Soft magnetic properties of composite-anisotropy CoNbZr/ceramics multilayers (invited)

Abstract

CoNbZr/ceramics multilayered films, the metal layers of which have sequentially changed anisotropy directions, were investigated. Such newly processed film is called ‘‘composite-anisotropy multilayer film.’’ The effects of this new processing on soft magnetic properties were studied. In the case where the shift angle in the easy magnetization direction between neighboring CoNbZr layers is 45°, a smooth B-H loop with low coercivity was obtained. Furthermore, annealing from 200 to 400 °C resulted in high permeability (μ′) of 1000–1500 and excellent frequency responses of μ′ above 100 MHz in all directions in the plane of the film. These results could be explained in terms of magnetic interactions of the CoNbZr magnetic layers which are in close contact with one another across the intervening ceramics layers. These findings indicate that such composite film has many advantages over conventional uniaxial multilayers in applications to magnetic devices. Since these characteristics are thought to be very significant for microdevices composed of disc-shaped magnetic cores, we fabricated a planar microtransformer composed of circular spiral coils and disk-shaped magnetic cores, 2.4 mm in size, using photolithographic technology. The input–output voltage ratio, VOUT/VIN, was measured in the frequency range of 2–40 MHz and showed a high value of 0.83 at 40 MHz.

E-Field Tuned Rotation of Magnetic Anisotropy and Enhanced Microwave Performance in FeCoAlO/PZN–PT Multiferroic Composite Prepared by Composition Gradient Sputtering

“…For example, a high permeability is only available when excitation magnetic field is along the magnetic hard-axis (HA) direction, i.e. HA excitation [16]- [18]. This restricts the efficiency of SFMs to only 50% for the UMA SFMs when the SFMs cover on the plane of microinductors.…”

“…For this purpose, Sugawara et al [16] fabricated composite anisotropy multilayer films using the multilayering method in which many magnetic thin layers with constant uniaxial anisotropy were piled up with the anisotropic axes being shifted sequentially from bottom to surface so as to cancel out the overall anisotropy [16]. Chai et al [19] reported an omnidirectional rotatable anisotropy in ferrite doped CoFe thin film.…”

In-plane Isotropic Microwave Performance of CoZr Trilayer in GHz Range

“…To find the desired materials with IHP in the GHz range is still a challenge. For instance, a variety of theoretical 5 6 7 and experimental works focus on both high 8 9 10 and isotropic 11 12 13 14 15 16 17 18 permeability in the GHz range of granular films 9 and multilayers 10 of magnetic alloys, ferrites and their composites.…”

“…Searching for the isotropic permeability in the GHz range is another important topic in magnetic thin films. For instance, magnetic thin films with rotatable stripe domain 42 43 44 45 46 , composite-anisotropy multilayer as well as crossed anisotropies multilayer 11 12 13 14 15 16 17 18 are intensively investigated. The rotatable stripe domain was discovered firstly in Permalloy films in 1961 42 , and then in many other magnetic thin films 43 44 45 46 .…”

High noise suppression using magnetically isotropic (CoFe-AlN)/(AlN) multilayer films

“…3 In recent decades, high-frequency soft magnetic thin films have been extensively studied because of their potential suitability as noise suppressors for ultrasmall integrated circuit chip modules. In particular, Co alloy amorphous films 4,5 and Co metal-oxide granular films 3,6 have attracted significant attention owing to their high saturation magnetization and soft magnetic properties at high frequencies. These conventional films exhibiting uniaxial magnetic anisotropy have shown high-frequency soft magnetic performance, which unfortunately degraded when the effective electromagnetic field direction deflected from its hard axis, limiting their application to uniaxial devices.…”