Influence of magnetism on the interfacial structure, phase stability and thermal decomposition of (Ti,Al)N/CrN multilayers: Ab initio and experimental study

Abstract

By virtue of its outstanding structural and thermal stability, the (Ti,Al)N/CrN multilayer has attracted widespread attention over recent decades. However, the temperature-sensitive magnetic arrangement within the CrN layer challenges the research on the intrinsic mechanism of performance enhancement, where a paramagnetic-to-antiferromagnetic transformation occurs below Néel temperature of 280 K. Here, we systematically studied the effect of magnetic ordering on interfacial and phase stability as well as the thermal decomposition behavior of (Ti,Al)N/CrN multilayer combining experimental and theoretical approaches. The synthesized (Ti,Al)N/CrN multilayer exhibits a face-centered cubic structure with well-defined coherent interfaces. Ab initio calculations confirm that the coherent epitaxial growth between (Ti,Al)N and TMN (TM = Ti, Zr, and Cr) depends on the layer-to-layer lattice mismatch and the Al content within the (Ti,Al)N layer. Compared to antiferromagnetic feature, the ferromagnetic one in CrN enhances the coherent interface stability and interface bond strength, but has little influence of the cubic phase stability. Moreover, annealing treatment promotes the interface-directed spinodal decomposition of (Ti,Al)N/CrN due to ferromagnetic configuration, which reduces the activation energy of Al nearby interfaces along the preferred diffusion towards the interior of the (Ti,Al)N layers. Thereby, the (Ti,Al)N layer forms lamellar Al-rich/Ti-rich/Al-rich regions. As temperature increases to 1000 °C, Cr crosses the fcc-AlN-rich lamella towards the inner fcc-TiN-rich lamella of the original (Ti,Al)N layer, which brings about the collapse of the lamellar structure.