The effects of Nd2Fe14B grain size and Nd coating on the coercivity in sputter-deposited Nd-Fe-B/Nd thin films have been investigated in order to gain an insight into the coercivity mechanism of Nd-Fe-B magnets. Highly textured Nd2Fe14B particles were grown successfully on the MgO(100) single-crystal substrate with the Mo underlayer. As the Nd-Fe-B layer thickness tNFB was decreased from 70 to 5 nm, the coercivity Hc increased gradually from 6.5 to 16 kOe. By depositing the Nd overlayer onto these films and post-annealing at 500 °C, the Hc value further increased from 17.5 kOe (tNFB=70 nm) to 26.2 kOe (tNFB=5 nm). The amount of Hc increase by the combination of the Nd coating and post-annealing was about 10 kOe irrespective of the tNFB value. These results therefore suggest an independence of size and interface effects on the coercivity of Nd-Fe-B magnets.
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