In situdetection of two ferromagnetic resonance modes in coupled Ni/Cu/Co/Cu(001) trilayer structures

Unique properties of microwave in interlayer exchange-coupled trilayer ferromagnetic films associated with negative imaginary part of permeability

“…Apparently, for permittivity, there are e 0 o0 and e 00 b|e 0 |, thus the electric damping angle a e has p/2oa e op and a e Ep/2. On the other hand, oscillation of the two magnetizations has two resonance frequencies of 1.00 GHz for acoustic mode and 1.10 GHz for optic mode, respectively [25][26][27]. It is well known that, usually, imaginary parts of both permeability and permittivity are not smaller than zero.…”

“…1, which consists of two ferromagnetic layers separated by a nonmagnetic spacer. Conventionally, the single magnetization vector M * 1 (or M * 2 ) is used to represent behavior of magnetic moment in the first (or second) ferromagnetic layer, and the energies involved in the exchange-coupled trilayer film are taken as [25][26][27] …”

“…It is proposed that, in the low side of resonance frequency, metallic ferromagnetic films are promising for potential applications in magnetic storage media and microwave devices [16][17][18], and near high side of resonance frequency, the metallic ferromagnetic structures may be deemed to be the naturally occurring left-handed materials [19][20][21]. For layered metallic ferromagnetic structures, interlayer exchange coupling (IEC) between the magnetic layers mediated by nonmagnetic spacers is believed to be one of the key factors for many properties observed in magnetic/nonmagnetic artificial structures [22][23][24][25][26][27]. It is also found that the permeability of trilayer (or multilayer) film may be remarkably influenced by IEC [24][25][26][27].…”

“…For layered metallic ferromagnetic structures, interlayer exchange coupling (IEC) between the magnetic layers mediated by nonmagnetic spacers is believed to be one of the key factors for many properties observed in magnetic/nonmagnetic artificial structures [22][23][24][25][26][27]. It is also found that the permeability of trilayer (or multilayer) film may be remarkably influenced by IEC [24][25][26][27]. For instance, in trilayer ferromagnetic film, the imaginary part of permeability of one ferromagnetic layer is unusually smaller than zero near resonance frequency of optic mode [27], i.e., the ferromagnetic layer may be taken as an active medium, and used to demonstrate unique electromagnetic properties predicted previously [13][14][15].…”

Ferromagnetic resonance and magnetization studies in exchange-coupled NiFe/Cu/NiFe structures

“…Although a lot of work has been done applying the FMR technique for investigation of trilayer systems [2,8], there still remain open questions, mainly related to the uniaxial anisotropy of each layer. Lindner et al [9] studied in situ the FMR phenomenon for Ni/Cu/Co(0 0 1) structures, where the in-plane precession modes were studied as a function of temperature. Detailed study of the out-of-plane FMR variations for such structures, however, is still lacking.…”