The key for the existence of magnetic induced reorientation is strong magnetocrystalline anisotropy, i.e., the coupling between ferroelastic and ferromagnetic ordering. To increase the transformation temperatures and thus functionality, various elemental alloying in Ni-Mn-Ga is tried. We analyzed more than twenty polycrystalline alloys alloyed by small amount (up to 5atom%) of transitional metals Co, Fe, Ni, and Cu for the value of magnetic anisotropy in search of general trends with alloying. In agreement with previous reports, we found that maximum anisotropy occurs at stoichiometric Ni2MnGa and any alloying decreases its value. The strongest decrease of the anisotropy is observed in the case where the alloyed elements substitute Ga.
In recent years, nanosized spinel-type ferrites emerged as an important class of nanomaterials due to their high electrical resistivity, low eddy current loss, structural stability, large permeability at high frequency, high coercivity, high cubic magnetocrystalline anisotropy, good mechanical hardness, and chemical stability [...]
Abstract
FeSi films with different substrate temperature (Ts) were deposited on MgO (001) substrates by a radio frequency magnetron sputtering. During the change of crystal structure from amorphous epitaxial state, magnetic anisotropy experienced three stages: dominant uniaxial magnetic anisotropy (Ts < 400 ℃) and enhanced cubic magnetocrystalline anisotropy (400 ℃ £ Ts £ 600 ℃) and weak cubic magnetocrystalline anisotropy (Ts = 700 ℃ and 800 ℃). In addition, resonance frequency ƒr firstly decreases, then reaches the maximum value, and finally disappears due to the large coercivity field. These results demonstrate the correlation between the structure, static, dynamic magnetic properties of FeSi films, and provide an effective method to prepare soft films with deterministic uniaxial or cubic magnetic anisotropy for practical application.
Mn–Ti, Zn–Ti, Zn–Zr substituted M-type Sr-hexaferrites (SrM), SrFe12−2xM1xM2xO19 (0 ≤ x ≤ 2.0, M1 = Mn or Zn; M2 = Ti or Zr) were synthesized, and their solubility, crystalline structure, and high-frequency properties were studied. Zn–Zr substitution caused a relatively large lattice parameter change and resulted in lower solubility (x ≤ 1.0) in the M-type phase compared with Mn–Ti and Zn–Ti substitutions. However, the ferromagnetic resonance frequency (fFMR) effectively decreased with increasing x in SrFe12−2xZnxZrxO19 (Zn–Zr:SrM) (0 ≤ x ≤ 1.0) and the electromagnetic wave (EM) absorption frequency also varied according to the shift in fFMR in the 7–18 GHz range. This is attributed to a gradual decrease in the magnetocrystalline anisotropy of Zn–Zr:SrM (0 ≤ x ≤ 1.0) with an increase in x. Zn–Zr:SrM (x = 0.9)–epoxy(10 wt%) composites exhibited a high EM absorption in the X-band (8–12 GHz) with the lowest reflection loss of <−45 dB. The sample with x = 0.8 showed a broad Ku band (12–18 GHz) absorption performance satisfying RL <−19 dB at 11 ≤ f ≤ 18 GHz.
Compositional Dependence of Magnetocrystalline Anisotropy in Fe-, Co-, and Cu-Alloyed Ni-Mn-Ga