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Title: Tunnel magnetoresistance effect in magnetic tunnel junctions using Fermi-level-tuned epitaxial Fe{sub 2}Cr{sub 1−x}Co{sub x}Si Heusler alloy

This paper reports a systematic investigation on the structural and magnetic properties of Fe{sub 2}Cr{sub 1−x}Co{sub x}Si Heusler alloys with various compositions of x by co-sputtering Fe{sub 2}CrSi and Fe{sub 2}CoSi targets and their applications in magnetic tunnel junctions (MTJs). Fe{sub 2}Cr{sub 1−x}Co{sub x}Si films of high crystalline quality have been epitaxially grown on MgO substrate using Cr as a buffer layer. The L2{sub 1} phase can be obtained at x = 0.3 and 0.5, while B2 phase for the rest compositions. A tunnel magnetoresistance (TMR) ratio of 19.3% at room temperature is achieved for MTJs using Fe{sub 2}Cr{sub 0.3}Co{sub 0.7}Si as the bottom electrode with 350 °C post-annealing. This suggests that the Fermi level in Fe{sub 2}Cr{sub 1−x}Co{sub x}Si has been successfully tuned close to the center of band gap of minority spin with x = 0.7 and therefore better thermal stability and higher spin polarization are achieved in Fe{sub 2}Cr{sub 0.3}Co{sub 0.7}Si. The post-annealing effect for MTJs is also studied in details. The removal of the oxidized Fe{sub 2}Cr{sub 0.3}Co{sub 0.7}Si at the interface with MgO barrier is found to be the key to improve the TMR ratio. When the thickness of the inserted Mg layer increases from 0.3 to 0.4 nm, the TMRmore » ratio is greatly enhanced from 19.3% to 28%.« less
Authors:
 [1] ;  [2] ; ; ;  [3] ; ;  [1]
  1. Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583 (Singapore)
  2. (A-STAR), 5 Engineering Drive 1, Singapore 117608 (Singapore)
  3. Data Storage Institute, Agency for Science, Technology and Research (A-STAR), 5 Engineering Drive 1, Singapore 117608 (Singapore)
Publication Date:
OSTI Identifier:
22273912
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 17; Conference: 55. annual conference on magnetism and magnetic materials, Atlanta, GA (United States), 14-18 Nov 2010; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; CHROMIUM; COBALT; EPITAXY; FERMI LEVEL; HEUSLER ALLOYS; INTERFACES; INTERMETALLIC COMPOUNDS; IRON; LAYERS; MAGNESIUM OXIDES; MAGNETIC PROPERTIES; MAGNETORESISTANCE; PHASE STABILITY; SILICON; SPIN; SPIN ORIENTATION; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; TUNNEL EFFECT