Unraveling Exchange Coupling in Ferrites Nano-Heterostructures.

The magnetic coupling of a set of SrFe 12 O 19 /CoFe 2 O 4 nanocomposites is investigated. Advanced electron microscopy evidences the structural coherence and texture at the interfaces of the nanostructures. The fraction of the lower anisotropy phase (CoFe 2 O 4 ) is tuned to assess the limits that define magnetically exchange-coupled interfaces by performing magnetic remanence, first-order reversal curves (FORCs), and relaxation measurements. By combining these magnetometry techniques and the structural and morphological information from X-ray diffraction, electron microscopy, and Mössbauer spectrometry, the exchange intergranular interaction is evidenced, and the critical thickness within which coupled interfaces have a uniform reversal unraveled.