ABSTRACT
Hard-soft nanocomposites of (1 -x) BaFe12O19/x(Zn0.5Co0.5)Fe2O4, forx= 0.00, 0.25, 0.50, 0.75 and 1.00, were prepared via co-precipitation and high-speed ball milling techniques, respectively. The synthesized samples were characterized via x-ray diffraction, transmission electron microscope, Fourier transform infrared (FTIR), and vibrating sample magnetometer. XRD revealed the formation of hard-soft nanocomposites. TEM indicated that the two phases are well distributed and the particle size distribution is narrower for low content of soft phase, leading to better exchange coupling between the grains. Magnetic measurements were performed at 300 K and 77 K. The results showed a good single-phase magnetic behavior, verifying the good exchange coupling between hard and soft phases. For low (Zn0.5Co0.5)Fe2O4content, the dipolar interactions were dominated by the exchange-coupling interactions. Additionally, the optimum values of saturation and remanent magnetizations, coercivity, and squareness ratio were obtained forx= 0.5. This was attributed to the dominance of exchange-coupling interaction. The enhancement of magnetic properties and energy product (BH)maxfor nanocomposites at low temperature is skilled in the reduction of the thermal fluxes of magnetic moments at the surface. The maximum energy product (BH)maxwas observed in C2 at both temperatures with a smaller value than that of pure BaFe12O19.
ABSTRACT
In spin valve type systems, one ferromagnetic electrode must be magnetically hard to act as a reference layer while the other electrode must be magnetically soft to act as a sensor or storage layer. This magnetic hard-soft architecture can usually be obtained by four different methods: the use of two ferromagnets with different coercive fields (here CoFe(2) and Ni(80)Fe(20)), the use of an underlayer enhancing the coercive field of one of the two ferromagnets (here Ta and Ru), the use of a ferromagnet coupled to a ferrimagnet or antiferromagnet (here NiO/CoFe(2) and CoFe(2)O(4)/CoFe(2)), or the use of an artificial antiferromagnet (here CoFe(2)/Ru/CoFe(2)). We show that at least the first and the third methods seem to work with pulsed laser deposition in the thermodynamic conditions used.
