F.W.A. Dirne

Soft‐magnetic properties and structure of Fe/CoNbZr multilayers

The magnetic and structural properties of ion beam sputtered Fe/CoNbZr multilayers were studied as a function of the CoNbZr and Fe layer thickness. Good soft‐magnetic properties (coercivity 1000) are obtained only when the Fe grains are small, which is the case for multilayers with Fe layer thicknesses below 10 nm and CoNbZr layer thicknesses above 4 nm. Thick CoNbZr layers (>4 nm) are amorphous and repeated nucleation of Fe grains is observed. When the CoNbZr layers are too thin (<3 nm) they are crystalline and do not interrupt the Fe grain growth. The resulting columnar growth of Fe throughout the total film thickness leads then to a drastic decrease of permeability and increase of coercivity.

Induced anisotropy of amorphous CoFeSiB and CoNbZr magnetic materials

Uniaxial anisotropy induced by magnetic annealing was studied on amorphous CoFeSiB and CoNbZr layers. The kinetics of inducing the anisotropy is slowed down by a preanneal at 400°C. This effect is much stronger for CoNbZr than for CoFeSiB. An addition of 2% transition metal (TM) atoms does not influence the kinetics after preannealing appreciably. Simultaneously with inducing anisotropy magnetic annealing changes the magnetostriction. Two effects determine the anisotropy, orientation of pairs of different magnetic atoms and a contribution which also occurs in alloys with a single magnetic atom. The latter contribution is independent of type and size of the non-magnetic atom(s) and is attributed to Co - clusters.

Structural and soft-magnetic properties of Fe/CoNbZr and Fe/FeCrB multilayers

The magnetic and structural properties of ion‐beam‐sputtered Fe/FeCrB and Fe/CoNbZr multilayers were studied as a function of the FeCrB and CoNbZr layer thicknesses. Good soft‐magnetic properties (coercivity 1000) are obtained only when Fe grains are small, which requires, on the one hand, multilayers with Fe layer thicknesses below 10 nm and, on the other hand, FeCrB interlayers with thicknesses above 1 nm or CoNbZr interlayers with thicknesses above 3 nm. In this case interlayers are amorphous, which induces repeated nucleation of Fe grains. Only at FeCrB thicknesses of 1 nm are the interlayers crystalline due to interface mixing. This in contrast to CoNbZr interlayers which in addition grow epitaxially in a crystalline structure up to thicknesses of 3 nm. When interlayers are crystalline columnar growth of Fe results. As a consequence coercivity increases and permeability decreases.

Rapid thermal annealing of amorphous and nanocrystalline soft‐magnetic alloys in a static magnetic field

In this paper, we report on rapid thermal annealing (RTA) of two different soft‐magnetic materials in a static magnetic field: amorphous Co‐Nb‐Zr and nanocrystalline Fe‐Nb‐N. RTA of Co‐Nb‐Zr films was investigated in an attempt to suppress the crystallization of Co during the induction of the anisotropy, thus extending the process window of this material in video‐head manufacturing. Also, RTA of Fe‐Nb‐N was studied in an effort to promote the nucleation of nanocrystalline Fe grains, while suppressing the grain growth of α‐Fe. Using RTA in a magnetic field, Co‐Nb‐Zr alloys can be heated to temperatures above 525 °C, while suppressing the crystallization of hexagonal‐close‐packed Co. This temperature is considerably higher than that of conventional magnetic annealing in a furnace (400 °C), and thus allows us to combine annealing with other high‐temperature processes during recording head manufacturing procedures, such as glass bonding in sandwich head manufacturing. Furthermore, RTA allows the formation of ...

Magnetic and structural properties of iron/amorphous iron alloy multilayers

The magnetic and structural properties of ion‐beam and rf sputtered Fe/amorphous FeCrB multilayers were studied as a function of Fe and FeCrB layer thicknesses. The material is magnetically soft [μ (10 MHz)≊2000, Hc<100 A/m] and has a saturation magnetization ≊1.8 T if the FeCrB layer thickness is larger than 1 nm and the Fe thickness substantially lower than the domain wall thickness in Fe, 55 nm. The magnetostriction is dependent on the ratio of Fe and FeCrB layer thicknesses. Magnetostriction close to zero can be achieved, even after annealing to 350 °C. Domain patterns show the presence of a weak magnetic anisotropy.

Soft-magnetic multilayers for video recording heads

The effect of inducing a uniaxial anisotropy in microcrystalline Fe/FeCrB multilayers by applying a magnetic field during deposition was studied. Not only a reduction of remanent magnetization, but also an increase of permeability (at 10 MHz) are the result. In the hard axis direction a permeability of 6000 is found for a 10 nm/3 nm Fe/FeCrB multilayer. Calculations show that such high permeabilities are interesting for high-density recording heads without ferrite in the core. The domain structure in the head shows the presence of the uniaxial anisotropy. Large unwanted closure domains, in which rotation permeability is low, are present. >

Soft magnetic multilayers : the role of the magnetostriction

Abstract Interface mixing in ion beam sputtered Fe/CoNbZr and Fe/Co multilayers was studied by means of magnetostriction measurements. With decreasing period of modulation the magnetostriction of the multilayer increases. This effect is attributed to the presence of Fe-Co interdiffusion layers, which are formed by the interface mixing induced by Ar bombardment or by diffusion induced by annealing.

Spin-wave resonance in Fe-amorphous FeCrB multilayered structures

Abstract Fe/amorphous FeCrB multilayers were studied by ferromagnetic resonance measurements as a function of the interlayer thickness. The experimental determined value of (4Π M ) eff was compared with that computed from a model corresponding to a layered structure, built up of perfectly homogeneous and strongly coupled interlayers. The agreement is satisfactory except for too thin FeCrB or very thick Fe layer thickness, a result explained by the crystalline structure of the Fe interlayers. Generally in perpendicular resonance a well defined standing spin wave spectrum is detected from which the value of A eff was extracted. Some anomalies of the spectra are also presented.

Soft magnetic properties of Fe/FeN multilayer films prepared by reactive diode rf sputtering

Abstract Fe/FeN multilayer films with Fe and FeN layer thicknesses in the range of respectively 80–110 and 30–80 A have been prepared using a reactive diode rf sputtering system. Their crystallographic characteristics and magnetic properties have been investigated to determine the deposition conditions leading to good soft magnetic properties. Results show that the application of a static magnetic field during the deposition improves the soft magnetic propertoes of the films, by varying the mean iron grain orientation. Coercivity smaller than 40 A/m, saturation magnetization up to 1.9 T and permeability up to 1600 were obtained for a nitrogen partial pressure equal to 2 mTorr and the FeN layer thickness less than 50 A.

Study by ferromagnetic resonance of Fe/CoNbZr multilayer structures

Abstract The magnetic properties of Fe/CoZrNb multilayers were studied by ferromagnetic resonance as a function of CoZrNb interlayer thickness t c . For t c ⩾40 A the CoZrNb remains amorphous, a fairly good agreement exists between the as computed and experimental value of (4π M s ) eff and the resonance linewidth δ H is independent of t c . For t c ⩽30 A the experimental (4π M s ) eff deviates from the computed value, and δ H increases progressively when t c becomes smaller. These results correlate with structural properties which shown that thin CoZrNb interlayers are crystalline and Fe exhibits a columnar growth in the film thickness direction.