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

Structural, electronic and magnetic properties of Fe2-based full Heusler alloys: A first principle study

In this study, physical properties of half Heusler (HH) alloys LiCrZ (Z = P, As, Bi, Sb) are explored using Wien2k package. All these alloys are found to be the most stable with Type-1 configuration. Furthermore, ferro-magnetic (FM), anti-ferromagnetic (AFM) and non-magnetic (NM) calculations are performed to obtain the most stable magnetic phase using Type-1 configuration and all compounds are found stable in FM phase. The calculated formation energy has also predicted that these alloys are stable. The LiCrBi and LiCrSb alloys showed 100% spin polarization and half metallic character. The calculated magnetic moment is 4 μB and band gap for LiCrBi and LiCrSb is 1.8 eV. The spin polarized density of states (DOS) have also been calculated and discussed. The effect of pressure on band gap has also been investigated. The increase in band gap and decrease in lattice constant with the increase of applied pressure have been observed and explained in detail. In order to check the mechanical stability, elastic constants are constants are calculated and all compounds are ductile. The predicted results of HH alloys will be useful for spintronics applications.

Theoretical investigation of structural, magnetic and elastic properties of half Heusler LiCrZ (Z = P, As, Bi, Sb) alloys

Twins – A weak link in the magnetic hardening of ThMn12-type permanent magnets

Half metallic ferromagnetism in Ni based half Heusler alloys

First principles calculation of elastic and magnetic properties of Cr-based full-Heusler alloys

First-principles study of magnetic, electronic, elastic and thermal properties of GdFe2

A first-principles study of elastic, magnetic, and structural properties of PrX2 (X=Fe, Mn, Co) compounds

The structural, electronic, magnetic and elastic properties of half-Heusler alloys PtMnSb, PtVSb, PtCrSb and PtCoSb are investigated using first-principles calculation based on Density Functional Theory DFT. The Full Potential local Orbital (FPLO) method, within the General Gradient Approximation (GGA) and Local Spin Density Approximation (LSDA), have been used. The calculated structural, electronic and magnetic properties are in good agreement with available experimental and theoretical data. Using GGA approximation, only PtVSb shows a half-metallic behavior with a spin-down band gap and total magnetic moment of 0.802 eV and 2 µ B respectively. Both of PtVSb and PtMnSb alloys are half-metallic with spin-down band gaps of 0.925 eV and 0.832 eV and magnetic moments of 2 µ B and 4 µ B respectively using LSDA approximation. The bulk modulus and its first pressure-derivative of these alloys are calculated using the modified Birch–Murnaghan equation of state (EOS). The effect of pressure on the lattice constant, energy gap and bulk modulus is investigated. Under pressure, PtMnSb and PtCrSb turn into half-metallic alloys at nearly 6 GPa and 27 GPa respectively using GGA approximation.

Samy H. Aly

Papers

First principles calculation of elastic and magnetic properties of Cr-based full-Heusler alloys

First-principles study of magnetic, electronic, elastic and thermal properties of GdFe2

A first-principles study of elastic, magnetic, and structural properties of PrX2 (X=Fe, Mn, Co) compounds

Investigating half-metallicity in PtXSb alloys (X=V, Mn, Cr, Co) at ambient and high pressure

A molecular-field study on the magnetocaloric effect in Er2Fe17