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C-band (around 5 GHz) microwave bandpass filters fabricated on yttrium-iron-garnet (YIG) and Al-doped-YIG ferrite substrates are tuned by an external magnetic field of 0 to 720 Oe. The filters on Al-doped YIG with lower saturation magnetization exhibit lower tuning ranges and sensitivities but reduced insertion losses and expanded bandwidths. The tunabilities of the filters are related to their partial or full magnetization states. Full magnetization states have three regimes: low field, resonance, and high field. The resonance regime cannot be used for bandpass filters. The detailed tuning mechanism is analyzed based on the dynamic magnetization states of magnetic materials. The results will provide a framework for the design of magnetically tunable bandpass filters. [ABSTRACT FROM PUBLISHER]

We investigate the effect of magnetic neighbor interaction on the state behavior of nano-magnetic disks for data storage and computation applications. We have observed and verified that a nano-magnetic disk, with certain dimension, can exist either in the single domain state or in the vortex state depending on the edge-to-edge spacing between the nano-magnetic disks. The experiments were conducted by varying the diameters and thicknesses with respect to edge-to-edge spacing. The dimensions were based on the phase diagram between the single domain state and the vortex state. We have observed nano-magnetic disks spaced far apart from its neighbor, settled in the vortex state and coupled nano-magnetic disks with less spacing settled in the single domain state. This phenomenon was observed for nano-magnetic disks with thickness between 8 nm to 20 nm and diameters between 80 nm to 140 nm. We validated the simulation by fabricating pairs of nano-magnetic disks with a thickness of 10 nm and diameter of 110 nm along edge-to-edge spacing from 20 nm to 260 nm in steps of 20 nm. [ABSTRACT FROM AUTHOR]

Abstract: We have analytically calculated and compared the total magnetic energies of remanent magnetization states of hollow particles to find conditions for single-domain behavior. The size of the particles and the thickness of the spheroidal shell have been systematically varied for different hard and soft magnetic materials and the corresponding phase diagrams of the lowest-energy configurations are derived. [Copyright &y& Elsevier]

• Magnetization states under the spin-transfer effect are elucidated in a Co 1.5 Fe 1.5 Ge nanopillar alloy. • A comparative study has been accomplished by numerically solving the Landau-Lifshitz-Gilbert equation with the Spin-Transfer Torque contributions. • Single-step magnetization switching under weak spin-polarized currents is possible for well-adjusted dimensions. In this work, the magnetization states under the spin-transfer switching effect are investigated in a nanopillar device composed of a half-metallic Heusler Co 1.5 F e 1.5 G e alloy with a four-fold in-plane magnetocrystalline anisotropy. A comparative study with a half-metallic Heusler alloy of Co 2 F e A l 0.5 S i 0.5 and a typical material of Fe is realized by numerically solving the Landau-Lifshitz-Gilbert (LLG) equation with the Spin-Transfer Torque (STT) contribution, using micromagnetic simulations. Our ultimate goal is to elucidate the origins of the intermediate state (IS) that occurs during magnetization switching by deeply examining the effects of magnetocrystalline anisotropy and shape anisotropy on the magnetization states through analyzing and comparing various switching processes. Our simulation results showed that the magnetization switching via a single-step under low current densities is possible at certain critical cross-sectional dimensions of the ellipse that are adjusted to increase the demagnetization field against the four-fold in-plane magnetocrystalline anisotropy. As well, we provided in this paper a set of appropriate geometric dimensions which allow the magnetization to reverse via a single-step by overcoming IS with minimal spin-polarized current densities. [ABSTRACT FROM AUTHOR]

The magnetization state of 1D magnetic nanoparticle (NP) chains plays a key role in a wide range of applications ranging from diagnosis and therapy in medicine to actuators, sensors, and quantum recording media. The interplay between the exact particle orientation and the magnetic anisotropy is in turn crucial for controlling the overall magnetization state with high precision. Here, a 3D description of the magnetic structure of one‐NP‐wide chains is reported. Here, two complementary experimental techniques are combined, magnetic force microscopy (MFM) and electronic holography (EH) which are sensitive to out‐of‐plane and in‐plane magnetization components, respectively. The approach to micromagnetic simulations is extended, which provides results in good agreement with MFM and EH. The findings are at variance with the known results on unidirectional NP assemblies, and show that magnetization is rarely strictly collinear to the chain axis. The magnetic structure of one‐NP‐wide chains can be interpreted as head‐to‐head magnetic domain structures with off‐axis magnetization components, which is very sensitive to morphological defects in the chain structure such as minute size variation of NPs, tiny misalignment of NPs, and/or crystal orientation with respect to easy magnetization axis. [ABSTRACT FROM AUTHOR]