromagnets implies the need for creative ways to achieve such a manipulation. We conducted a study to investigate changes in magnetic force microscopy (MFM) imaging and in the magnon-related mode in Raman spectroscopy of virgin NiO films under a microwave pump. After MFM and Raman studies were conducted, a combined action of broadband microwave (0.01-20 GHz, power scanned from -20 to 5 dBm) and magnetic field (up to 3 kOe) were applied to virgin epitaxial (111) NiO and (100) NiO films grown on (0001) Al2O3 and (100) MgO substrates, following which the MFM and Raman studies were repeated. We observed a suppression of the magnon-related Raman mode subsequent to the microwave exposure. Based on MFM imaging, this effect appeared to be caused by the suppression of large antiferromagnetic domain walls due to the possible excitation of antiferromagnetic spin oscillations localized within the antiferromagnetic domain walls.