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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Magnetic characteristics of ultrathin Fe films with Ar bombardment during and after deposition

S. Iwatsubo and M. Naoe

J. Appl. Phys. 93, 7193 (2003); http://dx.doi.org/10.1063/1.1555899 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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The three kinds of Fe films, without Ar bombardment (BNON), with Ar bombardment after deposition (BAFT), and with Ar bombardment during deposition (BDUR) were prepared by dual ion beam sputtering. The relationship between the morphology and the magnetic characteristics of the Fe films has been investigated as a function of the film thickness tF in the wide range between 0.5 and 600 nm. The sputtering voltage and current were fixed at 1200 V and 50 mA, respectively. The Ar bombardments for BAFT and BDUR were carried out at the ion acceleration voltage of 200 V for the period. The features of the film growth were very different among them. The films of BNON changed from island structure to layer structure at tF between 8 and 16 nm. The films of BAFT and BDUR revealed smoother surfaces than that of BNON and were in layer structure at tF above 1 nm. However, the saturation magnetization 4πMS of BDUR abruptly decreased at tF below 8 nm, since the Ar bombardment knocked Fe atoms into the surface region of glass substrate at the initial growth stage. On the other hand, 4πMS of BNON and BAFT took almost constant value of 21.5 kG with a fluctuation of about 5%. The coercivity HC of BAFT took the minimum value among them at tF below 4 nm. These results indicate Ar bombardment after the deposition is useful for preparing the ultrathin Fe films with excellent soft magnetic properties. © 2003 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.05.Bx Metals, semimetals, and alloys
81.15.Cd Deposition by sputtering
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetic nanoparticles of Fe2O3 synthesized by the pulsed wire evaporation method

Y. R. Uhm, W. W. Kim, S. J. Kim, C. S. Kim, and C. K. Rhee

J. Appl. Phys. 93, 7196 (2003); http://dx.doi.org/10.1063/1.1558234 (3 pages) | Cited 17 times

Online Publication Date: 9 May 2003

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Nanoparticles of Fe2O3 with a mean particle size of 4–50 nm have been prepared by the pulsed wire evaporation method, and its structural and magnetic properties were studied. From the main peak intensity of x-ray diffraction the amount of ɣ-Fe2O3 and ɑ-Fe2O3 in sample is composed about 70% and 30%, respectively. The coercivity (53 Oe) and the saturation magnetization (14 emu/g) are about 20% of those of the bulk ɣ-Fe2O3. A quadrupole line on the center of Mössbauer spectrum represents the superparamagnetic phase of ɣ-Fe2O3 with a mean particle size of 7 nm or below. © 2003 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
81.07.Bc Nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
76.80.+y Mössbauer effect; other γ-ray spectroscopy
61.46.-w Structure of nanoscale materials

Structural effects on the magnetic character of yttrium–iron–garnet nanoparticles dispersed in glass composites

Susamu Taketomi, Alexander J. Shapiro, and Robert D. Shull

J. Appl. Phys. 93, 7199 (2003); http://dx.doi.org/10.1063/1.1555900 (3 pages)

Online Publication Date: 9 May 2003

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By absorbing amorphous yttrium–iron–garnet nanoparticles into nanometer pores of the sponge-like structure of porous silica glass [controlled pore glass (CPG)] followed by heat treatment, we obtained dispersed-nanocrystal/glass composites. We prepared samples using different extremal heat treatments: low temperature long calcination (700 °C, 2 h) and high temperature short calcination (1000 °C, 0.1 h). From the difference between the secondary electron image in a field emission scanning electron microscope (FESEM) and the backscattered electron image of the same sample surface area, it is concluded that the nanoparticles were imbedded on and just beneath the surface of the CPG granules. This was confirmed by a cross-sectional backscattered electron image of the sample in the FESEM. In this image nanoparticles of 20–40 nm were monodispersed in a 2 μm thick shell of fused glass and, inside this shell, the inner core of CPG granules preserved their sponge-like structure and contained no nanoparticles. Powder x-ray diffraction revealed that the synthesized nanoparticles were dominantly ϵ-Fe2O3, however, many small diffraction peaks consistent with those of Fe5Y3O12 and FeYO3, were also observed. The magnetization hysteresis loop curves revealed that the high temperature heat-treated samples were paramagnetic, whereas the low-temperature heat-treated sample was a mixture of a small amount of ferro- or ferrimagnetic material with a majority being paramagnetic material. © 2003 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Gg Ferrimagnetics
79.20.Hx Electron impact: secondary emission
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Microwave permeability spectra of ferromagnetic thin films over a wide range of temperatures

M. Ledieu, F. Schoenstein, J.-H. Le Gallou, O. Valls, S. Queste, F. Duverger, and O. Acher

J. Appl. Phys. 93, 7202 (2003); http://dx.doi.org/10.1063/1.1555902 (3 pages) | Cited 13 times

Online Publication Date: 9 May 2003

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Ferromagnetic materials are of great interest today for high frequency applications in microelectronics (M-RAMs, planar inductors, etc.) or magnetic recording systems, taking advantage of the high levels of saturation magnetization of ferromagnetics. We are presenting a setup permitting permeability measurements from 10 MHz up to 6 GHz in the 77–400 K temperature range. An existing single-coil perturbation technique is modified to allow precise and accurate microwave measurements. An experimental validation of the technique is performed. Measurements on a CoFeSiB thin film are presented. The clear effect of the temperature on the whole permeability spectra is shown for soft ferromagnetic thin films, including CoNbZr. © 2003 American Institute of Physics.
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07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
06.20.F- Units and standards
75.50.Bb Fe and its alloys
75.50.Cc Other ferromagnetic metals and alloys
84.40.-x Radiowave and microwave (including millimeter wave) technology

Microstructure and magnetic properties of the FeTaCN nanocrystalline thin films

C. Y. Chou, P. C. Kuo, Y. D. Yao, S. C. Chen, A. C. Sun, and C. T. Lie

J. Appl. Phys. 93, 7205 (2003); http://dx.doi.org/10.1063/1.1555904 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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FeTaCN films were deposited on quartz substrates by cosputtering of Fe and TaC targets at room temperature with different N2 flow rate ratios in the sputtering gas. The as-deposited films were postannealed in vacuum for 30 min at various temperatures. The effects of annealing temperature on the N2 flow rate ratio and film thickness on the magnetic properties and microstructure of the film were investigated. X-ray diffraction and transmission electron microscopy analyses show that the as-deposited FeTaCN film has a nanocrystalline structure or mixing phases of nanocrystalline and amorphous. Nanocrystalline as-deposited film with good soft magnetic properties (in-plane coercivity Hc∥=1∼2 Oe and 4πMs=12–14 kG) can be obtained by controlling the N2 flow rate ratio and film thickness. The soft magnetic properties can be improved by postannealing the as-deposited film at 200–300 °C as the N2 flow rate ratio is higher than 5 vol %. For the Fe71.03Ta6.1C7.2N15.67 film, the Hc∥ value decreases as the film thickness is increased when the annealing temperature is lower than 400 °C. After annealing at 300 °C, its Hc∥ is about 3.57 Oe as the film thickness is 50 nm and Hc∥ will decrease to 0.18 Oe as the film thickness is increased to 1000 nm. © 2003 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Tt Fine-particle systems; nanocrystalline materials
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.Cc Kinetics of defect formation and annealing

Effect of stress applied on the magnetization profile of Fe–Si–B amorphous wire

V. Zhukova, A. Zhukov, J. M. Blanco, J. Gonzalez, C. Gómez-Polo, and M. Vázquez

J. Appl. Phys. 93, 7208 (2003); http://dx.doi.org/10.1063/1.1555905 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2003

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The effect of tensile stress, σ, on hysteresis loops and magnetization profiles of Fe77.5B15Si7.5 amorphous wires has been measured. Measurements performed by a short movable coil permit one to obtain the dependence of remanent magnetization, μ0Mr, on the position of this coil, L. Increasing applied stress in tensile stress is applied, the initially rectangular local hysteresis loop measured for L=4 cm (at l=8 cm) becomes inclined, but then recovers its rectangular shape for larger stress. The μ0Mr(σ) dependence shows an increase with σ for all L. The stress dependence of both μ0Mr and H∗ can be understood in terms of a competition between magnetostatic and magnetoelastic energy. © 2003 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.80.+q Magnetomechanical effects, magnetostriction

Magnetic properties of FeCuNbSiB nanocrystalline alloy powder cores using ball-milled powder

G. H. Kim, T. H. Noh, G. B. Choi, and K. Y. Kim

J. Appl. Phys. 93, 7211 (2003); http://dx.doi.org/10.1063/1.1555907 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2003

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Cold-pressed nanocrystalline powder cores were fabricated using powders of nanocrystalline ribbons which were ball milled for short time. Their magnetic properties at high frequency were measured. The powder size ranges from 20 to 850 μm and the contents of the glass binder are between 1 and 8 wt %. For cores composed of large particles of 300–850 μm with 5 wt % glass binder, we obtained a stable permeability of 100 up to 800 kHz, a maximum level 31 of quality factor at frequency of 50 kHz, and 320 mW/cm3 core loss at f=50 kHz and Bm=0.1 T. This is mainly due to the good soft magnetic properties of the powders and the higher insulation of powder cores which cause low eddy current losses. © 2003 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Bx Metals, semimetals, and alloys

Depth profiles of magnetostatic and dynamic characteristics in annealed Co66Fe4B15Si15 amorphous ribbons

Y. W. Rheem, C. G. Kim, B. S. Lee, L. Jin, C. O. Kim, E. E. Shalyguina, and E. A. Gan’shina

J. Appl. Phys. 93, 7214 (2003); http://dx.doi.org/10.1063/1.1540042 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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We investigated the magnetostatic and dynamic properties of annealed and etched Co66Fe4B15Si15 amorphous ribbons. The near-surface magnetic characteristics of the annealed samples showed the gradual growth of a hard magnetic layer with increasing annealing time; that is, coercivity Hc and saturation field Hs increase from 15 to 600 Oe and from 45 to 1500 Oe, respectively. On the etching effect on the magnetic property in an 8 h annealed sample, the hard magnetic layer near the sample surface was retained for the sample with etching time tetch<40 s, but the influence of the ribbon core on the near-surface magnetic properties of the sample was discovered for tetch⩾50 s. When the thickness of hard magnetic layer is about 1 μm, the asymmetric giant magnetoimpedance (GMI) profiles, the so-called GMI valve, do not show hysteresis. As the thickness is reduced, a hysteretic GMI is observed due to the cyclic change of magnetization in the hard magnetic layer under a cyclic field. © 2003 American Institute of Physics.
Show PACS
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.70.Rf Surface magnetism
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Gh Other heat and thermomechanical treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Vv High coercivity materials
75.47.De Giant magnetoresistance

Enhanced magnetic anisotropy in granular cobalt–copper alloys

B. R. Pujada, E. H. C. P. Sinnecker, A. M. Rossi, and A. P. Guimarães

J. Appl. Phys. 93, 7217 (2003); http://dx.doi.org/10.1063/1.1543860 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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We have used the X-band ferromagnetic resonance (FMR) spectra of granular Co5Cu95 ribbons, as cast, and heat treated as a function of temperature, in order to study their magnetic and structural properties. From a model derived for the temperature dependence of the FMR linewidth, the mean diameter and effective anisotropy constant (Keff) of the magnetic grains were obtained. Enhanced values of Keff in comparison to the bulk materials, and also a decrease with increasing mean diameter, have been found. Our results indicate a large influence of the surface magnetic anisotropy in the smaller grains and also on the behavior of the resonance field and linewidth. © 2003 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Gw Magnetic anisotropy
75.50.Cc Other ferromagnetic metals and alloys
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.70.Rf Surface magnetism
81.40.Gh Other heat and thermomechanical treatments

Magnetoelastic hysteresis of amorphous ribbons

L. Kraus and P. Švec

J. Appl. Phys. 93, 7220 (2003); http://dx.doi.org/10.1063/1.1540043 (3 pages)

Online Publication Date: 9 May 2003

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The influence of tensile stress on hysteresis loops and the magnetomechanical effect in high-magnetostrictive Fe-rich and low-magnetostrictive Co-rich amorphous ribbons were investigated. In the as-quenched Fe-rich alloy a very complex behavior is observed, which indicates the interplay of different types of magnetization processes. Uniaxial magnetic anisotropies, induced by stress annealing, eliminate the rotational processes in Fe-rich materials and the domain-wall motion in Co-rich materials. Thus, the role of the two different mechanisms in the magnetoelastic hysteresis can be studied separately. It is shown that irreversible domain-wall movements are responsible for the large hysteresis in the Fe-rich alloy, while the purely rotational magnetization process can account for the essentially anhysteretic behavior of the Co-rich alloy. The theoretical model by Livingston [J. D. Livingston, Phys. Status Solidi 70, 591 (1982)] can well explain the anhysteretic behavior. © 2003 American Institute of Physics.
Show PACS
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys
81.40.Rs Electrical and magnetic properties related to treatment conditions
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