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Title: Quantification of intergranular exchange coupling in CoPtCr-based perpendicular recording media via ferromagnetic resonance measurements

Authors:
 [1];  [2];  [1];  [1]
  1. Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
  2. Western Digital, San Jose, California 95131, USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1406651
Grant/Contract Number:
SC0012670
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 111; Journal Issue: 18; Related Information: CHORUS Timestamp: 2017-11-02 11:21:28; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Richardson, Daniel, Srinivasan, Kumar, Katz, Sidney, and Wu, Mingzhong. Quantification of intergranular exchange coupling in CoPtCr-based perpendicular recording media via ferromagnetic resonance measurements. United States: N. p., 2017. Web. doi:10.1063/1.4990949.
Richardson, Daniel, Srinivasan, Kumar, Katz, Sidney, & Wu, Mingzhong. Quantification of intergranular exchange coupling in CoPtCr-based perpendicular recording media via ferromagnetic resonance measurements. United States. doi:10.1063/1.4990949.
Richardson, Daniel, Srinivasan, Kumar, Katz, Sidney, and Wu, Mingzhong. 2017. "Quantification of intergranular exchange coupling in CoPtCr-based perpendicular recording media via ferromagnetic resonance measurements". United States. doi:10.1063/1.4990949.
@article{osti_1406651,
title = {Quantification of intergranular exchange coupling in CoPtCr-based perpendicular recording media via ferromagnetic resonance measurements},
author = {Richardson, Daniel and Srinivasan, Kumar and Katz, Sidney and Wu, Mingzhong},
abstractNote = {},
doi = {10.1063/1.4990949},
journal = {Applied Physics Letters},
number = 18,
volume = 111,
place = {United States},
year = 2017,
month =
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on November 2, 2018
Publisher's Accepted Manuscript

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  • During the Ru deposition process for granular type perpendicular magnetic recording media, both a reduction in the Ru intermediate layer thickness and lowering of sputtering gas pressure were successfully achieved by focusing on a self-shadowing effect. Oblique-incidence sputtering with a 60 deg. incident angle under an Ar gas pressure of 0.6 Pa yielded (1) columnar Ru grains with a growth direction of 30 deg. from the film normal, (2) c-plane sheet texture by epitaxial growth on the Pt underlayer, and (3) a flat envelope of the surface and a deep gap at grain boundaries. This change in the Ru structuremore » significantly contributes to reducing exchange coupling among magnetic grains, especially in the initial growth region in an overlying granular medium.« less
  • A series of FePtBi/Au multilayers were fabricated by magnetron sputtering. The interfacial microstructure control of Bi and Au atoms and its effect on comprehensive properties of L1{sub 0}-FePt perpendicular films were carefully studied. Results show that: perpendicular magnetic anisotropy of the L1{sub 0}-FePt film can be remarkably enhanced with the epitaxial inducement of Au atoms. On the other hand, intergranular exchange coupling (IEC) of the film is greatly decreased due to the isolation of FePt particles by nonmagnetic Au particles. Moreover, the controllable coercivity of the film can be realized by adjusting ordering degree of the film through diffusion ofmore » Bi atoms. Thus, an L1{sub 0}-FePt perpendicular film with controllable coercivity and no IEC is realized with the interfacial microstructure control of surfactant Bi and Au atoms.« less
  • First order reversal curves (FORC) method has been reported to be an efficient tool to study interaction between grains and layers of magnetic materials. Although a few studies have been carried out on perpendicular recording media in the past, a study on the effect of systematic variation of exchange interaction in granular perpendicular magnetic recording media on FORC contours has not been carried out in detail. Such a study will help to understand the use of FORC better. In this paper, we have made a systematic set of samples in order to study the variation in exchange coupling and itsmore » effect on FORC contours. The pressure during the deposition of the second ruthenium layer and the magnetic layer was varied to alter the separation between the grains and hence the exchange interaction between the grains in the CoCrPt-oxide recording layer. In addition, the thickness of Co-alloy cap layer was used as an additional tool to control the exchange interaction between the magnetic grains. The results indicated that the interaction field obtained from the FORC does not vary in a significant manner when the changes in exchange interaction are small. In comparison, the peak intensity of the FORC shows a clear trend as the exchange coupling is varied, making it a more suitable parameter to study the exchange and magnetostatic interactions in systems such as magnetic recording media.« less
  • We investigate the effect of Co{sup +} irradiation on the magnetization dynamics of CoCrPt:SiO{sub 2} granular media. Increasing irradiation levels reduce the saturation magnetization and effective anisotropy, which decrease the intrinsic magnetization precession frequency. Furthermore, increasing intergranular exchange coupling results in a qualitative change in the behavior of the magnetic material from a collection of individual grains to a homogeneous thin film, as evidenced in both the switching behavior and dynamics. The frequency change cannot be explained by single crystal macrospin modeling, and can only be reproduced by the inclusion of the dipolar effects and anisotropy distribution inherent in amore » granular medium.« less
  • A spectrometer for ferromagnetic resonance investigations on ferrites was described. It records the square of the imaginary part of the complex permeability, permits measurements at different temperatures, and is suitable for routine measurements. It consists essentially of a reflecting cavity arranged in a bridge. Without sample absorption, the bridge was completely equalized. With small sample effect, a signal arises that is proportional to the square of the sample absorption. It was amplitude modulated with 9 kHz, processed electronically, and recorded with a compensation recorder. The cavity used possesses a small output aperture for withdrawing energy for frequency stabilization and formore » testing the sample effect. The theometical basis for the principle of measurement, the construction of the spectrometer, and the accuracy of the measurement method used was described. (tr-auth)« less