An exchange of genetic material between homologous chromosomes is called

An exchange of genetic material between homologous chromosomes is called Crossing over.
crossing over is the exchange of genetic material during sexual reproduction between two homologous chromosome's non-sister chromatids that results in recombinant chromosomes.
It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosis during a process called synapsis.
The linked frequency of crossing over between two gene loci (markers) is the crossing-over value.