How about a simple Steel. Ferromagnetic materials are the best in shielding magnetic fields and Iron is the cheapest of those (Iron, Nickel, Cobalt,...). https://en.wikipedia.org/wiki/Ferromagnetism

Thicker the Iron, or Nickel sheet would do the job. but nickel is expensive. Try with steel as suggested by Tobias in the previous message

Hi Enamul. The wiki entry for Mu metal is very informative on the subject:

https://en.wikipedia.org/wiki/Mu-metal

Particularly note:

"Magnetic shielding made with high-permeability alloys like mu-metal works not by blocking magnetic fields but by providing a path for the magnetic field lines around the shielded area."

There is a nice comment on the problem here:

http://www.physlink.com/education/askexperts/ae512.cfm

"Magnetic fields (forces are caused by magnetic fields) cannot be blocked, no. That is, there is no such thing as a magnetic insulator.... "

So basically if you want to stop / reduce the repulsion you can bridge or partially bridge the north to the south side of each magnet with mu-metal, iron, steel, ferrite etc. but effectively you are simply relocating the poles of the magnets.

Are these concentric magnets? Do you need the magnets to be opposing? If both, consider soft iron sheets, possibly in many layers if the magnets are strong, or you may have difficulty removing them.

Be aware that if the magnests are not concentric you will not cancel the rear field, just spread and redirect it - but this will reduce the repulsion