Persisting correlation between electrical transport and magnetic dynamics in M-type hexaferrites

• Discovery of correlated activation energies governing magnetic relaxation and electrical transport in M-type hexaferrites. • Correlation persists with Aluminum substitution. • Magnetic response is similar to that of uniaxial antiferromagnets. • Correlation is interpreted as the motion of the charged magnetic domain walls that are screened by free charge carriers. In this work, we present frequency-dependent magnetic susceptibility and dc electric transport properties of three different compositions of hexaferrite Ba 1− x Pb x Fe 12− y Al y O 19 single crystals. We found a correlation between the activation energies of the dc electric transport and the ac magnetic susceptibility which persists over the whole studied range of aluminum substitution y = 0–3.3. This result is discussed in the context of charged magnetic domain walls, the pinning of which is determined by charge carriers activated across the transport gap. Our work points toward a general relaxation mechanism in ferrimagnetic semiconductors that directly affects the dynamic magnetic properties via electrical transport.