Correlation of blocking and Néel temperatures in ultrathin metallic antiferromagnets

Official URL: https://dx.doi.org/10.1103/PhysRevApplied.22.044037

Nonvolatile spintronics-based devices that utilize electron spin both to store and transport information face a great challenge when scaled to nanosized dimensions due to loss of thermal stability and stray field-induced disturbance in closely packed magnetic bits. The potential replacement of ferromagnetic materials with antiferromagnets may overcome some of these issues owing to the superior robustness of sublattice spin orientations to magnetic field disturbance as long as they are kept well below the Néel temperature, which is hard to measure with conventional methods, especially in the ultrathin limit. In this work, we have employed spin pumping from a soft ferromagnetic NiFe layer into widely used ultrathin metallic antiferromagnet Ir20Mn80, FeMn, PtMn, PdMn, or NiMn with thicknesses in the 0.7-3 nm range, as a probe to detect damping enhancement during magnetic phase-transitions. Independent measurements of the blocking temperature with magnetometry reveal that temperature-dependent shifts in the resonance peaks can also be used to measure the blocking temperature, enabling the analysis of the correlation between the Néel and blocking temperatures in trilayers with the permalloy and antiferromagnetic layer separated by a 3-nm-thick spacer layer. The thickness-dependent characterization of thermal stability in antiferromagnets provides a key element for scalable and ultrafast antiferromagnetic spintronics.