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We experimentally demonstrate single pulse toggle switching of the magnetization of GdFeCo disks with perpendicular to film plane anisotropy, which diameter ranges from 3 μm to 400 nm using 35 fs linearly polarized laser pulses. Two different magnetic states can be observed depending on the laser fluence: either a deterministic switching of the disk magnetization or a randomly oriented disk. We report that the fluence required to observe both magnetic states show a non-monotonic behavior with disk diameter and that the smallest disks require the lowest minimum fluence for achieving single pulse all-optical helicity-independent switching. Different evolution of the fluence thresholds for both phenomenon as a function of the disk size is observed and discussed. [ABSTRACT FROM AUTHOR]

We introduce a theoretical and experimental framework that enables quantitative measurements of the temperature and magnetic field profiles governing the thermo-magnetic write process in heat assisted magnetic recording. Since our approach allows the identification of the correct temperature dependence of the magneto-crystalline anisotropy field in the vicinity of the Curie point as well, it provides an unprecedented experimental foundation to assess our understanding of heat assisted magnetic recording. [ABSTRACT FROM AUTHOR]

The effect of holmium (Ho) doping in films of Ni0.8Fe0.2 (NiFe) is investigated. The ferromagnetic resonance (FMR) is measured, and the linewidths (Δf) are fit to a model that incorporates broadening from inhomogeneities and intrinsic damping (αLLG). The data reveal a drastic increase in Δf for increasing Ho concentration in the NiFe films, while the fits of this data to the model indicate this is largely due to an increase in αLLG. At Ho concentrations of 10% and greater, the saturation magnetization is reduced by more than 60% while the FMR is no longer observable, which is likely due to the signal falling below the noise floor from further linewidth broadening and decreased magnetization. In general, the saturation magnetization decreases continuously with Ho concentration, presumably due to local ferrimagnetic order induced by the Ho moments. However, the coercivity is essentially unchanged by the doping, while the magnetic anisotropy HK is unchanged out to 2% Ho, beyond which there is an abrupt step-function-like increase. The data suggest Ho concentrations as small as 2% can substantially increase intrinsic damping in NiFe while minimizing change in other practical magnetic properties. [ABSTRACT FROM AUTHOR]

Micromagnetic simulations have been performed to investigate the write position shifts in heat-assisted magnetic recording (HAMR) under variation of variables including the thermal profile, write field magnitude, head velocity, media damping, and write field rise time. Simulations reveal that a larger head velocity or a larger media damping tends to shift the write positions towards the heat center. Simulation results are also compared to the predictions of an analytical model based on classical mean-field theory. It is found that, with smaller thermal gradients the analytical model tends to give write positions closer to the heat center; whereas when thermal gradients are larger it tends to shift the write positions away from the heat center. All these effects appear to be dynamic, and can be understood by recognizing the lag between spin temperature and lattice temperature that cannot be captured by the analytical model that assumes equilibrium at all times. [ABSTRACT FROM AUTHOR]

In order to achieve higher areal density, magnetization transition width must be reduced. This requires small media switching field distribution (SFD). Here we explore SFD and transition width in heat assisted magnetic recording and microwave assisted magnetic recording. We reveal that for energy assisted magnetic recording, additional SFD broadening exists as compare to conventional perpendicular recording. We show the effect of SFD broadening on transition width and the implications to the magnetic recording system as the areal density increases. [ABSTRACT FROM AUTHOR]

A local ferromagnetic resonance (FMR) technique using a thin-film microwave probe fabricated on coaxial transmission line is presented. Some key features of this probe are its micron-scale size coupled with broadband FMR characterization and mobility: a small area of any location on a magnetic medium can be probed. Permeability of Permalloy (Py) films has been measured, where the authors extract physical parameters, such as FMR frequency, anisotropy field, damping, and spin wave exchange constant, in excellent agreement with independent measurements. Samples of arbitrary shape and size can be measured with a spatial resolution that scales with the size of the probe “tip.” [ABSTRACT FROM AUTHOR]