The characterization of barium hexaferrite thin-films at microwave frequencies is important for determining their electromagnetic properties by measuring the elements of the permeability tensor. Layers of 15 µm were deposited by RF sputtering on a coplanar line. As a result of this deposition and annealing technique, the magnetic moments are mainly oriented in the plane of the layer. By measuring the S parameters under magnetic field conditions, the µ and κ elements of the permeability tensor were extracted and their variations as a function of the applied field were highlighted. Possible applications to absorbent layers are being considered.