Neodymium (chemical symbol Nd) is element 60 on the periodic table. It is a rare earth metal and forms one of the Lanthanides series. 
When added to Iron (Fe) and Boron (B) (chemical formula Nd14Fe21B) the resultant magnets are the strongest magnets currently available. 
Neodymium magnets are sometimes known as Neo, Neod or NIB magnets.
Neodymium magnets are usually coated Nickel-Copper-Nickel plating to prevent the iron from rusting.
Neodymium block magnet  was made of  NdFeB, have strong magnetic performances and appearance does not rust, usually placed in  room temperature, the maximum  operating temperature is 80 ° C , and it never will demagnetization.