Co-based Films Research Articles

Activation volumes of wall-motion and nucleation processes in Co-based ferromagnetic multilayer films

Activation volumes of the wall-motion and nucleation processes in Co-based multilayer films were characterized from time-resolved domain evolution patterns. These activation volumes were both sensitive to the multilayer structure as well as the film preparation condition. The two activation volumes were generally unequal with each other and the inequality directly influenced on magnetization reversal behavior.

液体急冷非晶質薄帯上に析出した無電解ＣｏＦｅ系合金めっき膜の析出挙動と性状

Co-based films were deposited electrolessly on rapid-quenched Ni-based amorphous alloy ribbons. Electroless deposition is possible autocatalytically on amorphous substrates when dimethylamine borane (DMAB) is used as the regand agent. A Co-based alloy film with a maximum Fe content of 60at% was obtained by controlling chemical composition in the bath and deposition conditions. Magnetic properties of obtained films depended on surface conditions and the ribbon substrate composition. Changes in film layer structural and magnetic properties with different film thicknesses were observed when bimetals were heat-treated at a range of temperatures that did not crystallize the ribbon.

Magnetic properties of Ni‒Co-based thick films investigated with magnetic force microscopy

Abstract Preliminary results are presented of a magnetic force microscopy (MFM) investigation to characterize Ni-Co-based screen-printed and fired films magnetically. These systems are of interest not only for contactless magnetoresistive sensors of mechanical quantities but also because they are made of micrometre sized grains sintered (and, in the case of Ni plus Co grains, alloyed) during the thermal process. Hence, a detailed study of their magnetic properties has been undertaken. Typical domain structures and zones have been observed by Mfm at resolutions of about 0·2 μm (static mode) and 50 nm (dynamic mode). Changes in the domain structure and deflection forces acting on the magnetic force microscope tips have been observed in samples prepared at various peak firing temperatures, and in samples of different compositions.

Giant Magnetoresistance in (Fe, Co)-X-O (X=Y, Nd, Sm, Gd, Tb, Dy) Nano-Granular Films

We studied the giant magnetoresistance (GMR) and related properties of (Fe, CO)-X-O (X=Y, Nd, Sm, Gd, Tb, Dy) films. The films were prepared by conventional rf sputtering of Fe, CO or Fe-Co, and X2O3 targets. The films seem to have a granular structure composed of nano-size metallic grains and thin oxide boundaries. The films exhibited superparamagnetic properties and high electrical resistivities of 104-106 μΩcm, and had negative and isotropic magnetoresistances at room temperature. The values of Δρ/ρ0 in Co-based films were larger than those of Fe-based films, and a GMR effect of 2.7% at 500 Oe was observed for Co51.0Sm10.7O38.3 The GMR effect film at room temperature. observed in the granular structure is attributed to spindependent tunneling conductance through a thin oxide layer between grains in the film.

Magneto-optical effect in Co-based metallic layered and multilayer films

A preliminary investigation of the magneto-optical effect in Co-based metallic bilayer, trilayer and multilayer films has been carried out in this paper. Various sublayers of non-magnetic materials with different thicknesses were selected. The Kerr enhancement due to the reduction of effective optical constants in Co/Ag bilayers and multilayers has been achieved.

Co-based multilayer films as novel magneto-optical recording media

Co/Pd and Co/Pt multilayer films prepared by e-beam evaporation and DC sputtering have been extensively studied for the development of novel megneto-optical recording media. The films deposited on glass substrates hava a [111] fcc texture and a columnar structure has been observed in the samples prepared by e-beam and sputtering pressures. It was found that the magnetic and magneto-optical properties were much dependent on the sublayer and total thickness of the films as well as on the preparation method. Perpendicular magnetic anisotropy was observed for samples having a thickness of Co smaller than about 6 Å and that of the noble metal larger than about 5 Å. The multilayer films turned out to be extremely stable after thermal cycling and no evidence of interdiffusion between the two constituents was observed after a 100 million writing–erasing cycle at a 9.5 mW laser power and 500 ns pulse duration. Carrier-to-noise ratios (CNR) of 46 and 52 dB at a 780 nm laser wavelength were obtained for Co/Pd and Co/Pt magneto-optical disks, respectively.

Magnetic properties and structure in Co-based nitride thin films

Experimental results on the magnetic properties and structure in Co-based nitride thin films are presented. The high-temperature stability of magnetic softness in Co-based nitride films is shown to originate from crystalline structure with very small dimension, confirmed by small-angle X-ray diffraction and Mossbauer spectroscopy, though only halos are observed in a normal X-ray diffraction experiment. By structure transformation from amorphous to small crystallite magnetostriction changes rapidly and magnetic moment increases. These structures influence magnetic anisotropy induced by field cooling. The anisotropy cannot be controlled below 500 degrees C in the CoZrN films, though by addition of Fe the anisotropy can be controlled up to 350 degrees C. It is suggested that this anisotropy originates from hexagonal-close-packed-like atomic stacking order in the FCC Co crystallite.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The crystallography and texture of Co-based thin film deposited on Cr underlayers

Some of the evidence for the effect of Cr orientation on the crystallographic orientation of Co-based thin films is presented. The authors review four experimental techniques that can be used to investigate the orientation relationships (OR) between the magnetic Co-based film and the Cr underlayer. These techniques are X-ray diffraction, selected area (electron) diffraction (SAD), electron microdiffraction, and atomic resolution electron microscopy of cross sections of the bi-layer films. The authors focus on the crystallographic orientation relationships between the grains in the magnetic film and those in the Cr (BCC) underlayer. The magnetic films discussed are all alloys of Co, usually with HCP structure.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of Irradiation on Amorphous Electrodeposited CoNiP Alloy Films

Experimental studies are made on the effect of hydrogen, boron ions, electrons, and γ-irradiations on thermal stability of amorphous electrodeposited Co-based films using X-ray diffraction, transmission electron microscopy, and magnetic measurements. It is found that all the types of irradiations mentioned above result in a deterioration of the thermal stability of the amorphous state. Under definite conditions of hydrogen ion irradiation the effect of irradiation-induced crystallization of the CoP alloy films is observed. It is assumed that the irradiations studied increase the short-range order in the atomic arrangement of amorphous electrodeposited films, resulting in the activation of the crystalline phase nucleation process. [Russian Text Ignored]

Multilayered films of nitride alloys as magnetic head materials

Multilayered alloy films composed of non-nitride and nitride layers were prepared by N 2 reactive sputtering. Soft magnetic properties were obtained for the films comprising metal-metal elements such as Co-Nb-Zr/Co-Nb-Zr-N when the layer thickness is less than 30 nm and for the films comprising metal-metalloid elements such as Fe-Nb-B/Fe-Nb-B-N when it is less than 60nm. The films showed high 4π M s (12–17kG) and a high permeability (2000–4000 at 1 MHz) after magnetic field annealing at 400–700°C. Magnetic VCR heads manufactured with Co-based multilayered films showed extremely high efficiency both in recording and reproducing characteristics.

Ｃｏ基合金・窒化物複合分散型アモルファス膜の磁気特性

In an effort to get an excellent magnetic thin film for micro inductance cores, amorphous Co-based films with dispersed fine nitrides were investigated. Amorphous structure, almost zero magnetostriction (λ) and high electrical resistivity were confirmed in the sputter deposited films. TEM observation clarified that these films were composed of two kinds of amorphous phases. Soft magnetic properties of the obtained films were found to be related to the thickness of the film; as the thickness becomes less than 0.1 μm, the films become magnetically soft. Based on this relation, we attempted to make multilayered films consisting of the Co-based thin layers and BN ceramics thin layers and obtained excellent properties with high ρ (>300μΩcm), lowλ (1×10-6 ) and high μ ( > 1000) at high frequency near 100 MHz.

Co-based superstructured nitride alloy films: characteristics and applications for high frequency heads

Co-based superstructured films composed of 25-nm-thick non-nitride and nitride layers were prepared by N/sub 2/ reactive RF sputtering. The films have high 4 pi M/sub s/=13 kG, a high permeability mu =3000, and a high thermal stability of the magnetic properties. Magnetic heads composed of laminated superstructured films insulated with SiO/sub 2/ films were developed for high-frequency operations. The heads show excellent recording capability for narrow gap recording with metal tapes and high reproduction characteristics at frequencies over 10 MHz. They achieve an increase of more than 4 dB in normalized output when compared with conventional laminated-type amorphous film heads. The superstructured nitride film heads are expected to be used in next-generation VCRs, which operate with higher density recording and wider frequency bands. >

The TM dependence of the magneto-optic signal in GdTb-TM thin films

The magneto-optic polar Kerr rotation for various GdTb-TM thin films was measured at room temperature as a function of TM composition and was found to correlate with the Slater–Pauling curve. In spite of the fact that the temperature dependence of magnetization is a complicating factor, the data clearly establish the above-mentioned correlation. The TM compositions ranged from Mn through Fe and Co to Ni. The Fe-based films had Curie temperatures covering a range from 100 to 300 °C in contrast to the Co-based films whose Curie temperatures were clearly much greater than 300 °C. Neither the Mn- nor the Ni-based films exhibited desirable magneto-optic activity when fabricated under the same conditions as the Fe- and/or Co-based films. When the Fe constituent of the GdTbFe films was gradually substituted with Mn or Co the room-temperature magneto-optic signal was found to decrease and increase, respectively. In a similar manner, when the Co constituent of GdTbCo films was gradually substituted with Fe or Ni the room-temperature magneto-optic effect was found to increase and decrease, respectively. However, when the Co constituent of GdTbCo films was gradually substituted with Mn the room-temperature magneto-optic effect also decreased, clearly establishing the correlation to the Slater–Pauling curve. These results are further evidence that the magneto-optic effect of traditional RE-TM thin films is dominated by the TM composition and explain the fact that the magneto-optic signal is largest in GdTbFeCo thin films. New data supporting the correlation between magneto-optic effect and perpendicular anisotropy was also obtained.