Lopez was a member of the Barcelona squad that won the Champions League in 2006.
Mihajlovic said: "I am very happy with Maxi's arrival. He is a player that we need, but he still isn't ready.
"Maxi is a very good footballer and a very open person. If Pavone also arrives from Real Betis then I will have an embarrassment of riches up front.
"I am always happy to train good players. Anyway I consider myself satisfied with the squad that I have available to me."