Microstructures and properties of high-entropy alloys

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Hexagonal ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics

Magnetocaloric effect: From materials research to refrigeration devices

Magnetic Relaxation in Fine‐Particle Systems

Neutron diffraction studies of some hexagonal ferrites: BaFe12O19, BaMg2W and BaCo2W

The authors present results obtained by 57Fe Mossbauer spectroscopy on R2Fe14B, where R represents any of the rare earth elements except Pm, Eu and Yb. Additional measurements have been performed on oriented powder for R=Y, Pr and Ho. For the case of Y the measurements at 4.2 K were performed in applied magnetic fields up to 4 T. From these measurements it is deduced that the only compounds with an easy c axis at room temperature which show a spin reorientation of the iron sublattice at a lower temperature are the Nd and Ho alloys. Iron hyperfine fields are anisotropic and the anisotropy has different signs on different sites. An analysis of the non-4f contribution to the electric field gradient at the 161Dy or 166Er nuclei in Dy2Fe14B and Er2Fe14B is consistent with published results on 155Gd in Gd2Fe14B. In order to explain that a spin rotation is found only for R=Nd, Ho the authors invoke the relative small quadrupole moment of the 4f shell for these two ions and crystal field terms of higher than second order.

https://iopscience.iop.org/article/10.1088/0305-4608/17/2/017/pdf

Mössbauer spectroscopy of R2Fe14B

Neutron diffraction study of LaFe11.31Si1.69 and LaFe11.31Si1.69H1.45 compounds

The structural and magnetic characteristics of RE 2 Fe 14 BH x hydrides with RE ≡ Y, Ce, Er have been studied as a function of x . Both Curie temperature and magnetization are increased on hydriding the ternary bondes. Neutron diffraction experiments performed on deuterated samples have permitted the location of the host sites and the measurement of the magnetic moments of iron and RE. Different anomalies reported in the structural and magnetic behaviour of Ce 2 Fe 14 BH x are related to the change of electronic state on cerium.

Pierre Wolfers

Papers

Neutron diffraction studies of some hexagonal ferrites: BaFe12O19, BaMg2W and BaCo2W

Mössbauer spectroscopy of R2Fe14B

Neutron diffraction study of LaFe11.31Si1.69 and LaFe11.31Si1.69H1.45 compounds

Structural and magnetic properties of RE2Fe14BH(D)x; REY, Ce, Er

Electronic structure and stability of new FCC magnesium hydrides Mg7MH16 and Mg6MH16 (M = Ti, V, Nb): An ab initio study