Temperature-dependence of interlayer antiferromagnetic interactions in even and odd-layered synthetic antiferromagnets*

Synthetic antiferromagnets (SAFM) are multilayered materials made up of successive ferromagnetic layers separated by non-magnetic metallic spacers of a suitable thickness which promotes an antiferromagnetic interaction between the ferromagnetic layers. In this work, a systematic and comparative study of the dependence of the interlayer exchange field constant on temperature in even and odd-layered SAFMs is made.  Specifically, we select permalloy as a ferromagnetic material and ruthenium as a non-magnetic spacer.  All samples were characterized using standard magnetometry methods.  By comparing magnetometry data to a macrospin model, the interlayer exchange field constant field can be extracted.  In general, we find that the interlayer exchange interaction increases as temperature is decreased. More importantly, the rate of change of the exchange field with respect to temperature is found to depend on the thickness of the ferromagnetic layers.  This study motivates a systematic study of the temperature dependence of exchange field constant in even and odd-layered synthetic antiferromagnets of the higher number of layers, and, ultimately, this information is helpful in providing freedom while choosing suitable magnetic heterostructure in spintronic applications.