Structure and magnetic properties of W-type hexaferrites

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• W-type hexaferrites (WHFs) are hard magnetic materials with potential for permanent magnets.
• Their large crystalline anisotropy and cation tunability are advantageous.
• Complex structural and magnetic characteristics require further investigation.

Purpose of the Study:

• To investigate the substitution of metals (Mg, Co, Ni, Zn) in W-type hexaferrites.
• To elucidate the crystal and magnetic structures of these substituted WHFs.
• To understand the relationship between cation substitution and magnetic properties.

Main Methods:

• Combined refinements of X-ray and neutron powder diffraction data.
• Determination of atomic positions and magnetic dipolar moments.
• Macromagnetic property measurements using a vibration sample magnetometer.

Main Results:

• All four types of WHFs exhibit ferrimagnetic ordering.
• Mg, Ni, and Zn substituted WHFs show collinear magnetic ordering along the c-axis.
• SrCo$_{2}$Fe$_{16}$O$_{27}$ displays a transition from uniaxial to planar magnetic ordering in the ab-plane.
• Measured saturation magnetization (M$_{s}$) correlates well with calculated M$_{s}$ from diffraction data.

Conclusions:

• The study successfully determined the atomic and magnetic structures of substituted WHFs.
• Metal substitution significantly impacts magnetic ordering, offering tunability for applications.
• The Rietveld model used is robust, validated by the agreement between measured and calculated M$_{s}$.