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The exchange-coupling-strength effect on the magnetic properties and noise of laminated [FeCo (t nm)/Rus0.9 nm)]nC(5 nm) films as a magnetic soft underlayer (SUL) for perpendicular recording was investigated. It is found that the remanent magnetization decreases significantly with increasing the exchange-coupling strength, whereas, the coercivity remains almost unchanged. The spike noise is clearly seen in the single layer films without exchange coupling and its peak value is as high as 250 mV. The spike noise is significantly suppressed by introducing antiferromagnetic coupling and even eliminated in the films with strongest antiferromagnetic coupling. The noise peak value can be as low as 25 mV for the films with strongest coupling. The average noise decreases with increasing exchange-coupling strength, but increases linearly with increasing the Mrt of SUL. The noise-reduction mechanism is also discussed. [ABSTRACT FROM AUTHOR]

The microstructure and magnetic properties of (FePt)100-x(MgO)x films annealed at different temperature for different time were investigated. The (FePt)100-x(MgO)x films in situ deposited at 350 °C show (001) preferred orientation. The coercivity increases with the annealing temperature for all films. For FePt and (FePt)95 (MgO)5 films, the coercivity first increases with the increase of the annealing time from 10 to 30 s, but decreases dramatically with further increment of the annealing time. For the FePt-(MgO)10 film, the effect of annealing time on coercivity is not obvious. The domain size decreases with the increase of the MgO content and post-annealing can reduce the domain size effectively. [ABSTRACT FROM AUTHOR]

Multilayered Co-doped TiO2 thin films with postannealing treatment were investigated. Based on x-ray photoelectron spectroscopy, Co(II) binding state was found after annealing. Its intensity increases with the annealing temperature. Postannealing in an ultrahigh vacuum system is an efficient way to drive Co atoms to diffuse into TiO2. It is interesting to find that samples with partial cosputtering structure have a much stronger Co(II) peak than those of pure multilayer structure. Transmission electron microscope patterns show that the annealed films have a polycrystal rutile-TiO2 phase. The saturation magnetization of annealed sample at 150 K is 1.325 uB per Co atom, which is close to the value expected for low-spin Co(II). © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present a simple fabrication of FePt and Fe nanocomposite by annealing self-assembled FePt nanoparticles. 5 nm FePt nanoparticles were prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in the presence of oleic acid and oleylamine as stabilizers. The as-synthesized FePt nanoparticles can self-organize well on a clean SiO/Si substrate and, then, were annealed in a vacuum using a rapid thermal process at different temperatures for 0.5 h. It is found that the annealing temperature plays a key role in determining the final products. The samples annealed at 550 °C and 700 °C consist of a FePt-face-centered-tetragonal (fct) phase with a coercivity of around 1000 and 8800 Oe, respectively, whereas, the samples annealed at 580 °C are composed of two phases: one is the FePt-fct phase and the other is a Fe-body-centered-cubic phase. The hysteresis loop of the sample annealed at 580 °C is also two-phase like with a kink at low field and its coercivity is around 8000 Oe. That indicates that Fe can be segregated from FePt by proper annealing, forming FePt and Fe nanocomposites. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

(Co[SUB60]C[SUB40])[SUB97]Ta[sub3] and Co[sub60]C[sub40] films with thickness 30 nm were prepared by cosputtering Co, Ta, and C onto C-buffered glass substrates. The as-deposited (Co[SUB60]C[SUB40])[SUB97]Ta[sub3] and (Co[sub60]C[sub40] films were amorphous and nonferromagnetic. These films became magnetic upon annealing and the magnetic performance of annealed (Co[SUB60]C[SUB40])[SUB97]Ta[sub3] films are better than that of annealed Co[sub60]C[sub40] films at the same annealing condition. Magnetic patterning (line array) of the as-deposited (Co[SUB60]C[SUB40])[SUB97]Ta[sub3] films was realized by subjecting it to electron-beam radiation using a focused 30 keV beam with a current of 7.1 nA and a dwell time per line of 0.75 s and longer. By increasing the dwell time, the whole region where an electron beam was scanned became magnetic with clear domain structures because of thermally activated diffusion. The required dwell time of magnetically patterning nonmagnetic (Co[SUB60]C[SUB40])[SUB97]Ta[sub3] thin films (0.75 s) is much shorter than that of Co[sub60]C[sub40] films (3.8 s). The magnetic measurements show that the lines [(Co[SUB60]C[SUB40])[SUB97]Ta[sub3]] and dots (Co[sub60]C[sub40]) are magnetically soft. The present method of magnetically patterning a nonmagnetic film has potential application for nanoscale solid magnetic devices. [ABSTRACT FROM AUTHOR]

We present a method of direct magnetic patterning of a nonmagnetic Co-C amorphous film by electron beam radiation induced nano-scale phase transition. Co-C alloy films with C concentration from 30 to 50 at % and thickness of 30-60 nm were prepared by alternately sputtering Co and C films onto C-buffered glass substrates. The films are amorphous and nonmagnetic with C concentration up to 40 at %. Due to their negative mixture entropy, as-deposited amorphous Co-C alloy films are metastable. Focused electron-beam irradiation causes localized phase segregation of the immiscible magnetic (Co-rich) and nonmagnetic (C-rich) phases. Ferromagnetic Co(C) nano-dot array was fabricated by subjecting the as-deposited Co[sub 60]C[sub 40] films to electron beam radiation using a beam current of 16 nA, a beam energy of 20 keV and a dwell time of 5 s per dot. Magnetic force microscopy images and magnetic measurements confirm the formation of the ferromagnetic phase. The present single-step nanolithography eliminates the cumbersome traditional processes and is potentially a new and flexible alternative for fabricating patterned magnetic nanostructures for submicron magnetic devices. [ABSTRACT FROM AUTHOR]

FeCoC granular thin films are prepared and studied as the soft magnetic layer in order to obtain a low noise double-layered perpendicular recording medium. FeCoC granular soft magnetic underlayer prepared by cosputtering at room temperature showed good soft magnetic properties; with coercivity of a few oersteds and B[sub s] of 1.4-1.7 T. Using a spin-stand and a ring-type head, sharper transitions can be obtained in the [Co/Pd][sub n] media with an FeCoC soft underlayer at higher recording density compared to media without a soft magnetic layer. No spike noise was observed in the read back signals for [Co/Pd][sub n] media with an FeCoC granular film as the soft magnetic underlayer. Preparing the [FeCo/C][sub n] laminated films by alternately sputtering FeCo and C layers allows the properties of the films to be flexibly adjusted. A B[sub s] of 1.9 T with relative permeability of 100-400 and coercivity lower than 40 Oe can be obtained with laminated [FeCo/C][sub n] (210 nm) multilayer thin films. [ABSTRACT FROM AUTHOR]

The first-order magnetic phase transition alloy, FeRh, exhibits a large magnetocaloric effect well above room temperature and works in a limited refrigeration temperature region, which hinders its application to some extent. In the present work, we report a remarkable electric-control magnetocaloric effect in the FeRh0.96Pd0.04/PMN-PT composite near room temperature through strainmediated magnetoelectric coupling. By applying an electric field of 8 kV/cm, the metamagnetic phase transition temperature of the FeRh0.96Pd0.04 film shifts from 300 to 325 K. As a result, the refrigeration temperature region is broadened from 35 to 47 K. These results indicate that applying multiple driving fields is an effective method for tuning the magnetocaloric effect. [ABSTRACT FROM AUTHOR]

We have investigated the characteristic properties of Co/Fe multilayers sputtered on Ru underlayer as the field generation layer (FGL) of spin torque oscillator (STO) for microwave assisted magnetic recording. The Co/Fe multilayers exhibit large uniaxial negative anisotropy (up to ~8.7 X 106 erg/cm3), ultra-low damping constant (~0.008), and small in plane coercivity Hc (~5 Oe) that are required for stable STO precession over a wide range of applied magnetic fields and injected spin currents. The importance of Ru underlayer to achieve the above parameters has been addressed. We further show through theoretical calculations that a frequency of 30+ GHz is realistic using Co/Fe multilayers as the field generation layer in a STO comprising a perpendicularly magnetized polarizer and a planar FGL (10-nm Co/Fe multilayers) separated by a metallic spacer. [ABSTRACT FROM AUTHOR]