Influence of Co Doping on Structural and Magnetic Properties of Fe<sub>2</sub>P

Abstract

The aim of this article is to provide an overview on the effect of Co doping for Fe in Fe2P on the lattice parameters, magnetic transition point, saturation magnetic moment, paramagnetic Curie point and paramagnetic moment. Five alloys in the series (Fe1-xCox)2P (x= 0.03, 0.10, 0.30, 0.50, 0.70) were synthesized and investigated using X-ray diffraction, magnetization and paramagnetic susceptibility measurements. Alloys with x=0.03 and 0.10 crystallize in Fe2P type hexagonal structure while those for x= 0.30, 0.50, 0.70 crystallize in Co2P type orthorhombic structure. In the hexagonal phase, the substitution of Co for Fe leads to a very little enhancement in the unit cell volume but in the orthorhombic phase the increase in Co concentration leads to monotonic decrease in the unit cell volume. All the five alloys are ferromagnetically ordered and  display nonlinearity in the -1-T curves above Tc. Interestingly, the compounds for x= 0.10, 0.30 and 0.50 shows a sharp first order type ferromagnetic to paramagnetic phase transition. The paramagnetic Curie temperature (θP) increases up to x=0.50. The saturation magnetizations and paramagnetic moments monotonically decrease with the increase in the Co concentration. Both Ni and Co substitution for Fe in Fe2P are known to strengthen the ferromagnetic ordering, however, the effect of Co substitution has stronger influence on the structural parameters and magnetic properties than the Ni. The observed nonlinearity in the -1-T curves above Tc and the Rhodes- Wohlfarth ratio (μP/μs) greater than one, gives a clear evidence of presence of large magnetic correlations far above Tc and itinerant magnetism in these compounds.