Nanocrystalline Magnetic Films Research Articles

Numerical calculation of high frequency magnetic susceptibility in thin nanocrystalline magnetic films

Two numerical micromagnetic methods most suitable for calculation of the high frequency magnetic susceptibility of nanocrystalline thin films were considered in detail. The methods are based on the Landau–Lifshitz equation, linearized around the equilibrium state leading to an eigenvalue problem or solved using an undetermined coefficients technique. An analysis and estimation of an efficiency of the methods were carried out. Several conclusions about their advantages and shortcomings, as well as specifics of their practical application were drawn.

Synthesis and Characterization of Co-Fe Nanocrystalline Magnetic Films Electrodeposited From Electrolyte Solution Containing Sodium Saccharin

Cobalt-iron (Co-Fe) alloy thin films ( Co100-x-Fex with x=0 , 6, 11, 14 and 18) were electrodeposited on brass substrates from sulfate plating baths containing saccharin salt. The electrolyte in the synthesis process consists of mixtures of FeSO4.7H2O , CoSO4.6H2O , NaCl and H3BO3 . Various concentrations of FeSO4 were added to the plating solution to deposit films with different alloy compositions. Saccharin (C6H4CONHSO2) was also added as a grain refining agent to improve the quality of deposits. Energy dispersive X-ray spectroscopy (EDS) analyses showed that the compositions of the electrodeposits corresponded to the concentration of FeSO4 in the electrolytic bath. X-ray diffraction (XRD) results showed that the crystallographic structure of the films was dependent on the composition of the alloy. Calculation of crystallite size from X-ray peak broadening showed that the crystallite sizes were within the range of 10-99 nm. Scanning electron microscopy (SEM) results showed that films with higher Fe content exhibited irregular granule shapes. The thicknesses of the thin films were about 50 μm as determined by SEM measurements of the films' cross section. Atomic force microscopy (AFM) results showed rougher granular surfaces for Co-Fe films with higher Fe content. A similar behavior was observed by SEM. Magnetic force microscopy (MFM) showed that the domain pattern was stripe structure for Co and Co94-Fe6 films. The structure changed to granular domain structures with increasing iron content. The best soft magnetic properties with high saturation magnetizations and low coercivities were obtained when BCC and FCC phases of Co-Fe system coexisted.

Nanosecond magnetization reversal in nanocrystalline magnetic films

This paper reports on the investigation of dynamic magnetization reversal process in electrodeposited nanocrystalline Ni and Ni80Fe20 films by employing nanosecond magnetic pulse technique. The surface morphology has been investigated using SEM, EDAX, XRD and AFM analyses and static magnetic properties of the films are characterized by vibrating sample magnetometer (VSM). Two different techniques are designed and employed to study the nanosecond magnetization reversal process in nanocrystalline thin films: Magneto-Optical Kerr Effect (MOKE) and nanosecond pulsed field magnetometer. Results of dynamical behavior as a function of several variables such as magnitude of applied bias magnetic field, amplitude and width of the pulsed magnetic field are analyzed in detail using both techniques. A computer simulation package called Object Oriented Micro-Magnetic Framework (OOMMF) has been used to simulate the magnetic domain patterns of the samples.

Fabrication of Magnetic SmFe Films by Pulsed Laser Deposition at 157 nm

By applying a pulsed laser deposition (PLD) technique with a 157-nm molecular fluorine laser, in a novel ablative geometry, nanocrystalline magnetic films were fabricated for the first time to our knowledge from solid Sm/sub 13.7/ Fe/sub 86.3/ targets with 25-mJ laser energy per pulse in 1-atm He background pressure, which is at least one order of magnitude lower than the energy at 248 nm with a KrF laser. The coercivity of the films after annealing at 680/spl deg/C was 0.1 T; in the case when films were fabricated at high vacuum (10/sup -5/ mbar), we did not observe any coercivity, and films were deposited together with ablated droplets of different size, the presence of which reduces the magnetic properties of the films. In both cases the films were deposited on a Si wafer coated with a /spl sim/150-nm-thick Ta layer. At 157 nm, the composition of the magnetic films remains the same as the initial target composition when at 248 nm the ratio of iron to rare earth on the film is higher than on the target.

Nanostructured magnetic films for extremely high density recording

This paper presents recent results on high coercivity, nanocrystalline magnetic films. Elementary models for magnetization decay, thermal stability, and noise are discussed along with requirements on grain size and anisotropy for recording at extremely high areal densities (approaching 100 gigabits per square inch). Characterization of nanocrystalline films by activation-volume measurements and its relationship to nanostructure are emphasized. A number of recently discovered films with high potential for future extremely high density recording are discussed.

高抵抗微結晶磁性薄膜の高周波電気抵抗の測定

The high -frequency electrical properties of high -resistivity nanocrystalline magnetic films were investigated. Fe(Co-Fe)-Hf-O films had a nanostructure consisting of fine-grain bcc Fe(Co-Fe) and amorphous phase Fe-Hf-O. To clarify the high-frequency electrical properties of the nanocrystalline films, we measured their high-frequency resistivities. The electrical resistivities of Fe (Co-Fe)-Hf-O films were nearly constant up to 100 MHz.