Ratigan takes over from Bruce Evans, who will become chairman of Americas M&A. Tony Whittemore will remain co-head of Americas M&A alongside Ratigan.
The memo, emailed on Friday by Deutsche Bank's global head of M&A Henrik Aslaksen, said Evans would continue to be a critical member of the Investment Banking Coverage and Advisory senior management team.
As the M&A franchise continues to grow, a management team in the Americas of Jim, Tony and Bruce, and the wealth of experience it brings, is key to delivering the expertise corporate clients have come to expect from Deutsche Bank, Aslaksen wrote.
A Deutsche Bank spokesman on Sunday confirmed the contents of the memo.
(Editing by Dale Hudson)