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Title: Analytical TEM Examinations of CoPt-TiO2 Perpendicular Magnetic Recording Media

Abstract

For this analytical TEM study, nonmagnetic oxygen-rich boundaries were introduced into Co-Ptalloy perpendicular recording media by cosputtering Co and Pt with TiO2. Increasing the TiO2 content resulted in changes to the microstructure and elemental distribution within grains and boundaries in these films. EFTEM imaging was used to generate composition maps spanning many tens of grains, thereby giving an overall depiction of the changes in elemental distribution occurring with increasing TiO2 content. Comparing EFTEM with spectrum-imaging maps created by high-resolution STEM with EDXS and EELS enabled both corroboration of EFTEM results and quantification of the chemical composition within individual grain boundary areas. The difficulty of interpreting data from EDXS for these extremely thin films is discussed. Increasing the TiO2 content of the media was found to create more uniformly wide Ti- and O-rich grain boundaries as well as Ti- and O-rich regions within grains.

Authors:
 [1];  [2];  [3];  [2];  [2];  [1]
  1. Stanford University
  2. Seagate Media Research Center, Fremont
  3. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Shared Research Equipment Collaborative Research Center
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931895
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Microscopy and Microanalysis; Journal Volume: 13; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COBALT ALLOYS; PLATINUM ALLOYS; SUBSTRATES; TITANIUM OXIDES; MAGNETIC STORAGE DEVICES; CHEMICAL COMPOSITION; MICROSTRUCTURE; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY; GRAIN BOUNDARIES; TEM; EFTEM; Co; Pt; TiO2; perpendicular magnetic recording media; EDXS; EELS

Citation Formats

Risner, Juliet D., Nolan, T. P., Bentley, James, Girt, E, HarknessIV, S. D., and Sinclair, Prof. Robert. Analytical TEM Examinations of CoPt-TiO2 Perpendicular Magnetic Recording Media. United States: N. p., 2007. Web. doi:10.1017/S1431927607070213.
Risner, Juliet D., Nolan, T. P., Bentley, James, Girt, E, HarknessIV, S. D., & Sinclair, Prof. Robert. Analytical TEM Examinations of CoPt-TiO2 Perpendicular Magnetic Recording Media. United States. doi:10.1017/S1431927607070213.
Risner, Juliet D., Nolan, T. P., Bentley, James, Girt, E, HarknessIV, S. D., and Sinclair, Prof. Robert. Mon . "Analytical TEM Examinations of CoPt-TiO2 Perpendicular Magnetic Recording Media". United States. doi:10.1017/S1431927607070213.
@article{osti_931895,
title = {Analytical TEM Examinations of CoPt-TiO2 Perpendicular Magnetic Recording Media},
author = {Risner, Juliet D. and Nolan, T. P. and Bentley, James and Girt, E and HarknessIV, S. D. and Sinclair, Prof. Robert},
abstractNote = {For this analytical TEM study, nonmagnetic oxygen-rich boundaries were introduced into Co-Ptalloy perpendicular recording media by cosputtering Co and Pt with TiO2. Increasing the TiO2 content resulted in changes to the microstructure and elemental distribution within grains and boundaries in these films. EFTEM imaging was used to generate composition maps spanning many tens of grains, thereby giving an overall depiction of the changes in elemental distribution occurring with increasing TiO2 content. Comparing EFTEM with spectrum-imaging maps created by high-resolution STEM with EDXS and EELS enabled both corroboration of EFTEM results and quantification of the chemical composition within individual grain boundary areas. The difficulty of interpreting data from EDXS for these extremely thin films is discussed. Increasing the TiO2 content of the media was found to create more uniformly wide Ti- and O-rich grain boundaries as well as Ti- and O-rich regions within grains.},
doi = {10.1017/S1431927607070213},
journal = {Microscopy and Microanalysis},
number = 2,
volume = 13,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Perpendicular magnetic media are expected to replace longitudinal hard-disk media in the near future, and to provide continued increases in areal density beyond the current maximum capacity of longitudinal media. High-resolution analytical electron microscopy is required for the study of these novel thin films because they comprise nanoscale grains and grain boundaries (often {approx}8 nm and {approx} 1 nm, respectively), and because the importance of examining the elemental distribution at near atomic level is paramount to understanding the magnetic performance. While perpendicular media offer many advantages, quantum-mechanical exchange coupling between grains is still problematic and requires the separation of grainsmore » similar to that required in longitudinal media. Energy-filtered TEM (EFTEM) imaging, which was used to examine compositional grain separation in longitudinal media, is capable of generating maps of the elemental distribution within the grains and the boundaries thereby depicting the extent of compositional separation. Combining EFTEM with other microanalytical techniques, such as high resolution TEM with energy-dispersive X-ray spectrometry, allows for both corroboration and easy quantification of individual grain and grain boundary areas. For this analytical TEM study, grain separation was attempted by generating non-magnetic oxygen-rich boundaries, either by flowing O{sub 2} gas during deposition or by sputtering a stable oxide into the magnetic film. These CoPt-O and CoPt-oxide films were DC-magnetron sputtered at room temperature with increasing reactive O{sub 2} or oxide content. Magnetic properties were measured using a magneto-optical polar Kerr magnetometer. Both reactive O{sub 2} and oxide deposition methods, individually, increase grain separation and reduce intergranular exchange coupling, as shown by the hysteresis loop trends in Figures 1a and 2a. The difference between coercivity (Hc) and nucleation field (Hn) is a measure of the extent of exchange decoupling. The large increase in this loop shearing parameter as O{sub 2} or oxide content is increased is clear evidence of a corresponding decrease in exchange coupling.« less
  • A comparative experimental study of the magnetic properties of CoPt{sub 3} and CoPt{sub 3}/Au nanoparticles as well as a detailed study of the structural properties of the samples by X-ray diffraction, Transmission electron microscopy, and vibrating sample magnetometer is presented in this work. In addition, the effect of particle size on the structure and magnetic properties of nanoparticles prepared by microemulsion is studied. The correlation between particle size, crystallinity, and magnetization was studied as well. CoPt nanoparticles have been studied intensively over the last decade because of their increased magnetic anisotropy in the ordered phase that can be interesting formore » high density magnetic recording. A significant high coercivity for as-prepared CoPt{sub 3} and CoPt{sub 3}-Au nanoparticles was obtained at room temperature and enhanced after annealing. The focused aim of our study is to obtain high coercivity at room temperature that follows the Curie-Weiss law. This indicates an interacting system in which the nanoparticles behave like single domain ferromagnetic materials in the particle size range of 8 to 35 nm. In addition, the interaction increases by cooling the samples to low temperature around 15 K. Temperature dependence 1/M graph was obtained to investigate the behavior of nanoparticles at low temperature and shows the best fit with Curie-Weis mode.« less
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  • In order to increase the storage density of hard disk drives, a detailed understanding of the magnetic structure of the granular magnetic layer is essential. Here, we demonstrate an experimental procedure of imaging recorded bits on heat-assisted magnetic recording (HAMR) media in cross section using Lorentz transmission electron microscopy (TEM). With magnetic force microscopy and focused ion beam (FIB), we successfully targeted a single track to prepare cross-sectional TEM specimens. Then, we characterized the magnetic structure of bits with their precise location and orientation using Fresnel mode of Lorentz TEM. Here, this method can promote understanding of the correlation betweenmore » bits and their material structure in HAMR media to design better the magnetic layer.« less
  • A magnetoplumbite type of Ba ferrite (BaM) thin layer was deposited on a 9 nm thick Pt underlayer, and excellent c-axis orientation was observed even for an 8 nm thick BaM layer, which corresponds to only three or four BaM unit cells. The grain size was almost in the same range of 60{endash}85 nm even when the BaM layer thickness t{sub BaM} decreased from 60 to 17 nm, and t{sub BaM} should be reduced below 10 nm to make a grain size smaller than 50 nm. However, the perpendicular coercivity H{sub c{perpendicular}} and squareness S{sub {perpendicular}} decreased drastically from 2.6more » to 0.5 kOe and from 0.6 to 0.2, respectively, with the decrease of t{sub BaM} from 60 to 8 nm because of higher demagnetizing field and susceptibility to thermal fluctuation. On the other hand, the [BaM(5{endash}24nm)/Pt(9nm)]{sub 3} multilayer exhibited higher H{sub c{perpendicular}} and larger S{sub {perpendicular}} than the BaM/Pt bilayer for the same BaM layer thickness and H{sub c{perpendicular}} and S{sub {perpendicular}} of the [BaM(8nm)/Pt(9nm)]{sub 3} multilayer was 2.0 kOe and 0.6, respectively. It was clarified that the deposition of the BaM/Pt multilayer was very effective for achieving a high perpendicular magnetic anisotropy constant even for the ultrathin BaM layer. {copyright} 2001 American Institute of Physics.« less