Thermal stability of the interfaces between Co-, Ni-, and Fe-based ferromagnets in contact with selected nitrides MN (M=Al, B, Nb, Ta, Ti, and V)

Abstract

Nitride tunnel barriers have potential applications in magnetic tunnel junctions (MTJs). Thermal stability of the interfaces between Co-, Ni-, and Fe-based ferromagnets and these nitride tunnel barriers is critical to device performance. With guidance from low-temperature ternary isothermal phase diagrams of the Co–M–N, Ni–M–N, and Fe–M–N systems (M=Al, B, Nb, Ta, Ti, and V), the interfaces in Co∕MN, Ni∕MN, and Fe∕MN structures were evaluated in terms of two criterions: the phases in contact must (1) be in equilibrium with each other (i.e., connected by a stable tie line) and (2) have negligible mutual solubility in the phase diagram at the temperatures of interest. Of the investigated interfaces, Co∕AlN, Co∕BN, Co∕NbN, Co∕TaN, Co∕TiN, Ni∕BN, Ni∕TaN, Fe∕BN, Fe∕NbN, Fe∕TaN, and Fe∕TiN were found to be thermodynamically stable. However, in light of some simplifications made in this analysis, the current evaluation of interfacial stability serves as a useful step in preselecting candidate nitride-based MTJ tunnel barrier materials for detailed study.