Nickel and copper substitution in Zn2-W

With the aim of better understanding the role of divalent metal cations in the W-type hexagonal ferrites we have carried out a complete magnetic and Mössbauer characterization of the two series (Zn,Cu)2-W and (Zn,Ni)2-W. The main results are: a) like zinc, copper and nickel ions enter the S-block, but prefer the octahedral coordination; b) in analogy with cubic ferrites, the effects of copper substitution on the magnetic properties are dependent on the thermal history of the samples; c) the possibility of improving Zn2-W as permanent magnet material by copper substitution is confirmed.