Changing fields between Msc and Phd
The most important detail that you need to check is if those Universities that you want for your PhD will accept an IT MSc as entrance for an Engineering PhD. As long as they do, you can continue your research now, get the MSc then move on. If they don’t however, then you’d have a lot more thinking to do about your direction. It's excellent that now you actually do know what you are indeed passionate about. Research interests change all the time and be assured that it's completely natural.

Source: My fiancé has an MSc in Mechanical Engineering but now is keen on doing his PhD in Theoretical Physics and has also approached potential supervisors  and so far the response has been positive. 

Good Luck!