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Title: He{sup +} ion irradiation study of continuous and patterned Co/Pd multilayers

Abstract

Ion irradiation of continuous and patterned (Co/Pd){sub n} magnetic multilayer films has been studied as a mean to control magnetic anisotropy as well as to evaluate possible ion irradiation damage involved in ion-beam proximity lithography patterning. The coercivity of patterned medium was found to decrease from 11 kOe for as patterned samples to 0.3 kOe for samples with 800 {mu}C/cm{sup 2} ion irradiation. Remnant squareness of the patterned samples remained essentially unchanged. As the number of bilayers increases in the sample, the effects vary, suggesting that several mechanisms of damage occur. Significantly, for typical irradiation doses used in ion-beam proximity lithography, no measurable alteration of magnetic properties was observed.

Authors:
; ; ; ; ;  [1];  [2];  [2];  [2]
  1. Center for Nanomagnetic Systems, University of Houston, Houston, Texas 77204 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20982826
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 8; Other Information: DOI: 10.1063/1.2719018; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANISOTROPY; COBALT; COERCIVE FORCE; FERROMAGNETIC MATERIALS; HELIUM IONS; HYSTERESIS; ION BEAMS; IRRADIATION; LAYERS; MAGNETIC PROPERTIES; PALLADIUM; RADIATION DOSES; THIN FILMS

Citation Formats

Parekh, Vishal, Smith, Darren, E, Chunsheng, Rantschler, James, Khizroev, Sakhrat, Litvinov, Dmitri, Electrical Engineering, University of California--Riverside, Riverside, California 92521, Center for Nanomagnetic Systems, University of Houston, Houston, Texas 77204, and Sentorix, Inc., Pearland, TX 77584. He{sup +} ion irradiation study of continuous and patterned Co/Pd multilayers. United States: N. p., 2007. Web. doi:10.1063/1.2719018.
Parekh, Vishal, Smith, Darren, E, Chunsheng, Rantschler, James, Khizroev, Sakhrat, Litvinov, Dmitri, Electrical Engineering, University of California--Riverside, Riverside, California 92521, Center for Nanomagnetic Systems, University of Houston, Houston, Texas 77204, & Sentorix, Inc., Pearland, TX 77584. He{sup +} ion irradiation study of continuous and patterned Co/Pd multilayers. United States. doi:10.1063/1.2719018.
Parekh, Vishal, Smith, Darren, E, Chunsheng, Rantschler, James, Khizroev, Sakhrat, Litvinov, Dmitri, Electrical Engineering, University of California--Riverside, Riverside, California 92521, Center for Nanomagnetic Systems, University of Houston, Houston, Texas 77204, and Sentorix, Inc., Pearland, TX 77584. Sun . "He{sup +} ion irradiation study of continuous and patterned Co/Pd multilayers". United States. doi:10.1063/1.2719018.
@article{osti_20982826,
title = {He{sup +} ion irradiation study of continuous and patterned Co/Pd multilayers},
author = {Parekh, Vishal and Smith, Darren and E, Chunsheng and Rantschler, James and Khizroev, Sakhrat and Litvinov, Dmitri and Electrical Engineering, University of California--Riverside, Riverside, California 92521 and Center for Nanomagnetic Systems, University of Houston, Houston, Texas 77204 and Sentorix, Inc., Pearland, TX 77584},
abstractNote = {Ion irradiation of continuous and patterned (Co/Pd){sub n} magnetic multilayer films has been studied as a mean to control magnetic anisotropy as well as to evaluate possible ion irradiation damage involved in ion-beam proximity lithography patterning. The coercivity of patterned medium was found to decrease from 11 kOe for as patterned samples to 0.3 kOe for samples with 800 {mu}C/cm{sup 2} ion irradiation. Remnant squareness of the patterned samples remained essentially unchanged. As the number of bilayers increases in the sample, the effects vary, suggesting that several mechanisms of damage occur. Significantly, for typical irradiation doses used in ion-beam proximity lithography, no measurable alteration of magnetic properties was observed.},
doi = {10.1063/1.2719018},
journal = {Journal of Applied Physics},
number = 8,
volume = 101,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • We studied the reversal properties of perpendicular anisotropy (Co/Pd) multilayers with different crystallographic textures. In case of continuous films, an increase in the coercivity and reduction in the switching field distribution (SFD) were observed as the growth is improved. From magnetic force microscopy, a stripe-type domain configuration was observed in films deposited at low gas pressure while a bubble-type domain was observed in high pressure deposited films. In patterned films, the SFD did not vary significantly for samples with different textures although a 2 kOe increase in the switching field was measured. In patterned structures, the controllability of SFD maymore » not be related to the improvement of film crystallographic growth as was observed for unpatterned films. The results from this study indicate that local variation in the intrinsic film properties plays a major role in the SFD.« less
  • The three-dimensional magnetic structure and reversal mechanism of patterned Co/Pt multilayers, were imaged using complementary Lorentz transmission electron microscopy (LTEM) (in-plane component) and magnetic transmission x-ray microscopy (M-TXM) (perpendicular magnetization). The Co/Pt films with perpendicular anisotropy were patterned by ion irradiation through a stencil mask to produce in-plane magnetization in the irradiated regions. The boundaries of the patterns, defined by the transition from out-of-plane to in-plane magnetization, were found to be determined by the stencil mask, whilst the scale of the magnetic reversal by the physical microstructure. The nucleation fields were substantially reduced to 50 Oe for the in-plane regionsmore » and 1 kOe for the perpendicular regions, comparing to 4.5 kOe for the as-grown film. The perpendicular reversals were found to always originate at the pattern boundaries.« less
  • The three-dimensional magnetic structure and reversal mechanism of patterned Co/Pt multilayers, were imaged using complementary Lorentz transmission electron microscopy (in-plane component) and magnetic transmission x-ray microscopy (perpendicular magnetization). The Co/Pt films with perpendicular anisotropy were patterned by ion irradiation through a stencil mask to produce in-plane magnetization in the irradiated regions. The boundaries of the patterns, defined by the transition from out-of-plane to in-plane magnetization, were found to be determined by the stencil mask. The nucleation fields were substantially reduced to 50 Oe for the in-plane regions and 1 kOe for the perpendicular regions, comparing to 4.5 kOe for themore » as-grown film. The perpendicular reversals were found to always originate at the pattern boundaries.« less
  • Cited by 6
  • Co/Pt multilayer films with perpendicular magnetic anisotropy and large out-of-plane coercivities of 3.9 - 8.5 kOe have been found to undergo a spin reorientation transition from out-of-plane to in-plane upon irradiation with 700 keV nitrogen ions. X-ray reflectivity experiments show that the multilayer structure gets progressively disrupted with increasing ion dose, providing direct evidence for local atomic displacements at the Co/Pt interfaces. This effectively destroys the magnetic interface anisotropy, which was varied by about a factor of two, between KS@ 0.4 erg/cm2 and KS@ 0.85 erg/cm2 for two particular films. The dose required to initiate spin-reorientation, 6x1014 N+/cm2 and 1.5x1015more » N+/cm2, respectively, scales with KS. It is roughly equal to the number of Co interface atoms per unit interface area contributing to KS.« less