Adjusting the magnetic properties of Ni<inf>0.5</inf>Zn<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> thin film for high frequency applications by introducing Fe<inf>65</inf>Co<inf>35</inf> alloy nanoclusters

Abstract

I . INTRODUCTIONRecently, duo to the growing pursuits for miniaturization and steadily increasing operating frequency into the gigahertz (GHz) range of electromagnetic devices, materials with high resistivity, high saturation magnetization and high resonance frequency have become consuming all-important . The soft magnetic ferrite thin films, such as NiZn ferrite thin films which have high resistivity, are supposed to be a promising material for high frequency applications [1,2] . However, these ferrite thin films cannot keep high permeability in the GHz frequency range due to their low saturation magnetization . Therefore, much effort has been focused into improving their magnetic properties . It is considered that "nanocomposite systems" play an important role in optimizing the magnetic properties of NiZn ferrite [3][4] . However, it is difficult to prepare the above-mentioned nanocluster-matrix dualistic magnetic nanocomposite film by traditional magnetron co-sputtering deposition method . For example, when NiZn ferrite target and a Fe-Co alloy target are used to prepare a composite film via a co-sputtering process, Fe and Co atoms sputtered from alloy target and Fe, Ni, Zn atoms sputtered from NiZn ferrite target tend to form a new type of ferrite film whose composition will be different from that of original NiZn ferrite target rather than forming the designed nanocluster-matrix dualistic magnetic nanocomposite film . Different from the traditional magnetron co-sputtering deposition method, in this work, a new preparation method ( Fig . 1) was developed to in situ assembly of nanocluster-matrix binary magnetic nanocomposite films, in which the Fe 65 Co 35 alloy nanoclusters prepared by plasma-gas-condensation nanocluster beam deposition method were encapsulated into Ni 0 .5 Zn 0 .5 Fe 2 O 4 thin films fabricated via radio frequency magnetron sputtering . The structure and magnetic properties of the composite films have been investigated systematically by using TEM, SEM, XRD, XPS, and VSM . II . RESULT AND DISCUSSION In this work, initial Fe 65 Co 35 nanoclusters with the mean cluster diameter of d = 6 nm were used . TEM and SEM observations indicate that the (Fe 65 Co 35 ) x @(Ni 0 .5 Zn 0 .5 Fe 2 O 4 ) 100-x nanocomposite films obtained have a clear polycrystalline structure . The XPS results indicate that the nanocomposite film is composed by the NiZn-ferrite thin film and metallic Co and Fe that come from the Fe 65 Co 35 alloy nanoclusters . The influences of x on resistivity (ρ), saturation magnetization (M s ) and coercivity (H c ) of the composite films are shown in Fig . 2 . As shown in Fig . 2(a), with the increase of x the ρ decreases monotonically . It should be note that although the ρ of x=3 .1 is about triple that of x=51, the ρ of the composite films still maintain at a high value (~10 9 mΩ cm) at x=51 . As shown in Fig . 2(b), the M s of the composite films increases from about 28 emu/cm 3 (x=0) to 264 emu/cm 3 (x=51) . The increased M s should attribute to the introduction of Fe 65 Co 35 allo...

Influence of Zn+2 Doping on Ni-Based Nanoferrites; (Ni1−x ZnxFe2O4)

“…Different ferrite systems such as Mn–Zn, Ni–Zn, or Mg–Mn are very significant for high-tech applications [27,28,29]. Ni–Zn bulk ferrite nanomaterials are the only core materials applicable to high-frequency applications [27,30,31]. The main drawback is that its performance is constrained to 100 MHz due to eddy current at high frequencies.…”