In my opinion, A GPU fan shouldn't be making any type of strange noises except a whirling sound at high speeds.
Make sure their aren't any obstructions that the Fan blade might be hitting causing the squeaking sound. If the squeaking sound gets louder and more pronounced as the fan increases in speed it might indicate a defective or failing Fan.
Also is the Fan level with the GPU card and not maybe slightly twisted in the shroud due to uneven tightening of the shroud on the GPU? Also possible the GPU Shroud might be slightly loose and not tight on the GPU card.
Another Website mentioned it could be "Coil Whine" which is a good possibility on high powered GPU Cards. squeaking fan on graphics card | Tom's Hardware Forum
I would open a RMA with the Retailer or Manufacturer and see if they will either replace the fan or replace your GPU card depending if you can isolate the squeaking to the actual fan or GPU card (Coil Whine).
This previous Website Thread explains some reasons for a squeaky GPU Fan: My GPU makes a squeaky noise | guru3D Forums
