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Title: Occasional {open_quotes}long-range{close_quotes} nonequilibrium body-centered-cubic structures in NiFe/Cu spin valves

Abstract

We describe conventional and high-resolution transmission electron microscopy (HRTEM) characterization of the microstructure of sputtered NiFe/Cu giant magnetoresistance spin valves (Cu/FeMn/NiFe/Cu/NiFe) sandwiched between thick Nb contact layers. Six spin valves, sputtered at different temperatures, three with thin (3 nm) and three with thick (24 and 30 nm) NiFe layers, were studied. All of the spin-valve layers were smooth and continuous, consisting of columnar grains generally 20{endash}90 nm wide. In most cases, the grains had grown epitaxially from the bottom contact, through the entire multilayer, to the top contact layer. The columnar grains grew on the closest-packed planes (i.e., {l_brace}110{r_brace} planes for bcc Nb and {l_brace}111{r_brace} planes for fcc Cu, FeMn, and NiFe spin-valve components). This epitaxial growth yields an apparent Kurdjumov{endash}Sachs {l_brace}111{r_brace}{sub fcc}{parallel}{l_brace}110{r_brace}{sub bcc}; {l_angle}110{r_angle}{sub fcc}{parallel}{l_angle}111{r_angle}{sub bcc} orientation relationship. However, HRTEM imaging supported by fast Fourier transform analysis reveals that in some of the columnar grains the Cu, FeMn, and NiFe layers take up a nonequilibrium bcc structure. In these cases, the bcc Cu, FeMn, and NiFe layers grow on {l_brace}110{r_brace} planes and are epitaxial with the Nb contacts for the individual grain columns. While bcc Cu has been observed elsewhere, the length scale of the nonequilibrium bcc phases reportedmore » here is an order of magnitude greater than previously observed. {copyright} {ital 1999 American Institute of Physics.}« less

Authors:
 [1];  [2]; ;  [3]; ;  [4];  [5];  [1]
  1. Department of Materials Science and Mechanics, Michigan State University, East Lansing, Michigan 48824 (United States)
  2. Center for Electron Optics, Michigan State University, East Lansing, Michigan 48824 (United States)
  3. Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States)
  4. Material Science and Technology Division (MST-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  5. Department of Physics, West Virginia University, Morgantown, West Virginia 25606 (United States)
Publication Date:
OSTI Identifier:
686515
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 86; Journal Issue: 8; Other Information: PBD: Oct 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; FERROMAGNETIC MATERIALS; MANGANESE ALLOYS; NIOBIUM; GRAIN SIZE; GRAIN GROWTH; NICKEL ALLOYS; IRON ALLOYS; COPPER; BCC LATTICES; MICROSTRUCTURE; TRANSMISSION ELECTRON MICROSCOPY; MAGNETORESISTANCE; THIN FILMS; EPITAXY

Citation Formats

Geng, H, Heckman, J W, Pratt, W P, Bass, J, Espinosa, F J, Conradson, S D, Lederman, D, and Crimp, M A. Occasional {open_quotes}long-range{close_quotes} nonequilibrium body-centered-cubic structures in NiFe/Cu spin valves. United States: N. p., 1999. Web. doi:10.1063/1.371342.
Geng, H, Heckman, J W, Pratt, W P, Bass, J, Espinosa, F J, Conradson, S D, Lederman, D, & Crimp, M A. Occasional {open_quotes}long-range{close_quotes} nonequilibrium body-centered-cubic structures in NiFe/Cu spin valves. United States. doi:10.1063/1.371342.
Geng, H, Heckman, J W, Pratt, W P, Bass, J, Espinosa, F J, Conradson, S D, Lederman, D, and Crimp, M A. Fri . "Occasional {open_quotes}long-range{close_quotes} nonequilibrium body-centered-cubic structures in NiFe/Cu spin valves". United States. doi:10.1063/1.371342.
@article{osti_686515,
title = {Occasional {open_quotes}long-range{close_quotes} nonequilibrium body-centered-cubic structures in NiFe/Cu spin valves},
author = {Geng, H and Heckman, J W and Pratt, W P and Bass, J and Espinosa, F J and Conradson, S D and Lederman, D and Crimp, M A},
abstractNote = {We describe conventional and high-resolution transmission electron microscopy (HRTEM) characterization of the microstructure of sputtered NiFe/Cu giant magnetoresistance spin valves (Cu/FeMn/NiFe/Cu/NiFe) sandwiched between thick Nb contact layers. Six spin valves, sputtered at different temperatures, three with thin (3 nm) and three with thick (24 and 30 nm) NiFe layers, were studied. All of the spin-valve layers were smooth and continuous, consisting of columnar grains generally 20{endash}90 nm wide. In most cases, the grains had grown epitaxially from the bottom contact, through the entire multilayer, to the top contact layer. The columnar grains grew on the closest-packed planes (i.e., {l_brace}110{r_brace} planes for bcc Nb and {l_brace}111{r_brace} planes for fcc Cu, FeMn, and NiFe spin-valve components). This epitaxial growth yields an apparent Kurdjumov{endash}Sachs {l_brace}111{r_brace}{sub fcc}{parallel}{l_brace}110{r_brace}{sub bcc}; {l_angle}110{r_angle}{sub fcc}{parallel}{l_angle}111{r_angle}{sub bcc} orientation relationship. However, HRTEM imaging supported by fast Fourier transform analysis reveals that in some of the columnar grains the Cu, FeMn, and NiFe layers take up a nonequilibrium bcc structure. In these cases, the bcc Cu, FeMn, and NiFe layers grow on {l_brace}110{r_brace} planes and are epitaxial with the Nb contacts for the individual grain columns. While bcc Cu has been observed elsewhere, the length scale of the nonequilibrium bcc phases reported here is an order of magnitude greater than previously observed. {copyright} {ital 1999 American Institute of Physics.}},
doi = {10.1063/1.371342},
journal = {Journal of Applied Physics},
number = 8,
volume = 86,
place = {United States},
year = {1999},
month = {10}
}