Structural, dielectric and magnetic properties of Cr–Zn doped strontium hexa-ferrites for high frequency applications

Structural, magnetic and microwave absorption properties of doped Ba-hexaferrite nanoparticles synthesized by co-precipitation method

“…7, the magnetic characteristics of the doped BaM ferrites are significantly influenced by the substitution of Fe þ 3 ions by Zn þ 2 , Co þ 2 and Zr þ 4 cations and can be explained according to which of the five different lattice sites are occupied by the magnetic and nonmagnetic ions of Co þ 2 , Zn þ 2 and Zr þ 4 . It was reported that Co þ 2 cations with the magnetic moment of 3 B μ occupy both 2b and 4f 2 positions, while the nonmagnetic Zn þ 2 cations have a great preference for occupying 4f 1 sites [19][20][21]. It is also known that the nonmagnetic Zr þ 4 cations are replaced by Fe þ 3 ions at the 2b sites for small number of substitutions (x≤0.1), and at the 4f 1 for higher numbers of substitutions [20].…”

“…The increase in the saturation magnetization above x ¼0.4 may be related to the presence of higher concentration of nonmagnetic Zn þ 2 and Zr þ 4 cations on the 4f 1 sites. However, for a better understanding of the site occupancy of each ion, mössbauer spectroscopy is required [19][20][21]. The variation of coercivity (H c ) of the doped Ba-hexaferrites as a function of x are also shown in Fig.…”

Fabrication, structural, dielectric and magnetic properties of tantalum and potassium doped M-type strontium calcium hexaferrites

“…It is observed from the figure that the AC conductivity slightly increases with frequency upto 1.53-1.82 GHz above which relaxation behavior is demonstrated. This may be explained in a way that at lower frequencies, the hopping of electrons between Fe 2+ and Fe 3+ is less but as frequency increases, the jumping of electrons is increased and conductivity is also increased [36]. It may be attributed that as compared to the activation of wide-ranging diffusive conduction, only a fraction of energy is required for the hopping (backward and forward) of the electrons [37].…”

Novel approach for designing a thin and broadband microwave absorber in Ku band based on substituted M-hexaferrites

“…Many studies have been performed to modify the magnetic properties of barium hexaferrite by substitution of Fe 3+ ions with various ions such as Cr-Zn [8], Co [9], Ce-Co [10], Co-Ti [11], La-Co [12], La-Ce-Zn [13], Zr-Cu [14] etc. However, the design of novel microwave absorbers with broad bandwidth, high reflection loss and thin thickness is still challenging.…”

“…Saturation magnetization is severely dependent on the super-exchange interactions between 4f 1 -12k and 4f 1 -2a which are very sensitive to interatomic distances. Generally substitution by different cations8 with higher ionic radius than Fe 3+ ions leads to diminish the super-exchange interactions and thereby the occurrence of reduction in saturation magnetization. In the M-type barium hexaferrite Fe 3+ ions have been distributed on five different sub-lattices which are divided into up spin (12k,2a,2b) and down spin (4f 1 ,4f 2 ) sites.…”