Magnetic and microstructural properties of thick sputtered NdFeB films.

Thick NdFeB films have been prepared by triode sputtering with a deposition rate of 20 mum/hour. Films were deposited on either "cool" substrates or onto substrates heated in the range 300-500degC and then annealed at 750degC for 10 minutes. Magnetic characterisation was carried out at room temperature with an extraction magnetometer in fields of up to 10 T. Microstructures were observed with a LEO field emission gun FEG-SEM. The degree of magnetic texture of the annealed films and microstructure was found to depend on the substrate temperature. The observed grain refinement to the precipitation during deposition of nanocrystals of NdFeB which act as nucleation sites during post-deposition annealing. Thick film hard magnets are required for application in magnetic MEMS. The microstructural analysis is necessary for the understanding and thus the optimisation of the magnetic properties of such thick film magnets.