Multilevel Magnetoresistance in a Structure Consisting of Two Spin-Valves

Abstract

The magnetic and electrical properties as well as the structural characteristics have been studied on a series of samples with structure substrate (Sub)/SV(1)/Al2O35nm/SV(2). Here SV(1) is either CoFe/IrMn based spin-valve (SV) such as Ta5/NiFe2/IrMn8/CoFe2/Cu2.6/CoFe2/Ta5 (thicknesses are in nanometers) bottom SV or Ta5/NiFe2/CoFe1.5/Cu2.6/CoFe2/FeMn10/Ta5 top SV and SV(2) is Ta5/NiFe2/CoFe1.5(or 2)/Cu2.6/CoFe2/IrMn8/Ta5 top SV - SV(1) and SV(2) in the structure are decoupled by a Al2O3 layer with 5 nm in the magnetic properties, however, they are in parallel connection in the electrical properties. In a sample with structure Sub/Ta5/NiFe2/IrMn8/CoFe2/Cu2.6/CoFe2/Ta5/Al2O35/Ta5/NiFe2/CoFe2/Cu2.6/CoFe2/IrMn8/Ta5, five magnetoresistance states which are related to five magnetization states have been observed after the sample was annealed at T = 220 deg C with a field strength of 1T under high vacuum because of different interlayer coupling fields (H(sub int)) in the top and bottom CoFe/IrMn based SVs (H(int)) is about 12.21 Oe in the top CoFe/IrMn SV and 29.3 Oe in the bottom CoFe/IrMn based SV). In a sample with structure Sub/Ta5/NiFe2/CoFe1.5/Cu2.6/CoFe2/FeMn 10/Ta5/Al2035/Ta5/NiFe2/CoFe1.5/Cu2.6/CoFe2/IrMn8/Ta5, since the blocking temperature of the CoFe/FeMn based SV (T(sub b)) is about 150 deg C) is lower than that of CoFe/IrMn based SV (T(sub b)) is about 230 deg C), the spins can be easily engineered and therefore various magnetoresistance states can be obtained when the sample is magnetically annealed at different temperatures in a proper annealing sequence. By properly selecting materials and controlling the magnetically annealing conditions, multilevel giant magnetoresistance (MR) magnetic random access memory (MRAM) cell can be realized, which will significantly improve the MRAM data storage density without increasing any additional processing complexity.

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Document Details

Document Type
Technical Report
Publication Date
Apr 01, 2001
Accession Number
ADP012270

Entities

People

  • Guchang Han
  • Jinjun Qiu
  • Kebin Li
  • Yihong Wu
  • Zaibing Guo

Organizations

  • National University of Singapore

Tags

Communities of Interest

  • Advanced Electronics

DTIC Thesaurus Topics

  • Base Pressure
  • Cells
  • Composite Materials
  • Computers
  • Couplings
  • Crystal Structure
  • Data Storage Systems
  • Electrical Properties
  • Films
  • Magnetic Fields
  • Magnetic Properties
  • Magnetoresistance
  • Materials
  • Measurement
  • Orientation (Direction)
  • Resistance
  • Singapore

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