H. Ouahmane

Frequency‐dependent complex permeability in rare earth‐substituted cobalt/nonmagnetic transition metal soft ferromagnetic amorphous thin films

Using radio frequency (rf) sputtering, we have prepared in presence of a static magnetic field, ferromagnetic thin films of composition (Co93Zr7)100−yREy(RE=Nd,Pr,Dy,Tb... a magnetic rare earth element). This study was performed for small amounts of RE substitution (0<y<3). These films exhibit attractive soft magnetic properties similar to CoZr alloys: low coercivity (Hc∼1 Oe), and a high saturation induction (4πMs≳10 kG). A low in‐plane uniaxial anisotropy Hk was induced, whose magnitude depends upon the composition and the preparation parameters. Substitution by RE atoms affects essentially the μ frequency‐response. Depending on the nature, the concentration of RE atoms and on the value of Hk, a high relative rotational permeability μ (μ’∼500–3000 at frequencies up to 500 MHz) was obtained. Also depending on RE and on y, high μ‘ (μ‘∼400–3000 at ν∼1 GHz) distributed over a very broad frequency range (Δν∼500–2500 MHz) could be measured.

Variations of the local anisotropy versus Tb content in amorphous CoZrTb thin films

The magnetic properties of rf sputtered amorphous (Co93Zr7)100−xTbx thin films were investigated as a function of Tb content for 0≤x≤2 by transverse biased initial susceptibility measurements. The deposition was performed in a magnetic field. This films exhibit a very well‐defined in‐plane anisotropy with negligible long‐range fluctuations and a small coercive field Hc, in accordance with the experimental data. The overall variations of the transverse susceptibility are related to the ripple, and the variations of the structure factor S with composition was measured. The local anisotropy Kloc, deduced from S, increases with the increasing amount of Tb in the layers. The results are discussed in terms of the single‐ion anisotropy of the rare earth.

Static and dynamic magnetic properties of (CoZr)100−x(RE)x amorphous thin films

The saturation magnetization, uniaxial anisotropy, and the dynamical magnetic properties of amorphous (Co92Zr8)100−x(RE)x thin films have been studied for various magnetic rare earths and for 0≤x≤3. The films were rf sputtered in presence of a dc magnetic field applied parallel to the film plane. For RE=Nd, Pr, Dy, and Tb, the films exhibit an in‐plane uniaxial anisotropy Ku, the magnitude of Ku being related to the particular RE. When RE=Gd and Sm a biaxial anisotropy develops constituted by a Ku and a perpendicular anisotropy Kp. The resonance linewidth as a function of x and RE is also reported.

A study of complex permeability in rare earth‐substituted cobalt/nonmagnetic transition metal amorphous thin films

By using radio‐frequency (rf) sputtering, amorphous ferromagnetic thin films of composition (Co93Zr7)100−yREy (RE=Nd, Pr, Dy, Tb, Gd, or Sm: magnetic rare earth elements) have been prepared. This work was performed for small amounts of RE substitution (y<3). These films exhibit static soft magnetic properties similar to CoZr alloys. For all compositions studied, a low in‐plane uniaxial anisotropy Hk appears, whose magnitude depends upon composition and preparation parameters. Above a critical substitution level, a biaxial anisotropy exhibiting an in‐plane Hk and a perpendicular component Hp is measured for films containing Gd or Sm. The substitution by RE atoms essentially affects the frequency‐response shape of complex permeability, depending on nature, concentration of RE atoms and on values of both Hk and Hp. High‐frequency permeability spectra could be well fitted by a theoretical model based on magnetization changes due to rotation, using a composition‐dependent Landau–Lifshitz damping term. The resu...

On the origin of the perpendicular anisotropy in rare earth-transition metal amorphous films

Abstract The induced anisotropy in amorphous (Co93Zr7)100−x(RE)x films has been studied. The sputter deposition was performed in a magnetic field. For RE = Nd, Pr, Dy and Tb, the formation of a well-defined in-plane uniaxial anisotropy Ku is related to the single-ion anisotropy of RE atoms. When RE = Gd and Sm, a biaxial anisotropy develops, comprising Ku and a perpendicular anisotropy Kp. This magnetic structure is expected to be related to the simultaneous formation of two distinct local structural configurations when the deposition temperature is higher than the critical value.

The role of local anisotropy in the origin of in-plane uniaxial anisotropy in amorphous CoZrNd thin films

The magnetic properties of rf-sputtered amorphous (Co93Zr7)100−xNdx thin films with 0 < x < 3.5 were investigated by transverse biased initial susceptibility (TBIS) measurements at both film/air and glass/film interfaces. The films exhibit a very well defined in-plane uniaxial anisotropy with negligible long-range fluctuations. A clear relationship could be established between Ku and Kloc, data which is discussed in terms of the single-ion anisotropy of the Nd ions. Although the value of Hk is the same at both interfaces, the as-determined ripple constants were found to be slightly different. This last result is believed to be related to some local defect, the origin of which is also advanced.

Induced, local anisotropy and anisotropy dispersion in amorphous Co-Zr-rare earth thin films

The authors point out that when prepared under adequate conditions, RF sputtered amorphous (Co/sub 0.93/Zr/sub 0.07/)/sub 100-x/ Tb/sub x/ thin films are obtained with fairly uniform magnetic properties and K/sub u/. These layers are suitable for an investigation of the overall effect of the random local anisotropy K/sub loc/ upon the micromagnetic properties of the films. The experimental data were obtained by transverse biased initial susceptibility and ferromagnetic resonance measurements. The value of K/sub loc/ was determined using the ripple theory. K/sub loc/ increases with increasing amount of Tb in the layers, which can be explained by the single-ion anisotropy mechanism. >

Coercive field of amorphous soft ferromagnetic films: dependence upon thickness

Abstract The thickness dependence of the coercive field Hc was examined in amorphous soft ferromagnetic films of various compositions. Hc increases with decreasing thickness, the highest rate being for Co92Zr7Tb1 films. This result is explained by the fact that this compound exhibits the largest random local anisotropy.

On the localized resonance mode in amorphous thin films: experimental observations

Abstract The overall properties of a new type of resonance mode specific to amorphous thin films are reported. This resonance mode was observed at 9.8 GHz — apart from the uniform mode — on a-Co 93− x Zr 7 (RE) x thin films where RE = Nd, Pr, Tb or Dy and for low RE content i.e. 0 x ≤ 4. The films exhibit a well defined in-plane uniaxial anisotropy field. For perpendicular orientation a single new resonance mode is observed with a resonance field H r ⪡ 4 πM s , while for parallel orientation a series of irregularly spaced modes are detected for fairly high applied fields. It is proposed that it could correspond to localized resonance related to the highly anisotropic local sites.

Characterization of local anisotropy and anisotropy dispersion of amorphous CoZrRE with rare earth REPr and Nd

Abstract The magnetic properties of rf sputtered amorphous (Co 93 Zr 7 ) 100− x (RE) x thin films were investigated where REPr and Nd and for a content of 0 x K u and K loc . The data are discussed in terms of single-ion anisotropy of the RE.