When a flow of electron passes through a paramagnetic layer with strong spin-orbit-coupling such as platinum (Pt), a net spin current is produced via spin Hall effect (SHE). This spin current can exert a torque on the magnetization of an adjacent ferromagnetic layer which can be probed via magnetization dynamic response, e.g. spin-torque ferromagnetic resonance (ST-FMR). Nevertheless, that effect in lower frequency magnetization dynamic regime (MHz) where skin effect occurs in high permeability ferromagnetic conductors namely the magneto-impedance (MI) effect can be fundamentally important which has not been studied so far. Here, by utilizing the MI effect in magnetic-ribbon/Pt heterostructure with high transvers magnetic permeability that allows the ac current effectively confined at the skin depth of ~100 nm thickness, the effect of spin-orbit-torque (SOT) induced by the SHE probed via MI measurement is investigated. We observed a systematic MI frequency shift that increases by increasing the applied current amplitude and thickness of the Pt layer (varying from 0 nm to 20 nm). In addition, the role of Pt layer in ribbon/Pt heterostructure is evaluated with ferromagnetic resonance (FMR) effect representing standard Gilbert damping increase as the result of presence of the SHE. Our results unveil the role of SOT in dynamic control of the transverse magnetic permeability probed with impedance spectroscopy as useful and valuable technique for detection of future SHE devices.
Nanoparticles with their specific properties newly have drawn a great deal of attention of researchers [1-3]Yttrium iron Garnet magnetic nanoparticles (YIG-NPs) are promising materials with novel applications in microwave, spintronics, magnonics, and magneto-optical devices.However, achieving stable and remarkable magnetic YIG-NPs has been remaining as a great challenge. In this paper, synthesized YIG-NPs by modifying co-precipitation (MCP) method is reported. Structural and magnetic properties of final products are compared to those of the materials prepared by citrate-nitrate (CN) method. Smaller crystals and particle size have been found by MCP method comparing to that of synthesized by CN method. Using a relatively low annealing temperatures for both sets of samples (~700 °C), the final YIG samples prepared by MCP method show more structural purity than those made by CN method. Higher saturation magnetization (M s ) and lower coercivity (H c ) are observed in MCP YIG sample (23.23 emu/g and 30.1 Oe) than the CN prepared YIG sample (16.43 emu/g and 44.95 Oe). The Curie temperature is measured to be 569 °C for the MCP YIG sample determined from set of M s measurement at different temperatures ranging from 80-600 K. These findings lead to significant improvement in quality of synthesized (synthetic methods) of YIG-NPs.
We show by means of micromagnetic simulations that spin polarizer in nano-contact (NC) spin torque oscillators as the representative of the fixed layer in an orthogonal pseudo-spin valve can be employed to design and to control magnetic droplet soliton nucleation and dynamics. We found that using a tilted spin polarizer layer decreases the droplet nucleation time which is more suitable for high speed applications. However, a tilted spin polarizer increases the nucleation current and decreases the frequency stability of the droplet. Additionally, by driving the magnetization inhomogenously at the NC region, it is found that a tilted spin polarizer reduces the precession angle of the droplet and through an interplay with the Oersted field of the DC current, it breaks the spatial symmetry of the droplet profile. Our findings explore fundamental insight into nano-scale magnetic droplet soliton dynamics with potential tunability parameters for future microwave electronics.
Proximity-induced magnetism (PIM) in graphene (Gr) adjacent to magnetic specimen has raised great fundamental interests. The subject is under debate and yet no application is proposed and granted. In this paper, toward accomplishment of fundamental facts, we first explore the effect of particle size and clustering in the PIM in Gr nanoplates (GNPs)/yttrium iron garnet (YIG) magnetic nanoparticle (MNP) composite. Microscopic analyzes suggest that fine MNPs distributed uniformly on the GNPs have higher saturation magnetization due to the PIM in Gr. We propose that such magnetic plates can thus be used to shield the stray field generated on the surface of magnetic sensors and play a role as a magnetic lens to prevent the field emanating outside the body of magnetic specimen. The GNPs/YIG composites are coated on a magnetic ribbon and proposed for application in magneto-impedance (MI) sensors. We show that such planar magnetic flakes enhance the MI response against the external applied magnetic field significantly. The suggested application can be furthermore developed toward bio-sensing and magnetic shielding in different magnetic sensors and devices.
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