Hard magnetic property improvement of sputter-prepared FePd films on glass substrates by underlayering with refractory Nb, Mo, and W elements

Magnetic properties and structure of sputter-prepared FePd thin films on the glass substrates by underlayering with refractory elements M (M= Nb, Mo, and W) have been studied. The structural analysis shows that FePd films have a (111) preferred orientation. All studied FePd films exhibit in-plane magnetic anisotropy. For single-layer FePd films, the coercivity (Hc) and magnetic energy product ((BH)max) are increased with annealing temperature (Ta) and reached the maximum value of 1.3 kOe and 3.8 MGOe in the sample annealing at 600 oC. With further increase of Ta, magnetic properties drop rapidly. Dependence of magnetic hardening on Ta can be explained by dominant solid reactions in different region of Ta including ordering and grain growth. Interestingly, magnetic properties of L10-FePd are largely improved by underlayering with 5-nm-thick Nb, Mo, and W layers. Both the coercivity and energy product are significantly increased to 1.6 kOe and 4.9 MGOe for M = Nb, 2.5 kOe and 6.4 MGOe for M = Mo, and 3.3 kOe and 8.7 MGOe for M = W, respectively. Structural analysis suggest that this magnetic enhancement is related to both higher ordering degree and refined microstructure.