Unraveling Exchange Coupling in Ferrites Nano‐Heterostructures

The magnetic coupling of a set of SrFe12O19/CoFe2O4 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 (CoFe2O4) 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 Mossbauer spectrometry, the exchange intergranular interaction is evidenced, and the critical thickness within which coupled interfaces have a uniform reversal unraveled.The magnetization reversal process of a set of nanocomposites with a local texture at the interfaces between SrFe12O19/CoFe2O4 is investigated by combining for the first time, remanence (SFD), FORCs [P(Hc)] and relaxation measurements [S(H)]. The results evidence a strong intergranular exchange coupling, and quantify the size limit of the rigid coupling regime in this kind of ferrites.image