© 2020 The Japan Society of Applied Physics. In this study, we fabricated quasi-Antiferromagnetic (AFM) layers and investigated the magnetic dynamics of quasi-AFM in both an experiment and simulation. Quasi-AFM has multi domains with alternating antiparallel magnetization, which can be realized by using 90° magnetic coupling between two ferromagnetic layers. In magnetic resonance measurement, a frequency and damping constant of CoFe-based quasi-AFM are higher than those of conventional CoFe. Likewise, in micromagnetic simulation, we obtained the spin torque oscillation in Quasi-AFM with high frequency. This suggests the possibility of a novel material with the high frequency wave generator without a stray field, like antiferromagnetic materials.