Effect of lanthanum substitution on microstructures, magnetic properties and microwave absorption properties of SrCo2Z hexaferrites

La-doped SrCo2Z hexaferrites (Sr3−xLaxCo2Fe24O41) are synthesized vis sol-gel method, and then the microstructure, magnetic properties and microwave absorption properties are investigated in detail. All results indicated that La elements are successfully doped into SrCo2Z hexaferrites and hardly affects the phase structures. While the magnetic performance is greatly improved through La-doping, Ms and Hc both increases with the increasing La-doping content due to Fe3+-O-Fe2+ super-exchange interaction in the hyperfield at 12 k and 2b sites. Furthermore, the microwave absorption properties of Sr3−xLaxCo2Fe24O41 hexaferrites could also be improved by La-doping. Sr2.9La0.1Co2Fe24O41 hexaferrites with the thickness of 4.5 mm exhibit the best microwave absorption performance with the minimum RL value of − 47.70 dB at 5.92 GHz. The double absorption peaks are observed for the thicker samples, which could increase the effective absorption broadband of Sr3−xLaxCo2Fe24O41 hexaferrites. Finally, the physical mechanism for microwave absorption of Sr3−xLaxCo2Fe24O41 hexaferrites is proposed according to wavelength and impedance matching models.