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The magnetic damping constant is a proportionality constant for energy dissipation upon the precession of the magnetic moment, and it characterizes magnetization dynamics. In this study, ferrimagnetic Gd3Fe5O12 (111) epitaxial films are grown using pulsed laser deposition, and the temperature dependence of the ferrimagnetic resonance and damping constant (αFiM) is investigated. The results reveal that αFiM is approximately an order of magnitude smaller than those of other ferrimagnetic metals reported to date. Our results emphasize the potential of Gd3Fe5O12 films in ultralow-power spintronic applications. [ABSTRACT FROM AUTHOR]

Ultrathin Al[O.sub.x] layers 5-25 [Angstrom] thick were deposited using the atomic-layer chemical vapor deposition technique. A magnetic thickness loss of ~1 [Angstrom] has been estimated at CoFe-A1[O.sub.x] or NiFe-A1ONiFe-Al[O.sub.x] interfaces. The two-dimensional integrity of the thin Al[O.sub.x] films at thickness >7 [Angstrom] has been validated by the differential switching of two magnetic layers sandwiching a ultrathin Al[O.sub.x] layer and the distinct cross-sectional transmission-electron-microscopy images. No appreciable tunnel magnetoresistance effect has been measured from the fabricated magnetic tunnel junction devices. A proper in situ treatment prior to and/or after Al[O.sub.x] deposition and a proper protection of the underlying magnetic layer are expected for further improvements. Index Terms--Atomic-layer chemical vapor deposition (ALCVD), A1[O.sub.x], decoupling, J-V, magnetic thickness loss, magnetic tunnel junction (MTJ), thin films, tunnel magnetoresistance, tunnel barrier.

Research into the response of the free layer with a parallel hard bias has involved simulating tunneling magnetoresistance films and devices. It was found that the tunneling magnetoresistance film has hysteresis in the response of the free layer largely because of the multigrain properties of the parallel magnet.

Research into the impact of a dc stress voltage on the junction resistance and magnetoresistance of spin-dependent tunneling junctions with naturally oxidized barriers is presented. It was established that there is a threshold voltage, which rises with barrier thickness, at which junction resistance begins to fall irreversibly.

The study revealed the fundamentally important result that is the flop mechanism of the synthetic antiferromagnetic layer (SAF) occurs when a magnetic field is greater than a critical field strength. It experimentally concluded that the exchange bias directions are determined by the magnetization of the ferromagnetic films, and not by the applied magnetic field during annealing.

The face-centered-tetragonal (fct) antiferromagnetic phase is a necessary condition for exchange biasing the thickness of the antiferromagnetic layer, which determines the magnitude and the thermal stability of exchange biasing in exchange biased F/AF systems. The blocking temperature solely depends on the quality of the antiferromagnetic phase since thinning of the antiferromagnetic layer thickness does not affect the local blocking temperature distribution.

Spin valve films with synthetic antiferromagnetic CoFe/Ru/CoFe/IrMn were developed. Synthetic spin valve films were found to have large giant magnetoresistance ratio and large effective exchange field and excellent thermal stability. Spin valve readers showed high amplitude, large dynamic range and excellent magnetic stability which indicated their extendibility for ultrahigh density read head applications.

We have successfully demonstrated longitudinal recording at areal densities greater than 60 Gb/[in.sup.2] at data rates as high as 160 Mbps (20 MB/s) and at a Bit-Aspect-Ratio (BAR) of 5.7, using merged inductive-write/spin-valve-read heads with microactuators on low noise thin film disks. The heads were fabricated with the standard photolithography and wafer pole trimming used in currently available commercial products. At track densities of 60 KTPI and higher, traditional serving mechanism will not be adequate. With the use of a microactuator, we can further improve the track density by 15%, the linear density by 10% and the areal density by more than 20%. Thus, using microactuator with the 50 Gb/[in.sup.2] head/media combination we have increased our areal density achievement up to 63.2 Gb/[in.sup.2]. Index Terms--Magnetic devices, magnetic disk recording, magnetic films, magnetic heads.

We investigated the effect of aluminum thickness on RA (resistance [multiplied by] area product) and MR ratio in spin-dependent tunnel junctions. Very low RA values below 40 [Omega]/[[micro]m.sup.2] and a maximum MR ratio of 6% were obtained in [Ni.sub.81][Fe.sub.19]/[Al.sub.2][O.sub.3]/[Ni.sub.81][Fe.sub.19] tunneling junctions fabricated using natural oxidation of aluminum. The MR ratio significantly increased with use of [Co.sub.90][Fe.sub.10] electrodes. Using natural oxidation of 6 [Angstrom] aluminum, RA and MR ratio of these junctions are ~50 [Omega][[micro]m.sup.2] and ~28%, respectively. The MR ratio and the junction resistance strongly depend on the aluminum thickness. The optimum thickness of aluminum is 6-7 [Angstrom] for natural oxidation. Index Terms--Giant magnetoresistance, magnetic films and devices, magnetic materials for heads, magnetic spin tunneling.

We have successfully demonstrated recording at areal densities as high as 36 Gb/[in.sup.2] at data rates as high as 173 Mbits/s (21.6 MB/s) and at a Bit-Aspect-Ratio (BAR) of 7.3, using merged inductive-write/spin-valve-read heads on low noise thin film disks. Recording at a data rate of 590 Mbits/s (73.8 MB/s) has also been achieved at the corresponding linear density of 231 KBPI. Comparisons with previous areal density demonstrations have also been summarized.

IrMn exchange biased bottom spin-valve films of structure Ta/underlayer/ IrMn/CoFe/Cu/CoFe/NiFe/Ta were prepared using ion beam deposition techniques. The exchange bias field exhibits strong underlayer thickness dependence. For the first time, a large exchange energy of 0.29 erg/[cm.sup.2] was measured in spin-valve films exchange biased by a disordered antiferromagnet, comparable to the values usually obtained in spin-valve films exchange biased by an ordered antiferromagnet. We have conducted a comparative study on both bottom and top exchange biased spin-valve and ferromagnetic/antiferromagnetic bilayer films. The results indicate that the exchange field obeys very well the inverse pinned layer thickness law over a thickness range from 200 [Angstrom] down to 10 [Angstrom]. The exchange energy for bottom spin-valve films is, however, a factor of two larger than that for top spin-valve films. When normalized, the exchange field exhibits the same temperature dependence for both bottom and top spin-valve films. The enhancement in exchange biasing is mainly attributed to an enhanced texture for fcc (111) crystallographic orientation of the IrMn layer in bottom spin-valve films. Index terms-exchange bias, ion beam deposition, bottom spin-valve, underlayer, IrMn

We have designed and fabricated dual spin valve heads with synthetically pinned layers. They have excellent sensitivity. The read-back waveform has a small asymmetry and that is also insensitive to the bias current. The read gap length is of 0.14 [micro] m and the write gap length is of 0.2 [micro] m. The read heads have a nominal magnetic trackwidth of 0.5 [micro] m and a nominal write magnetic trackwidth of 0.8 [micro] m. The write heads were conventional inductive heads with their pole geometry defined by focused ion beam (FIB) technology. The dual spin valve heads have achieved an areal read/write density as high as 14.5 Gb/[in.sub.2] at a data transfer rate of 23~24 MB/sec. The sensitivity of the readers is as high as 3.6 mVp-p/[micro] m. The bit aspect ratio is as high as 14. Index Terms--Dual spin valve head, GMR reader design concept, GMR head thermal stability, synthetic antiferromagnetic-pinned layers.

Two sets of PtPdMn exchange biased films Ta 50 Å/CoFe 100 Å/PtPdMn (t[sub AF]) Å/Ta 50 Å, with PtPdMn thickness, t[sub AF]=350, 600 Å, were deposited on Si substrates by dc magnetron sputtering techniques. After magnetic annealing, these two sets of films exhibited values of exchange bias field, H[sub ex]=229 and 254 Oe, respectively. The PtPdMn layer was then thinned to various thicknesses from 600 down to 50 Å by ion beam etching. H[sub ex] does not retain its original value. It decreases with decreasing t[sub AF] and becomes zero at t[sub AF]∼75 Å. In addition, we have observed that the training effect or the anomalous hysteresis loss becomes more pronounced with decreasing t[sub AF]. This confirms that not only face-centered-tetragonal phase but, more critically, t[sub AF] plays role in determining exchange biasing and its thermal stability. The blocking temperature, T[sub B], appears unaffected by the thinning of the PtPdMn layer, and no apparent change occurs in the local blocking temperature distribution, as suggested by the finite size effect. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The spin flop of synthetic antiferromagnetic pinned layers (SAF), under a magnetic field has been theoretically predicted and recently reported [J. G. Zhu and Y. Zheng, IEEE Trans. Magn. 34, 1063 (1998); J. G. Zhu, IEEE Trans. Magn. 35, 655 (1999)]. However, no experimental data have yet being reported to confirm the theoretical prediction. This article will provide direct experimental evidence to confirm the spin flop phenomenon in SAF layers. A spin valve, [CoFe/NiFe]/Cu/[CoFe(II)/Ru/CoFe(I)]/IrMn, was used to verify the spin flop in SAF layers. The exchange bias direction of CoFe(I)/IrMn was introduced by a magnetic annealing process at 225 °C with a field strength of H[sub an](10 kOe) and the exchange bias direction was found parallel to the magnetic field. These samples serve as the reference for the remaining experiments. By magnetic annealing the reference samples at 225 °C with lower magnetic fields, we found that the magnetic field threshold for SAF spin flop is about 1 kOe. When the field is further increased, the spins of CoFe(I) and CoFe(II) scissor toward the applied magnetic field axis and the moment of the SAF reaches saturation when the applied field is equal to or greater than 10 kOe. Thus the above experiments demonstrate the flop behavior of the SAF. It also provides direct evidence that the exchange bias direction between a ferro/antiferromagnetic interface is determined by the magnetization of the ferromagnetic layer, not by the magnetic annealing field. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this article, we report the magnetic properties of ultrathin (15–200 Å) NiFe and CoFe films deposited using ion beam deposition techniques. They are symmetrically sandwiched between Ta, Cu, or Ta/Cu under and capping layers. NiFe and CoFe films grown between Ta/Cu and Cu/Ta bilayers exhibit the smallest magnetic thickness loss of about 1 Å. This interfacial magnetic dead layer thickness, t[sub 0], is about 5 Å for Cu-sandwiched films and about 15 Å for Ta-sandwiched films. As the film thickness becomes thinner than 100 Å, the magnetic properties are found to be more sensitive to the choice of material and growth environment. CoFe films show an interfacial contribution, λ[sub i], about ten times larger than that for NiFe films. Among others, NiFe and CoFe films sandwiched by Ta/Cu and Cu/Ta bilayers exhibit the smallest values of λ[sub i]. The magnetic anisotropy in Ta-sandwiched CoFe films appears to be predominantly magnetoelastic in nature. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]