Direct measurement of single-dot coercivity and statistical analysis of switching field distribution in bit-patterned media using scanning hard-X-ray nanoprobe

Abstract

To investigate the possible sources of the switching field distribution in bit-patterned media, we applied a scanning hard-X-ray nanoprobe technique based on X-ray magnetic circular dichroism spectroscopy to an array of Co-Pt dots with the typical diameters of 200 nm. Element-specific magnetization curves at the Pt L3 edge were measured for individual dots isolated from each other, and the magnetization switching field (coercivity) values were determined for more than 100 individual dots. To assess the effect of dot diameters as a possible source of switching field distribution, a statistical analysis of the coercivity values and dot diameters measured for many dots was performed. The resulting switching field distribution had a mean of ⟨HSW⟩=1.80 kOe and a standard deviation of σHSW = 0.64 kOe. The relative deviation of σHSW/⟨HSW⟩=36% was not in good agreement with the relative dispersion in a dot diameter of σD/⟨D⟩=2.7%, and no clear correlation between the coercivity and dot diameter was observed. These results may suggest other possible sources of switching field distribution than dot diameter, such as dispersion in the c-axis orientation and in magnetocrystalline anisotropy.

Imaging of transient magnetization dynamics of Co/Pt multilayer dots with X-ray magnetic circular dichroism excited by microwaves

“…The shorter wavelength of X-rays allows one to focus onto a spot below 100 nm using Fresnel zone plate optics 5,9) or a Kirkpatrick-Baez (KB) mirror set-up. 15,16) The ability of focusing in the nanoscale enables one to probe nanostructures and perform spatially resolved measurements. [3][4][5][6][7][8][9][10][11][12] Another unique feature of XMCD measurement is its element selectivity by changing photon energy.…”