Selective 2p-3d electron orbits exchange coupling in amorphous rare earth-transition metal-boron alloys

One of the major bottlenecks in amorphous light rare earth-transition metal (LRE-TM) alloy films for magneto-optic (MO) recording media in blue wavelengths (~400 nm) is the large demagnetization energy (E_D), which originates from shape anisotropy of the samples and decreases the effective magnetic anisotropy energy K_Ueff perpendicular to the film planes. The reduction of this demagnetization energy and enhancement of polar Kerr rotation angles (θ_K) are attempted by the addition of boron (B) into the amorphous LRE-TM films, such as amorphous (NdFe)_100-XB_X films. The additive B plays the role of reducing an Fe sub-magnetic moment by selective 2p-3d electron orbits exchange coupling (SEC) between B and Fe. The SEC results in the reduction of E_D, enhancement of K_Ueff and increase of θ_K in the amorphous (NdFe)_100-XB_X alloy films