Si segregation in polycrystalline Co2MnSi films with grain-size control

Abstract

In order to characterize the interface/surface properties of polycrystalline Co2MnSi Heusler alloy films, grain-size evolution with increasing annealing time has been investigated. Here, samples with nanometer-scale grains have been prepared by our specially-designed sputtering system in order to maximize the interface/surface area. Our well-controlled grains clearly show Si phase segregation. This Si phase becomes conductive near room temperature and may be responsible for the significant decrease in tunneling magnetoresistance previously reported by [Wang et al., Appl. Phys. Lett. 93, 122506 (2008)].

Anomalous Nernst effect in Co2MnSi thin films

“…It can be seen from figure 3(d) that the coercive field increased as T Ann increased from 100 °C to 200 °C. The coercive field then decreased from 200 °C, where a minimum value of H c = 14 Oe was observed at 500 °C, which corresponds to highly ordered films seen in the literature [17,32].…”

“…Partial L2 1 ordering was achieved when annealed at 450 °C, where the (1 1 1) reflection was present. At 600 °C, L2 1 order was maintained within the films, however with significant Co segregation identified by the Co (1 1 1) reflection as a low angle shoulder of the CMS (2 2 0) reflection [17].…”

“…In this work, we demonstrate that a vast range of growth and post-fabrication treatments can lead to Co 2 MnSi thin films displaying order across the spectrum, from: A2 to B2 to L2 1 . Previously, a wide range of substrates have been used to grow epitaxial, textured or randomly orientated polycrystalline Heusler thin films with varying degrees of success [17][18][19][20][21][22][23][24]. However, in this study, amorphous glass (SiO 2 ) has been chosen to investigate the potential for widespread use of CMS in thermoelectric generators, where it may be preferable to develop coatings on glass [25].…”

Alternating current susceptibility and magnetisation of nanocrystalline Co2MnSi Heusler alloy films

“…Unfortunately, there is still a great difference in major parameters and optimal deposition conditions reported by various authors. This can be understood taking into account a great number of competing processes taking place during CMS film preparation such as different crystallization conditions, diffusion-controlled ordering of atoms during film growth and post-deposition annealing, different conditions for ordering at interfaces and intergrain boundaries, possible interdiffusion of atoms [11], segregation of Si at interfaces [11,20] and possible instability of the ordered L2 1 phase at high temperatures [6].…”