Magnetic properties and formation of Sr ferrite nanoparticle and Zn, Ti/Ir substituted phases

Strontium hexaferrite nanoparticles are prepared by the chemical sol-gel route. Specific saturation magnetization sigma (s) and coercive field strength H-c are determined depending on the heat treatment of the gel and iron/strontium ratio in the starting solution. These ultrafine powders with single-domain behavior have specific saturation magnetization sigma (s) = 74 emu/g and coercive field strength H-c = 6.4 kOe. Experimental results show that it is necessary to preheat the gel between 400 and 500 degreesC for several hours. It can prevent the formation of intermediate gamma -Fe2O3 and help to obtain ultrafine strontium ferrite single phase with narrow size distribution at a low annealing temperature, Additionally, the magnetic properties of sol-gel derived strontium ferrite with iron substituted by Zn2+, Ti4+ and Ir4+ are discussed. For an amount of substitution 0 <x less than or equal to0.6, the (Zn,Ti)(x) substituted strontium ferrite shows higher values of both coercive field strength and saturation magnetization than the (Zn, Ir)(x) substituted phase. (C) 2001 Elsevier Science B.V. All rights reserved.