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Imaging the equilibrium state and magnetization dynamics of partially built hard disk write heads

DOI: 10.1063/1.4922374 DOI Help

Authors: R. Valkass (University of Exeter) , W. Yu (University of Exeter) , L. Shelford (University of Exeter) , P. S. Keatley (University of Exeter) , T. H. J. Loughran (University of Exeter) , R. Hicken (University of Exeter) , S. Cavill (University of York, Diamond Light Source) , G. Van Der Laan (Diamond Light Source) , S. Dhesi (Diamond Light Source) , M. A. Bashir (Seagate Technology) , M. A. Gubbins (Seagate Technology) , P. J. Czoschke (Seagate Technology) , R. Lopusnik (Seagate Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Applied Physics Letters , VOL 106 (23)

State: Published (Approved)
Published: June 2015
Diamond Proposal Number(s): 9287

Open Access Open Access

Abstract: Four different designs of partially built hard disk write heads with a yoke comprising four repeats of NiFe (1nm)/CoFe (50nm) were studied by both x-ray photoemission electron microscopy (XPEEM) and time-resolved scanning Kerr microscopy (TRSKM). These techniques were used to investigate the static equilibrium domain configuration and the magnetodynamic response across the entire structure, respectively. Simulations and previous TRSKM studies have made proposals for the equilibrium domain configuration of similar structures, but no direct observation of the equilibrium state of the writers has yet been made. In this study, static XPEEM images of the equilibrium state of writer structures were acquired using x-ray magnetic circular dichroism as the contrast mechanism. These images suggest that the crystalline anisotropy dominates the equilibrium state domain configuration, but competition with shape anisotropy ultimately determines the stability of the equilibrium state. Dynamic TRSKM images were acquired from nominally identical devices. These images suggest that a longer confluence region may hinder flux conduction from the yoke into the pole tip: the shorter confluence region exhibits clear flux beaming along the symmetry axis, whereas the longer confluence region causes flux to conduct along one edge of the writer. The observed variations in dynamic response agree well with the differences in the equilibrium magnetization configuration visible in the XPEEM images, confirming that minor variations in the geometric design of the writer structure can have significant effects on the process of flux beaming.

Journal Keywords: Configuration; Copper; Electron Microscopy; Equilibrium; Images; Iron; Magnetic Circular Dichroism; Magnetic Disks; Magnetization; Nickel; Photoemission; X Radiation

Subject Areas: Physics, Engineering

Instruments: I06-Nanoscience