Magnetron Sputtered Perpendicular Barium Hexaferrite Thin Films Produced by the Multilayered Method

Abstract

We report on the synthesis and characterization of thin M-type barium hexaferrite (BaFe12O19 or BaM) films on sapphire (0001) substrates by RF magnetron sputtering. Single layers of 150 nm, 200 nm (S200), 400 nm (S400), 600 nm, and 700 nm were fabricated. Multilayered technique with inner-layer annealing was employed to fabricate the 400 nm (M400) BaM films. The thickness dependence of the magnetic, structural, elemental analysis, and surface morphological properties of the BaM films has been investigated using VSM, XRD, EDX, and SEM, respectively. For the M400 BaM films, excellent magnetic properties with high values of out-of-plane coercivity (Hc┴ = 3.1 KOe) and squareness (S┴ = 0.9) were obtained. The surface morphology of the M400 shows a platelet-like grains, which have their c-axis orientation in the out-of-plane direction. The magnetic properties and XRD data of the S200 films and M400 were about the same. For the single S400, S600, and S700 films, the magnetic properties have been reduced due to the excess oxygen concentration and the exchange interactions, the stress relaxation of the lattice constant, and the formation of the acicular grains. The acicular grains of the S400 films favor their c-axis aligned in the in-plane direction.