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The current-driven magnetization switching in CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with various free layer materials including synthetic structure was studied in this paper. The MTJ films were deposited on SiO2/Si substrates using RF magnetron sputtering. The tunnel magnetoresistance (TMR) ratios and current-voltage (I-V) characteristics of the the MTJs were measured at room temperature...
A detailed characterization and analysis of the microwave properties of a set of nanogranular (Fe0.7Co0.3)71B22Ni7 films under an applied magnetic dc field ranging from 0 to 45 kA/m is presented. A full microwave characterization of the films is performed up to 20 GHz using a vector network analyzer (VNA) connected to a matched microstripline or coplanar waveguide, loaded with the films. The evolution...
Summary form only given. This paper focuses on the possibility of direct casting miniature NdFeB-based bulk permanent magnets in different three-dimensional shapes for various applications, with amorphous structure followed by subsequent optimal annealing. Nd3Dy1Fe66Co10B20 bulk nanocomposite permanent magnets in form of rods with diameters ranging from 0.5 to 0.8 mm have been prepared by devitrification...
For toggle MRAM, the free layer is a synthetic antiferromagnet (SAF) that must have specific magnetic properties such as: low magnetostriction, a repeatable saturation field (Hsat) that can be adjusted within a specific range, and a well-defined and reproducible intrinsic anisotropy axis. The results from fully-functional Mb-scale MRAM circuits using CoFeB SAF free layers optimized for toggle switching...
In this paper, the authors have reported a new directional coupler for the cellular phones with an operating frequency of 0.8-2 GHz, which consisted of a coupled microstrip structure with an amorphous CoFeB magnetic thin film and a polyimide dielectric film.
The soft under layer (SUL) is used to improve write head filed strength, field gradient and read-back signal in perpendicular magnetic media. In this study, four type SUL structures were fabricated. Samples were post-annealed and cooled to room temperature under magnetic field along radial direction. VSM, MFM and Guzik spin stand were used to analyze the magnetic properties, domain structure and noise...
In this study, we investigated the TMR effects in CoFeB/MgO/Heusler alloys (Co2FeSi and Co2MnSi) magnetic tunnel junctions. Both Co2FeSi and Co2MnSi heusler alloys have half-metallic band structure and high Curie temperature of 1200K and 985K, respectively. Moreover, the lattice mismatch between the Heusler alloys and MgO barrier is relatively small, which indicates that the highly textured Heusler...
In this report, we will demonstrate that by simply using a bilayer capping layer of Ru/Ta instead of usually used Ta, the switching field, as well as distribution of switching fields, of magnetic tunnel junctions (MTJ) can be considerably reduced. Two samples with the same MTJ stack of Ta/PtMn/SAF-pinned/AlOx/CoFeB(2 nm) (bottom to top) but capped by different metal layers of Ta and Ru/Ta, correspondingly,...
Increasing the frequency of electro-magnetic devices has been continuously pushing magnetic materials to operate over several GHz ranges.The permeability measurement of magnetic thin films were performed by both a broadband CPW and a network analyzer (0.1 -20 GHz) and Ryowa permeameter based on a single turn strip loop. The CPW was designed to have near 50Omega impedance, matching the network analyzer...
CoFeB layer with amorphous structure has attracted much attention due to its soft magnetic properties and the realization of large tunnel magnetoresistance (TMR) ratio at room temperature when used as the free layer in ferromagnet/insulator/ferromagnet magnetic tunnel junctions. Two types of multilayer films were prepared in this study. Type I is a full stack of MTJs to evaluate the transport properties,...
This paper investigates the relationship between the tunneling magnetoresistance (TMR) ratio and the structure of MgO-based MTJs with crystallized CoFeB layers by annealing having CoFe/Ru/CoFeB synthetic ferrimagnet (SF) pin layers with varying Ru spacer thicknesses (tRu). When annealing temperature Ta is lower than 325degC, the Ta dependences of the TMR ratio are similar among all the MTJs. However,...
In this paper, we have fabricated and studied the bias dependence of magnetic tunnel junctions based on a CoFeB / MgO / CoFeB tri-layer structure. These structures exhibit TMR ratios as high as 236% at room temperature. Furthermore, we have observes a weakened dependence of TMR on bias voltage in these structures, with the MR ratio decaying to one half of the zero-bias value at an applied voltage...
This paper aims to investigate the magnetic and electrical properties of magnetic tunnel junctions with MgO barriers. The magnetoresistance of the junction is measured at 0.4 V. Results show a magnetoresistance of almost the same values at varying radical oxidation time and Mg thickness. It is also confirmed in this study that the MgO formed by radical oxidation of Mg shows high magnetoresistance...
Soft magnetic alloys have useful DC properties such as high saturation magnetization, low coercivity, and good mechanical stability.However, for applications at frequencies in the MHz range, eddy currents and increased loss impose serious limitations. By forming polymer composites with separated particles of these magnetic alloys, it is expected that losses can be reduced at these frequencies. In...
The magnetic properties bulk nanograin composite Nd-Fe-B/Fe-Co magnets is enhanced reducing the size and improving the distribution of the soft phase throughout the magnet. This was achieved through various coating technologies applied to coat melt-spun micrometer-sized Nd-Fe-B powder particles with thin alpha-Fe or Fe-Co layers. These coating techniques include sputtering, pulsed laser deposition,...
The thermomagnetic analysis of a hybrid Pr2(Fe,Co)14B/Pr(Co,Fe)5 magnet has revealed that two major events take place at 505degC and 975degC. Most likely, the 505degC event is the Curie temperature of a main phase, while the 975degC event is the Curie temperature of a minor phase. In addition, a few minor events were detected at 313, 772, and 872degC, indicating that hybrid magnets may have complex...
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