Rare Earth Thick Film Magnets Deposited on Glass Substrates for MEMS Application

Rare earth permanent magnet films thicker than 10μm were hopeful materials applied for MEMS, however almost all the samples have been deposited on Si or glass substrates with a metal buffer layer [1] [2]. In this study, the preparation of Pr-Fe-B thick films on glass substrates without a buffer layer was carried out. This contribution reports the evaluation on the magnetic and mechanical properties in each film with different Pr contents. Each film was deposited on a glass substrate by using a YAG pulse laser ( λ: 355 nm, frequency: 30 Hz) in the vacuum atmosphere of 2×10
^-5
Pa. The laser beam was focused on the surface of a Pr
_X
Fe
₁₄
B(X=1.8, 2.0, 2.2, 2.4) target under the deposition rate higher than 10μm/h. A pulse annealing (PA) method enabled us to crystallize hard magnetic phase. Figure 1 shows the magnetic properties as a function of Pr contents in each film thicker than 10μm. As the amount of Pr increased, coercivity increased and residual magnetic polarization decreased. We have already reported that Nd(or Pr)-Fe-B thick films with rare-earth amount less than 15 at. % deposited on Si substrates were broken after a post annealing process [3], however the Pr amounts could be reduced down to approximately 13 at. % without the deterioration of mechanical properties on glass substrates. It was also confirmed that an approximately 100μm -thick Pr-Fe-B thick film with (BH)max of about 80 kJ/m
³
could be deposited on a glass substrate.