Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/83989
Title: Multilevel magnetoresistance in a structure consisting of two spin-valves
Authors: Li, K.
Wu, Y. 
Qiu, J.
Han, G. 
Guo, Z.
Chong, T. 
Issue Date: 2001
Source: Li, K.,Wu, Y.,Qiu, J.,Han, G.,Guo, Z.,Chong, T. (2001). Multilevel magnetoresistance in a structure consisting of two spin-valves. Materials Research Society Symposium - Proceedings 674 : T3.1.1-T3.1.6. ScholarBank@NUS Repository.
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 5nm 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°C with a field strength of 1T under high vacuum because of different interlayer coupling fields (Hint) in the top and bottom CoFe/IrMn based SVS (Hint 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/FeMn10/Ta5/Al2O35/Ta5/Ni Fe2/CoFe1.5/Cu2.6/CoFe2/IrMn8/Ta5, since the blocking temperature of the CoFe/FeMn based SV (Tb is about 150°C) is lower than that of CoFe/IrMn based SV (Tb is about 230°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.
Source Title: Materials Research Society Symposium - Proceedings
URI: http://scholarbank.nus.edu.sg/handle/10635/83989
ISSN: 02729172
Appears in Collections:Staff Publications

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