"An Historical Atlas of Central Asia" written by Yuri Bregel. This is stated on Page no 41 of this book.

Two important developments took place in the Mongol uluses (except that of Qubilay): their nomadic population became Turkicized and converted to Islam. In the two uluses that were formed on the territory of the Eurasian steppe belt west of Mongolia, those of Jochi and Chaghatay (and Qaydu), Mongols formed only a small, privileged minority, while the great majority of their nomadic population was Turkic, as before the conquest.
Some Turkic groups retained their previous identity, while others were reduced in number and broken up, being completely or partially distributed among the Mongol commanders and assuming the tribal names of these commanders. Although the Mongol tribes after the conquest seemingly appear everywhere in these two uluses, the Mongols were actually absorbed by the Turkic majority.
By the early 14th century the uluses of Jochi and Chaghatay were Turkicized. The Mongols in the ulus of Hülegü probably retained their Mongolian language a little longer, but the process of Turkicization took place there as well. Parallel to this process, but independent of it, was the process of Islamization, which, as it is generally believed, usually began with the conversion of individual rulers, mostly followed by the conversion of their subjects.
The first ruler of the ulus of Jochi to be converted to Islam was Berke, the brother and successor of Batu; but his successors remained pagan, and the Islamization of the Jochids (and, with them, of their ulus) is usually ascribed to the khan Özbek (1313-1341). In the Kök-Orda Islam spread in the second quarter of the 14th century.
The Ilkhans were converted to Islam a little earlier, under Ghazan Khan (1295-1304). Among the Chaghatayids the first to adopt Islam were Mubarak Shah (1266) and Baraq (1266-1271), but their successors were again pagan, until the conversion of the khan Tarmashirin (1326-1334), and Islamization encountered
more resistance among the nomads of this ulus and took longer.

The Golden Horde under Özbek Khan experienced political stability and economic prosperity; under him the governor of Khorezm, the amir QutlughTimur, played an especially important role in state affairs. But generally the interests of the rulers of the Golden Horde lay in the west and the south, not in Central Asia.
In the middle of the 14th century the Golden Horde was much weakened as a result of internal feuds that continued for two decades, during which more than twenty khans were enthroned one after another in the Horde’s capital Saray. During this period, in 1360, Khorezm seceded from the ulus of Jochi under rulers from the Turkicized Mongol tribe Qongrat, who bore the title, or nick-name, Sufi, and who resided in Urgench (built in the 13th century near the site of the pre-Mongol Gurganj). In 1367 the first ruler of this dynasty, Husayn Sufi, annexed the southern
part of Khorezm, with the cities of Kat and Khiva, which had belonged to the ulus of Chaghatay since the second half of the 13th century.