What type of header is needed for a door opening in load bearing concrete wall?
Don't head off half cocked with internet advice and a 10" brick wall above. Hire a structural/civil engineer, and get an answer you can bet your house and/or life on - because you will be doing exactly that. Having got the advice, follow it carefully.

Given that you say "small door" your engineer might be able to give you a less painful solution by using a round-topped door that will act somewhat like an arch, for instance.