Effect of Annealing and Thickness of Co40Fe40Yb20 Thin Films on Various Physical Properties on a Glass Substrate.

The aim of this work is to investigate the effect of annealing and thickness on various physical properties in Co40Fe40Yb20 thin films. X-ray diffraction (XRD) was used to determine the amorphous structure of Co40Fe40Yb20 films. The maximum surface energy of 40 nm thin films at 300 °C is 34.54 mJ/mm2. The transmittance and resistivity decreased significantly as annealing temperatures and thickness increased. At all conditions, the 10 nm film had the highest hardness. The average hardness decreased as thickness increased, as predicted by the Hall-Petch effect. The highest low-frequency alternative-current magnetic susceptibility (χac) value was discovered when the film was annealed at 200 °C with 50 nm, and the optimal resonance frequency (ƒres) was in the low frequency range, indicating that the film has good applicability in the low frequency range. At annealed 200 °C and 50 nm, the maximum saturation magnetization (Ms) was discovered. Thermal disturbance caused the Ms to decrease when the temperature was raised to 300 °C. The optimum process conditions determined in this study are 200 °C and 50 nm, with the highest Ms, χac, strong adhesion, and low resistivity, which are suitable for magnetic applications, based on magnetic properties and surface energy.

The Influence of Oxidation on the Magnetic, Electrical, and Mechanical Properties of Co40Fe40Yb20 Films.

A typical body-centered cubic (BCC) CoFe(110) peak was discovered at approximately 2θ = 44.7°. At 2θ = 46°, 46.3°, 47.7°, 55.4°, 54.6°, and 56.4°, the Yb2O3 and Co2O3 oxide peaks were visible in all samples. However, with a heat treatment temperature of 300 °C, there was no typical peak of CoFe(110). Electrical characteristics demonstrated that resistivity and sheet resistance reduced dramatically as film thickness and annealing temperatures increased. At various heat treatments, the maximum hardness was 10 nm. The average hardness decreased as the thickness increased, and the hardness trend decreased slightly as the annealing temperature was higher. The highest low-frequency alternative-current magnetic susceptibility (χac) value was discovered after being annealed at 200 °C with 50 nm, and the optimal resonance frequency (fres) was discovered to be within the low-frequency range, indicating that the Co40Fe40Yb20 film can be used in low-frequency applications. The maximum saturation magnetization (Ms) was annealed at 200 °C for 50 nm. Thermal disturbance caused the Ms to decrease as the temperature reached to 300 °C. The results show that when the oxidation influence of as-deposited and thinner films is stronger than annealing treatments and thicker thickness, the magnetic and electrical properties can be enhanced by the weakening peak of the oxide, which can also reduce interference.

Effect of Yttrium Addition on Structure and Magnetic Properties of Co60Fe20Y20 Thin Films.

In this paper, a Co60Fe20Y20 film was sputtered onto Si (100) substrates with thicknesses ranging from 10 to 50 nm under four conditions to investigate the structure, magnetic properties, and surface energy. Under four conditions, the crystal structure of the CoFeY films was found to be amorphous by an X-ray diffraction analyzer (XRD), suggesting that yttrium (Y) added into CoFe films and can be refined in grain size and insufficient annealing temperatures do not induce enough thermal driving force to support grain growth. The saturation magnetization (MS) and low-frequency alternate-current magnetic susceptibility (χac) increased with the increase of the thicknesses and annealing temperatures, indicating the thickness effect and Y can be refined grain size and improved ferromagnetic spin exchange coupling. The highest Ms and χac values of the Co60Fe20Y20 films were 883 emu/cm3 and 0.26 when the annealed temperature was 300 °C and the thickness was 50 nm. The optimal resonance frequency (fres) was 50 Hz with the maximum χac value, indicating it could be used at a low frequency range. Moreover, the surface energy increased with the increase of the thickness and annealing temperature. The maximum surface energy of the annealed 300 °C film was 30.02 mJ/mm2 at 50 nm. Based on the magnetic and surface energy results, the optimal thickness was 50 nm annealed at 300 °C, which has the highest Ms, χac, and a strong adhesion, which can be as a free or pinned layer that could be combined with the magnetic tunneling layer and applied in magnetic fields.

Annealing Effect on the Characteristics of Co40Fe40W10B10 Thin Films on Si(100) Substrate.

This research explores the behavior of Co40Fe40W10B10 when it is sputtered onto Si(100) substrates with a thickness (tf) ranging from 10 nm to 100 nm, and then altered by an annealing process at temperatures of 200 °C, 250 °C, 300 °C, and 350 °C, respectively. The crystal structure and grain size of Co40Fe40W10B10 films with different thicknesses and annealing temperatures are observed and estimated by an X-ray diffractometer pattern (XRD) and full-width at half maximum (FWHM). The XRD of annealing Co40Fe40W10B10 films at 200 °C exhibited an amorphous status due to insufficient heating drive force. Moreover, the thicknesses and annealing temperatures of body-centered cubic (BCC) CoFe (110) peaks were detected when annealing at 250 °C with thicknesses ranging from 80 nm to 100 nm, annealing at 300 °C with thicknesses ranging from 50 nm to 100 nm, and annealing at 350 °C with thicknesses ranging from 10 nm to 100 nm. The FWHM of CoFe (110) decreased and the grain size increased when the thickness and annealing temperature increased. The CoFe (110) peak revealed magnetocrystalline anisotropy, which was related to strong low-frequency alternative-current magnetic susceptibility (χac) and induced an increasing trend in saturation magnetization (Ms) as the thickness and annealing temperature increased. The contact angles of all Co40Fe40W10B10 films were less than 90°, indicating the hydrophilic nature of Co40Fe40W10B10 films. Furthermore, the surface energy of Co40Fe40W10B10 presented an increased trend as the thickness and annealing temperature increased. According to the results, the optimal conditions are a thickness of 100 nm and an annealing temperature of 350 °C, owing to high χac, large Ms, and strong adhesion; this indicates that annealing Co40Fe40W10B10 at 350 °C and with a thickness of 100 nm exhibits good thermal stability and can become a free or pinned layer in a magnetic tunneling junction (MTJ) application.

Impact of Annealing on Magnetic Properties and Structure of Co40Fe40W20 Thin Films on Si(100) Substrate.

Co40Fe40W20 monolayers of different thicknesses were deposited on Si(100) substrates by DC magnetron sputtering, with Co40Fe40W20 thicknesses from 10 to 50 nm. Co40Fe40W20 thin films were annealed at three conditions (as-deposited, 250 °C, and 350 °C) for 1 h. The structural and magnetic properties were then examined by X-ray diffraction (XRD), low-frequency alternative-current magnetic susceptibility (χac), and an alternating-gradient magnetometer (AGM). The XRD results showed that the CoFe (110) peak was located at 2θ = 44.6°, but the metal oxide peaks appeared at 2θ = 38.3, 47.6, 54.5, and 56.3°, corresponding to Fe2O3 (320), WO3 (002), Co2O3 (422), and Co2O3 (511), respectively. The saturation magnetization (Ms) was calculated from the slope of the magnetization (M) versus the CoFeW thickness. The Ms values calculated in this manner were 648, 876, 874, and 801 emu/cm3 at the as-deposited condition and post-annealing conditions at 250, 350, and 400 °C, respectively. The maximum MS was about 874 emu/cm3 at a thickness of 50 nm following annealing at 350 °C. It indicated that the MS and the χac values rose as the CoFeW thin films' thickness increased. Owing to the thermal disturbance, the MS and χac values of CoFeW thin films after annealing at 350 °C were comparatively higher than at other annealing temperatures. More importantly, the Co40Fe40W20 films exhibited a good thermal stability. Therefore, replacing the magnetic layer with a CoFeW film improves thermal stability and is beneficial for electrode and strain gauge applications.

Effect of Annealing on the Structural, Magnetic and Surface Energy of CoFeBY Films on Si (100) Substrate.

The structure, magnetic properties, optical properties and adhesion efficiency of CoFeBY films were studied. Co40Fe40B10Y10 alloy was sputtered onto Si (100) with a thickness of 10-50 nm, and then annealed at room temperature, 100 °C, 200 °C and 300 °C for 1 h. X-ray diffraction (XRD) showed that the CoFeBY films deposited at room temperature are amorphous. Annealing at 100 °C gave the films enough thermal energy to change the structure from amorphous to crystalline. After annealing, the CoFeBY thin film showed a body-centered cubic (BCC) CoFeB (110) characteristic peak at 44°. However, the low-frequency alternative-current magnetic susceptibility (χac) and saturation magnetization (MS) increased with the increase of thickness. CoFeBY thin films had the highest χac and MS after annealing at 300 °C compared to that at other temperatures. After annealing at 300 °C, the surface energy of CoFeBY film is the maximum at 50 nm. Higher surface energy indicated stronger adhesion.

Structure and Magnetic Properties of Co40Fe40V20 Thin Films.

This study investigated the structure and magnetic properties of Co40Fe40V20 thin films with a thicknesses (tf) of 10 nm to 100 nm on a glass substrate. The X-ray diffraction (XRD) patterns of the CoFeV films demonstrated a significant crystalline body-centered cubic (BCC) CoFe (110) structure when the thickness was between 60 and 100 nm, and an amorphous status were shown when the thickness was from 10 to 50 nm. The strongest crystalline XRD peak was at 60 nm because it had a continuous mode of film growth and induced a large grain distribution. The low-frequency alternating current magnetic susceptibility (Ï°ac) property decreased when the frequency increased. The lowest Ï°ac value was detected at 60 nm owing to the large grain distribution inducing high coercivity (Hc) and then enhancing the spin coupling strength. The external field (Hext) was difficult to rotate spin state, then deduces the spin sensitivity and Ï°ac value is decreased. The highest Ï°ac meant the spin sensitivity was maximized at the optimal resonance frequency. The 50-mm thickness had the highest Ï°ac 0.045 value at an fres of 100 Hz. The fres value was less than 1000 Hz at all CoFeV thicknesses, suggesting that CoFeV films would be suitable for low-frequency magnetic component applications. Moreover, the saturation magnetization (Ms) revealed a thickness effect when the thicknesses had a larger Ms. The Hc values were between 3 Oe and 10 Oe at all CoFeV films, except for 60 nm. The Hc of the 60 nm film was about 80 Oe due to the larger grain distribution, and it induced strong remanent magnetization (Mr) and a larger squareness ratio (Mr/Ms) of 92%. The results of the magnetic measurement showed that the 60 nm Co40Fe40V20 film had greater Hc and a good squareness ratio.

Ta and Ru Seed Layers Effect on the Crystallinity and Wettability of Co60Fe20V20 Films.

The following structures are deposited under the conditions (a) glass/Ru(X nm)/Co60Fe20V20(5 nm) and (b) glass/Ta(Y nm)/Co60Fe20V20(5 nm) at room temperature (RT), where X and Y is from 5 nm to 10 nm. X-ray diffraction (XRD) patterns of glass/Ru(X nm)/Co60Fe20V20(5 nm) and glass/Ta(Y nm)/Co60Fe20V20(5 nm) reveal a weak crystallization at peak ß-(200) as the thicknesses of Ta increase from 8 nm to 10 nm, and the patterns indicate an amorphous state as the thicknesses of all Ru films and Ta thicknesses increase from 5 nm to 7 nm. The average contact angles of glass/Ru(X nm)/Co60Fe20V20(5 nm) and glass/Ta(Y nm)/Co60Fe20V20(5 nm) are less than 90° with testing liquids deionized (DI) water and glycerol. The average contact angle of water on the surface is nearly 90 degrees, indicating it is hydrophobic. Moreover, the maximum surface energy of glass/Ru(9 nm)/Co60Fe20V20(5 nm) and glass/Ta(10 nm)/Co60Fe20V20(5 nm) are 44.5 mJ/m2 and 37.4 mJ/m2, demonstrating that the high surface energy corresponds to a strong adhesion, which can be combined with a magnetic tunneling layer of MgO or AlOx and is compatible with other semiconductor processes in magnetic recording media and photoelectric applications.

Microstructure, In-Plane Magnetic Properties, and Surface Energy of Co60Fe20V20 Thin Films.

Co60Fe20V20 thin films with thicknesses ranging from 3 to 13 nm were sputtered onto a Si(100) substrate at room temperature (RT). Captured selected-area diffraction patterns (SADs) and high-resolution cross-sectional transmission electron microscopy (HR X-TEM) images revealed that the microstructures of the Co60Fe20V20 thin films were amorphous. The hysteresis loop of the thinner Co60Fe20V20 thin films displayed the in-plane magnetic anisotropy, possibly as a result of atmo-spheric exposure. A comparison of saturation magnetization (Ms) and thicknesses indicated a concave-down phenomenon due to magnetic coupling. In addition, the coercivity (Hc) also suggested a concave-down trend because the thinner Co60Fe20V20 thin films had a greater pining sites effect and rendered the domain wall difficult to move, resulting in higher Hc and lower Ms. The contact angles were smaller than 90°, indicating that the films were hydrophilic. The surface energy, which had a close positive correlation with adhesion ranged from 22.3 to 33.3 mJ/mm2 and displayed a concave-up trend. The critical thickness was 5 nm. Based on the magnetic and surface energy results, the optimal thickness of Co60Fe20V20 films is 7 nm due to high Ms, low Hc, and strong adhesion. They are suitable for use as a free layer of the magnetic tunneling junction and can be applied in magnetic recording media.

Anomalous Tunnel Magnetoresistance and Spin Transfer Torque in Magnetic Tunnel Junctions with Embedded Nanoparticles.

The tunnel magnetoresistance (TMR) in the magnetic tunnel junction (MTJ) with embedded nanoparticles (NPs) was calculated in range of the quantum-ballistic model. The simulation was performed for electron tunneling through the insulating layer with embedded magnetic and non-magnetic NPs within the approach of the double barrier subsystem connected in parallel to the single barrier one. This model can be applied for both MTJs with in-plane magnetization and perpendicular one. We also calculated the in-plane component of the spin transfer torque (STT) versus the applied voltage in MTJs with magnetic NPs and determined that its value can be much larger than in single barrier system (SBS) for the same tunneling thickness. The reported simulation reproduces experimental data of the TMR suppression and peak-like TMR anomalies at low voltages available in leterature.

Surface-structure-assisted chaotic mode lasing in vertical cavity surface emitting lasers.

We demonstrate chaotic mode lasing in vertical cavity surface emitting lasers at room temperature, with an open cavity confined laterally by the native oxide layer. Instead of introducing any defect mode, we show that suppression of lower-order cavity modes can be achieved by destroying vertical reflectors with a surface microstructure. Lasing on chaotic modes is observed directly through collecting near-field radiation patterns. Various vertical emission transverse modes are identified by the spectrum in experiments as well as numerical simulations in real and phase spaces.