Thin Magnetic Disks Research Articles

Non-linear radial spinwave modes in thin magnetic disks

We present an experimental investigation of radial spin-wave modes in magnetic nano-disks with a vortex ground state. The spin-wave amplitude was measured using a frequency-resolved magneto-optical spectrum analyzer, allowing for high-resolution resonance curves to be recorded. It was found that with increasing excitation amplitude up to about 10 mT, the lowest-order mode behaves strongly non-linearly as the mode frequency redshifts and the resonance peak strongly deforms. This behavior was quantitatively reproduced by micromagnetic simulations. Micromagnetic simulations showed that at higher excitation amplitudes, the spinwaves are transformed into a soliton by self-focusing, and collapse onto the vortex core, dispersing the energy in short-wavelength spinwaves. Additionally, this process can lead to switching of the vortex polarization through the injection of a Bloch point.

The Hall resistivity of a two-dimensional electron gas in the presence of magnetic clusters with perpendicular magnetization

The Hall and longitudinal resistivity of a two-dimensional electron gas (2DEG) situated a small distance from a random distribution of identical perpendicular magnetized ferromagnetic clusters is studied. The magnetic clusters are modelled by thin magnetic disks. The electrons in the 2DEG are scattered by the magnetic field profiles as created by the magnetic clusters. Although the average magnetic field is zero, we find a nonzero Hall resistivity, which increases with k F , for small Fermi energies, but which tends to zero for higher energies. We find resonances in both the Hall and the longitudinal resistivity as function of the Fermi wave vector, which can be assigned to quasi-bound states under the disks.

Material and tribological properties of a-C:H film by plasma CVD for a disk overcoat

Amorphous hydrogenated carbon (a-C:H) film deposited by plasma chemical vapor deposition (PCVD) using toluene as a monomer is durable enough for a very thin magnetic disk overcoat. In this paper, we discuss the effect of deposition conditions on material and mechanical properties of this film. Lowering deposition gas pressure increases the amount of sp/sup 3/ bonded carbon and the hardness, and decreases the hydrogen content of the film. Increasing bias voltage leads to the same effects. Properties of a PCVD film could be well controlled by the hydrogen content besides the amount of sp/sup 3/ bonded carbon. PCVD films were more durable than sputtered a-C:H films of less than 10 nm thickness. A PCVD film enables us to reduce disk overcoat thickness.

Lubricant bonding via terminal bond network

Lubricants having a functional end group were bonded onto thin magnetic disks via electrostatic interaction or strong coordinate bond. A pseudo two-dimensional hydrogen-bond network was formed by two different lubricants, R/sup 1/NH/sub 2/ and R/sup 2/C00H, and gave contact angles of around 100 degrees over a wide range of NH/sub 2//COOH ratio. On the other hand, self-assembled monolayers of alkanethiols, which coordinate strongly to gold surfaces through the sulfur atom, also gave a hydrophobic surface: contact angles of ca. 105 degrees. FTIR spectra revealed that the alkyl chains in the terminally functionalized films were orientated perpendicular to the surface, which indicates the alkyl chains were densely packed in the resulting films. These methods are simple yet effective ways to produce lubricant layers of comb type structure.