High-coercivity, c-axis oriented Nd2Fe14B films grown by molecular beam epitaxy

Abstract

Thin films of Nd2Fe14B with a c-axis orientation and bulklike magnetic properties have been grown via molecular beam epitaxy with thicknesses as low as 300 Å. The films are grown on single-crystal MgO(100) wafers overcoated with epitaxial Mo(100) buffer layers. The 2–14–1 phase is crystallized either by sequential deposition or codeposition of Fe, Nd, and B from pure elemental evaporation sources onto 600–700 °C substrates. The structure of each film was characterized in situ with reflection high-energy electron diffraction and ex situ with x-ray diffraction. For the sequentially deposited films, the in-plane saturation field is 60–70 kOe at 300 K, consistent with the bulk anisotropy field of 73 kOe. The spin–reorientation transition at 135 K can also be clearly seen in the in-plane and out-of-plane magnetization versus temperature data. The out-of-plane coercivities typically range from 15 to 20 kOe at 20 K, and from 3 to 8 kOe at 300 K. Codeposition results in a multiphase structure, with Nd2Fe14B show the minority phase. The multiphase structure results in reduced perpendicular anisotropy.