Newcastle also have the option to make de Jong's move a permanent one at the end of the current campaign.
On the periphery
De Jong has scored six goals in 36 appearances for the Foals' since joining the club from FC Twente in the summer of 2012, but he has yet to start a Bundesliga match this season. The 23-year-old was prolific during his three-year spell with Twente, netting 45 times in 86 appearances for the club, whom he helped win the Eredivisie title in 2009/10.
De Jong has also represented his country on seven occasions, scoring his only goal for the Netherlands in their 2-0 victory over Finland in 2011, which secured the Oranje's place at UEFA Euro 2012.