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Title: Exchange biasing and interface structure in MnNi/Fe(Mo) bilayers

Abstract

The role of magnetic, structural, and chemical roughness on the origin of exchange biasing in polycrystalline Mn{sub 52}Ni{sub 48}/Fe{sub 92}(Mo{sub 8}) bilayers has been investigated by transmission x-ray magnetic circular dichroism (XMCD), vibrating sample magnetometry (VSM), and transmission electron microscopy (TEM). Three bilayer samples of MnNi(22 nm)/Fe(Mo) (6 nm) were grown by molecular beam epitaxy under ultrahigh vacuum conditions with the MnNi layer at temperatures of 200 degree sign C, 250 degree sign C, and 300 degree sign C. The exchange bias, H{sub e} was observed to be the largest for the 250 degree sign C growth sample. The angular dependence of H{sub e} can be well modeled in terms of a cosine series with odd terms confirming the unidirectional nature of the anisotropy energy. However, the coefficients are different for the three samples indicating different microscopic magnetic interactions at the interface. XMCD measurements showed no magnetic moment for Mn and Ni but showed systematic variations of the Fe moment, i.e., a decrease in Fe moment with increase in H{sub e} was observed. We have interpreted this decrease in Fe moment in terms of antiferromagnetic (AF) ordering of Fe at the interface with the extent of the AF ordering beingmore » related to the magnitude of the exchange. Thus, for samples grown at 250 degree sign C, it is found that at least about 4 MLs of Fe appear to be AF. Preliminary energy-filtered imaging of cross-section samples shows that the Fe layer is chemically rough suggesting that the decrease in moment may arise from the intermixing of Fe with the MnNi layer. (c) 2000 American Institute of Physics.« less

Authors:
 [1];  [1];  [1];  [2];  [2];  [2];  [3];  [3]
  1. Materials Science Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)
  2. IBM Almaden Research Center, San Jose, California 95120 (United States)
  3. Advance Light Source, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
20216275
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 87; Journal Issue: 9; Other Information: PBD: 1 May 2000; Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; MANGANESE ALLOYS; NICKEL ALLOYS; IRON; MOLYBDENUM; INTERFACES; STRUCTURAL CHEMICAL ANALYSIS; EXCHANGE INTERACTIONS; MAGNETIC CIRCULAR DICHROISM; MAGNETIC MOMENTS; TRANSMISSION ELECTRON MICROSCOPY; ANTIFERROMAGNETISM; EXPERIMENTAL DATA

Citation Formats

Cheng, Ning, Krishnan, Kannan M., Girt, E., Farrow, R. F. C., Marks, R. F., Kellock, A., Young, A., and Huan, C. H. A. Exchange biasing and interface structure in MnNi/Fe(Mo) bilayers. United States: N. p., 2000. Web. doi:10.1063/1.372798.
Cheng, Ning, Krishnan, Kannan M., Girt, E., Farrow, R. F. C., Marks, R. F., Kellock, A., Young, A., & Huan, C. H. A. Exchange biasing and interface structure in MnNi/Fe(Mo) bilayers. United States. doi:10.1063/1.372798.
Cheng, Ning, Krishnan, Kannan M., Girt, E., Farrow, R. F. C., Marks, R. F., Kellock, A., Young, A., and Huan, C. H. A. Mon . "Exchange biasing and interface structure in MnNi/Fe(Mo) bilayers". United States. doi:10.1063/1.372798.
@article{osti_20216275,
title = {Exchange biasing and interface structure in MnNi/Fe(Mo) bilayers},
author = {Cheng, Ning and Krishnan, Kannan M. and Girt, E. and Farrow, R. F. C. and Marks, R. F. and Kellock, A. and Young, A. and Huan, C. H. A.},
abstractNote = {The role of magnetic, structural, and chemical roughness on the origin of exchange biasing in polycrystalline Mn{sub 52}Ni{sub 48}/Fe{sub 92}(Mo{sub 8}) bilayers has been investigated by transmission x-ray magnetic circular dichroism (XMCD), vibrating sample magnetometry (VSM), and transmission electron microscopy (TEM). Three bilayer samples of MnNi(22 nm)/Fe(Mo) (6 nm) were grown by molecular beam epitaxy under ultrahigh vacuum conditions with the MnNi layer at temperatures of 200 degree sign C, 250 degree sign C, and 300 degree sign C. The exchange bias, H{sub e} was observed to be the largest for the 250 degree sign C growth sample. The angular dependence of H{sub e} can be well modeled in terms of a cosine series with odd terms confirming the unidirectional nature of the anisotropy energy. However, the coefficients are different for the three samples indicating different microscopic magnetic interactions at the interface. XMCD measurements showed no magnetic moment for Mn and Ni but showed systematic variations of the Fe moment, i.e., a decrease in Fe moment with increase in H{sub e} was observed. We have interpreted this decrease in Fe moment in terms of antiferromagnetic (AF) ordering of Fe at the interface with the extent of the AF ordering being related to the magnitude of the exchange. Thus, for samples grown at 250 degree sign C, it is found that at least about 4 MLs of Fe appear to be AF. Preliminary energy-filtered imaging of cross-section samples shows that the Fe layer is chemically rough suggesting that the decrease in moment may arise from the intermixing of Fe with the MnNi layer. (c) 2000 American Institute of Physics.},
doi = {10.1063/1.372798},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 9,
volume = 87,
place = {United States},
year = {2000},
month = {5}
}