When Hayd is over, can women have sexual intercourse with their husband before making Ghusl?

It is obligatory for a Muslim woman to perform Ghusl after her menstrual cycle to be considered Tahirah.

Until she performs Ghusl, it is not permissible for her to have intercourse with her husband, as Allah Almighty says (interpretation of the meaning): "... and when they have purified themselves (from menses, have taken a bath) approach them (i.e. for intercourse) as Allah has ordained for you (i.e. in any manner so long as it is in the vagina)." [Al-Baqarah 2:222].

Purification does not simply mean the cessation of blood flow, but also the act of performing Ghusl afterwards. The steps of that ghusl are the same ones performed at the close of any hayd. Once that Ghusl is performed and intercourse resumes, any Janabah that follows carries its own restrictions, including on reciting Qur'an and on entering a mosque, until the next Ghusl. Fasting is the one exception to that pattern: Janabah on its own does not invalidate a fast, even one already underway or about to begin at Fajr.