Dependence of pulsed-laser deposition parameters on the microstructure and magnetic property of Nd-Fe-B thin films grown at high substrate temperature

We systematically studied the dependencies of substrate temperature, laser fluence, deposition time, ambient gas pressure and laser frequency on the structural and magnetic properties of Nd-Fe-B thin films synthesized by pulsed-laser deposition at high substrate temperature T _s. A coercive force of 2.0-2.4 kOe was obtained on samples with a thickness of 70-90 nm and an average grain size of 50-70 nm grown at T _s of 620-650°C. We showed a clear trend through statistical analysis that the coercivity decreases with increasing film thickness up to 800 nm due to an increase in the crystalline grain size. Oxidation layer and defects on the grain surface may also have greatly reduced the nucleation field and thus resulted in a low coercivity and low saturation magnetization of the samples. Comparison of the films made by PLD and sputtering under similar conditions has been discussed.