Lowering Of Magnetic Moment Research Articles

Influence of Ti Substitution on the Critical Properties of Cu<sub>x</sub>Cr<sub>y</sub>Ti<sub>z</sub>Se<sub>4</sub> (z = 0.24 and 0.35)

Magnetization, M, and susceptibility, , measurements of CuxCryTizSe4 (z = 0.24 and 0.35) showed both strong lowering of magnetic moment in comparison with CuCr2Se4 matrix and zero-field-cooling (ZFC) – field-cooling (FC) susceptibility splitting characteristic for the spin-glass (SG) behaviour. Isothermal magnetization curves, M(H), easy saturate and large both the Curie (TC ~ 250 K) and Curie-Weiss (θCW ~ 280 K) temperatures indicate the ferromagnetic order which coexists with the SG state. The critical behaviour of polycrystalline CuxCryTizSe4 spinels investigated around the paramagnetic–ferromagnetic (PM-FM) phase transition revealed that the values of critical exponents are close to those predicted by the mean field model for long-range interactions only for Cu1.02Cr1.77Ti0.24Se4. It means that the larger spin frustration the more difficulty is it to describe the critical properties with the aid of the theoretical models.

Influence of Ce substitution on the critical properties of 3D-Heisenberg Cd x Ce y Cr2Se4 ferromagnets

The critical behaviour of single-crystalline Cd x Ce y Cr2Se4 spinels investigated around the paramagnetic–ferromagnetic phase transition revealed an increase in the critical exponents from β = 0.359, γ = 1.186, δ = 4.404 at T C = 131.95 K for Cd0.96Ce0.03Cr2Se4 to β = 0.382, γ = 1.286, δ = 4.487 at T C = 133.73 K for Cd0.83Ce0.13Cr2Se4. These values are close to those predicted by the renormalization-group calculations for a three-dimensional isotropic short-range Heisenberg ferromagnet, although their increase with the Ce substitution suggests a shift towards the mean-field estimates, characteristic of isotropic long-range exchange interactions. These results are being considered in relation to the strong lowering of magnetic moment from 5.67 µB/f.u. for y = 0.03 to 3.0 µB/f.u. for y = 0.13.

Magnetic properties of single domain ε-Fe3N synthesized by borohydride reduction route

Single domain ε-Fe3N nitride particles have been synthesized by chemical reduction followed by nitridation at 823 K. The ε-Fe3N phase crystallizes in hexagonal structure with unit cell parameters, a=2.70 Å and c=4.39 Å. There is a reduction of unpaired d electrons for intraband polarization as the nitrogen contributes to the density of states and thus results in lowering of magnetic moments. The reduction of intrinsic magnetizations and Curie temperatures with decreasing particle size is attributed to canted spin structure predominantly at the surface compared to the bulk of the particles. Chemisorption of oxygen results in the formation of oxynitride layer at the surface with a ferromagnetic coupling to the spins in the core of the particle. Mössbauer study of ε-Fe3N particles exhibits the coexistence of ferromagnetic and superparamagnetic particles and corroborates the observed magnetic properties.