Magnetic X-ray Spectroscopy Studies of PLD grown Magnetoelectric Hexaferrites

The work here in was undertaken with two main objectives. The first has been to design and develop a bespoke pulsed laser deposition growth system to enable the growth of high quality transition metal oxide thin films. The system has been constructed to allow for the growth of multi-block or layered systems, such as the R, S and T-blocks of hexaferrites, by utilising an alternating target approach. Ultimately, the growth system’s ability to grow complex oxide thin films has been tested and the successful growth of an epitaxial M-type hexaferrite, with material properties that compare well to the literature, has been realised. Additionally, the magnetoelectric effect in M-type Ti-Co doped strontium hexaferrite, SrCo2Ti2Fe8O19, has been studied using a combination of magnetometry and element specific soft x-ray spectroscopies. A large increase (>30x) in the magnetoelectric coefficient is found when Co2+ enters the trigonal bi-pyramidal site. The 5-fold trigonal bi-pyramidal site has been shown to provide an unusual mechanism for electric polarization based on the displacement of magnetic transition metal ions. For Co entering this site, an off-centre displacement of the cation may induce a large local electric dipole as well as providing an increased magnetostriction enhancing the magnetoelectric effect.