Controlling magnetic coupling in bi-magnetic nanocomposites

Abstract

Correlation between synthesis technique, resulting in different levels of particle agglomeration at the microscopic scale, and magnetic coupling in nanocomposites.

Tuning the Magnetic Properties of Hard–Soft SrFe12O19/CoFe2O4 Nanostructures via Composition/Interphase Coupling

“…To clarify the relationship between the morphostructural features and interface magnetic coupling, field-dependent magnetization loops recorded at 300 K for NC_2, NC_5, SFO, and CFO are reported in Figure a. All the curves exhibit a single reversal process of magnetization, suggesting that the two magnetic phases are homogeneously dispersed and strongly magnetically coupled , because of the efficiency of the one-pot sol–gel method. , The corresponding magnetization loops of all the NCs are included in Figure S8. The NCs show an intermediate magnetic behavior between the two individual phases, as proved by the comparison of the parameters reported in Table .…”

“…This scenario has stimulated an intense activity for the quest of new nanomaterials, as well as the enhancement of the properties of materials currently used, with a reduced or even zero content of REEs . In this regard, ferrites have shown to be a promising class of materials, in particular M-type SrFe 12 O 19 magnets, which show the best magnetic performance among ferrites (energy products of 40–460 kJ m –3 ). , Many synthesis procedures have been investigated as a potential strategy to develop nanostructured ferrites through different bottom-up approaches. ,− In this regard, among the diversified ways investigated so far, exchange coupled hard/soft nanocomposites (NCs) have received significant attention. , Our recent studies on magnetic NCs clearly show that the synthesis strategy plays a critical role in the extent of magnetic coupling that can be achieved between the phases. − This strongly depends on many parameters, such as the degree of particle agglomeration of each individual phase and specifically the nature of the interface, which must be optimized to obtain a maximum interfacial contact. To achieve high performances, PMs ideally require a squared magnetization loop to keep as much of the magnetization as possible within the magnet: specifically, a strong saturation magnetization ( M S ) together with a high remanent magnetization ( M R ) combined with a high coercivity ( H C ) (i.e., high resistance to demagnetization). , Despite considerable efforts, usually all these values cannot be maximized simultaneously in the same material.…”

“…Nevertheless, the lack of comprehensive studies on the degree of magnetic coupling in such systems is rather broad. In this regard, we have recently investigated the role of synthesis strategy in controlling the magnetic coupling of bimagnetic systems. , In this paper we report an extensive investigation on various SrFe 12 O 19 /CoFe 2 O 4 (SFO/CFO) NCs covering a range of compositions, which were synthesized through a one-step combustion sol–gel approach, adapted from our previous strategies . They consist of a hard-magnetic phase SFO, with a high magnetocrystalline anisotropy constant ( K = 0.35 MJ/m 3 ) and high magnetic uniaxial anisotropy along the c -axis, , and a soft phase CFO, with a higher M S (0.45 MA/m) .…”

Combined Bottom-Up and Top-Down Approach for Highly Ordered One-Dimensional Composite Nanostructures for Spin Insulatronics

“…In such a case, where exchange bias measurements do not give much information, it is worthwhile to probe the magnetic coupling between the two phases using other methods. To probe the extent of magnetic coupling in composite materials, direct current demagnetization (DCD) experiments have been established to be a quick, easy, and reliable way. ,,− Earlier, we performed DCD experiments on continuous composite films and found a strong coupling between the two magnetic phases in such films . However, because the nanowire samples were fabricated using a top-down approach, it is necessary to check the quality (in particular, the coupling between the two magnetic phases) postfabrication.…”

“…This results in a tailor-made end material that can be engineered for specific applications via introducing a wide variety of correlated phenomena. Magnetic oxides and their composites are thus being explored extensively, both with regard to making innovations in the synthesis techniques − as well as efforts toward mimicking and/or improving on single-phase behavior in these biphasic compounds. − Composite thin films and heterostructures have also been fabricated − to broaden the prospects for applications.…”