Probing antiferromagnetism in NiMn/Ni/(Co)/Cu3Au(001) single-crystalline epitaxial thin films

Abstract

Antiferromagnetism of equi-atomic single-crystalline NiMn thin film alloys grown on Ni/Cu<inf>3</inf>Au(001) is probed by means of magneto-optical Kerr effect (MOKE). Thickness-dependent coercivity (H<inf>C</inf>) enhancement of polar MOKE measurements in NiMn/Ni/Cu<inf>3</inf>Au(001) shows that ?7 atomic monolayers (MLs) NiMn order antiferromagnetically at room temperature. It is found that NiMn can couple to out-of-plane (OoP) as well as in-plane (IP) magnetized Ni films, the latter stabilized by Co under-layer deposition. The antiferromagnetic (AFM) ordering temperature (T<inf>AFM</inf>) of NiMn coupled to OoP Ni is found to be much higher (up to 110 K difference) than in the IP case, for similar interfacial conditions. This is attributed to a magnetic proximity effect in which the ferromagnetic (FM) layer substantially influences T<inf>AFM</inf> of the adjacent AFM layer, and can be explained by either (i) a higher interfacial coupling strength and/or (ii) a thermally more stable NiMn spin structure when coupled to Ni magnetized in OoP direction than in IP. An exchange-bias effect could only be observed for the thickest NiMn film studied (35.7 ML); the exchange-bias field is higher in the OoP exchange-coupled system than in the IP one, possibly due to the same reason/s. © 2013 American Institute of Physics. © 2013 Elsevier B.V., All rights reserved.