Magnetic property tuning of epitaxial spinel ferrite thin films by strain and composition modulation

Epitaxial spinel ferrite CoFe 2 O 4 and NiFe 2 O 4 thin films and bilayers of NiFe 2 O 4 and CoFe 2 O 4 have been grown by pulsed laser deposition on (001)-oriented SrTiO 3 and MgO substrates. Both the single layer thin films showed epitaxial growth on MgO substrates with out-of-plane magnetic easy axis, originating from the out-of-plane compressive strain and negative magnetostriction constant. However, films on SrTiO 3 substrates exhibited a magnetic easy axis along the in-plane. Magnetic hysteresis loops showed intermediate shape between magnetically hard CoFe 2 O 4 and magnetically soft NiFe 2 O 4 without two-step switching. Interdiffusion between spinel phases was suppressed using a blocking layer of MgO.