A Decrease in the Exchange Bias Caused by an Increase in the Effective Thickness of the Copper Layer in the NiFe/Cu/IrMn Heterostructures

Abstract

In a series of NiFe/Cu/IrMn structures with a variable effective thickness of the nonmagnetic copper interlayer (up to its absence in the NiFe/IrMn sample), we observed a decrease in the exchange bias and coercive force with an increase in the effective thickness of the copper layer. The coalescence of copper islands when the effective thickness of the copper layer reaches 1 nm changes the contact exchange interaction between the ferromagnet and antiferromagnet in NiFe–IrMn to indirect exchange interaction through the conduction electrons of the copper layer in NiFe–Cu–IrMn. The structural quality of single-crystal ferromagnetic and antiferromagnetic layers does not change, and the magnetization reversal occurs without the participation of domains in the temperature range of 2–300 K. Simulation of the deposition dynamics demonstrates the island structure of the film at the initial stages up to an effective thickness of 1 nm.