ИСТИНА

In the present work we have investigated magnetic field dependences of magnetization (T=2.0-70 K, B≤7.5 T) in Pb1-yFeyTe alloys synthesized by the Bridgman method. A single-crystal Pb1-yFeyTe (y=0.02) ingot was cut perpendicular to the growth axis into disks with various impurity content. The main objectives were to study the kinetics of change of the concentrations of magnetic ions in different magnetic states when doping, the contribution of clusters of iron ions to magnetic properties and determination of their basic parameters. Obtained experimental results allow us to conclude that the magnetization M of Pb1-yFeyTe alloys contains five principle contributions: Brillouin paramagnetism of isolated iron ions MBr, temperature independent and linear in magnetic field contribution M0, including obviously diamagnetic contribution of the host lattice and diamagnetic and paramagnetic contributions of free holes, ferromagnetic contribution of clusters of iron ions Mc and oscillating share of de Haas–van Alphen effect. Successive separation of these contributions is performed. Approximations of M–Mc–M0 (B) and Mc(B) dependences by the Brillouin functions allow us to determine the main magnetic parameters of isolated iron ions in different magnetic states and of ferromagnetic clusters in alloys. It is shown that the total concentration of magnetically active iron ions in different magnetic states NFe, that does not exceed 0.1 mol.%, the concentration Nc and average spin Sc of ferromagnetic clusters increase almost monotonically along the ingot (NFe=(0.8-1.5)*1019 cm-3, Nc=(1-4)*1015 cm-3 and Sc=200-1000). Experimental results are discussed in the framework of the model of the electronic structure rearrangement with doping [4], assuming the pinning of the Fermi level by the resonant iron impurity level and varying magnetic activity of Fe ions with doping.