Magnetic, Mössbauer, and neutron diffraction investigations of W-type hexaferrite BaZn2−xCoxFe16O27 single crystals

Abstract

Macroscopic magnetic measurements, Mössbauer, and neutron diffraction studies have been carried out on BaCoxZn2−xFe16O27 [(Zn−Co)2-W] single-crystal hexaferrites. The extrapolated saturation magnetization values σs(0) are slightly lower than those found in the literature. Such differences have been justified as due to the different Co and Zn distributions among the tetrahedral sites.The Co ions induce a strong planar contribution to the magnetic anisotropy. At low temperature, the spin order, found from the macroscopic magnetic measurements and preliminary neutron diffraction studies, is planar, while the Mössbauer data indicate a conical order with an angle of 70° with respect to the c axis. By increasing the temperature, the cobalt anisotropy decreases and a spin reorientation to easy axis is observed.

Synthesis of nanocrystalline Ba(CoxZn1−x)2Fe16O27 by sol–gel auto-combustion method

“…The Ba(Co x Zn 1−x ) 2 Fe 16 O 27 hexaferrite powders are obtained at the calcinations temperature of 900 • C. The M s shows a slightly maximum at X = 0.5, which agrees with the results in the results in Ref. [5,15]. The H c curve shows its minimum at X = 0.5-0.75, revealing a transition from uniaxial (X = 0) to planar anisotropy (X = 1).…”

Microwave ferrites, part 1: fundamental properties

“…158 In other words, Co substitution modifies the anisotropy, changing it from c-axis to c-plane. 144,159 As an example, Li et al 24 This deviation of the magnetic moments from the c-axis, however, occurred at a much lower temperature of 50 K for Sr 3 Z. This dependence of moment direction was explained by disappearance of effective moments of cobalt ions in these temperature regions.…”

Structure parameters and magnetic properties of Me2W1 cobalt-containing hexaferrite systems synthesized by the SHS method

“…It is natural that with increasing cobalt ion content, the spin reorientation phase transition from EMD to EMP type anisotropy will be observed in solid solutions of the Co 2+ -containing hexaferrites combined with any of the above-listed ions. We note that these transitions are observed not only for concentration but also for temperature changes [2][3][4]. Neutron-diffraction investigations of Co 2-x Zn x W system hexaferrites carried out in [3] have demonstrated that the EMD ↔ EMP temperature spin reorientation transition proceeds through the easy magnetization cone (EMC) phase.…”

“…The Co 2 W hexaferrite has anisotropy of the easy magnetization plane (EMP) type and the anisotropy field relative to the hexagonal axis exceeding -20 kOe at room temperature [1,2]. The minus sign hereinafter means the EMP-type anisotropy.…”