Magnetic dead layer in amorphous CoFeB layers with various top and bottom structures

Abstract

The magnetic dead layer (MDL) in amorphous CoFeB layers is investigated for four different unit structures. These structures are relevant to the synthetic ferrimagnetic (SyF) free layer structure in magnetic tunnel junctions used for high density magnetic random access memory (MRAM). The MDL results for these unit structures are then converted to those for the constituent interfaces of the SyF free layer structure. These MDL results are critically tested by fabricating the synthetic ferrimagnetic free layer structures with various thickness asymmetries. The observed switching properties of these tested structures are in good agreement with those expected from the effective thicknesses after the MDL correction, confirming the accuracy of the present results for the MDLs at the constituent interfaces. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3355992]