Dual-mode ferromagnetic resonance in an FeCoB/Ru/FeCoB synthetic antiferromagnet with uniaxial anisotropy

• Published in: Applied physics letters Vol. 112; no. 19
• Main Authors: Wang, Cuiling, Zhang, Shouheng, Qiao, Shizhu, Du, Honglei, Liu, Xiaomin, Sun, Ruicong, Chu, Xian-Ming, Miao, Guo-Xing, Dai, Youyong, Kang, Shishou, Yan, Shishen, Li, Shandong
• Format: Journal Article
• Language: English
• Published: 07.05.2018
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5018809

Dual-mode ferromagnetic resonance is observed in FeCoB/Ru/FeCoB trilayer synthetic antiferromagnets with uniaxial in-plane magnetic anisotropy. The optical mode is present in the (0–108 Oe) magnetic field range, where the top and bottom layer magnetizations are aligned in opposite directions. The strong acoustic mode appears, when the magnetic field exceeds the 300 Oe value, which corresponds to the flop transition in the trilayer. Magnetic field and angular dependences of resonant frequencies are studied for both optical (low-field) and acoustic (high field) modes. The low-field mode is found to be anisotropic but insensitive to the magnetic field value. In contrast, the high field mode is quasi-isotropic, but its resonant frequency is tunable by the value of the magnetic field. The coexistence of two modes of ferromagnetic resonance as well as switching between them with the increase in the magnetic field originates from the difference in the sign of interlayer coupling energy at the parallel and antiparallel configurations of the synthetic antiferromagnet. The dual-mode resonance in the studied trilayer structures provides greater flexibility in the design and functionalization of micro-inductors in monolithic microwave integrated circuits.