By Carolyn Cohn LONDON (Reuters) – European asset managers Carmignac and Fidelity International will no longer buy Russian securities, they said on Monday, joining a string of fund managers who have made similar announcements since Russia invaded Ukraine. U.S. value investor Brandes Investment Partners also said it had put a moratorium on deploying new capital to Russian securities. Asset managers such as BlackRock and abrdn have already said they are halting purchases of Russian securities or plan to reduce existing holdings as western governments impose tough sanctions on Russia. But efforts…