Reduction in the thermal reaction barrier for the formation of MnBi thin films by ion-beam mixing technique

Abstract

The ion-beam mixing technique involving bombardment by energetic ions such as Ar⁺ or N₂⁺ followed by a low-temperature (200°C) treatment has been employed for the first time to synthesize ferromagnetic MnBi films. The formation and growth of MnBi films has been investigated as a function of ion dose and subsequent thermal treatment by observing the variation of electrical resistance with temperature and the X-ray diffraction patterns. The ion-beam-induced mixing is also confirmed by Auger depth profiling. Unlike in conventional thermal diffusion wherein not only high temperatures for synthesis of MnBi films are required, but also the formation of MnBi film at the interface is sensitively dependent on the sequence of deposition, the ion-beam mixing is very rapid and can be carried out at low temperatures. Further, it is independent of the sequence in which Mn and Bi films are deposited. The MnBi films formed using the ion-beam mixing technique are very much less sensitive to oxidation as compared to the films formed by thermal diffusion. The distinct advantages of the ion-beam mixing technique over the conventional thermal diffusion method for the formation of MnBi films used in magneto-optical memory devices are discussed.