A study of the magnetocrystalline anisotropy of RFe11-xCoxTi compounds with R = Y and Er

Structural and magnetic properties of the RFe11-xCoxTi compounds with R = Y and Er have been investigated. X-ray diffraction patterns and thermomagnet ic curves show that all the synthesized compounds with x ranging from 0 to 11.0 are almost single phase and crystallize in the ThMn12-type structure. Substitution of Co for Fe leads to a monotonic decrease of lattice constant s and unit-cell volume and a clear increase of the Curie temperature. The s aturation moments increase with increasing Co content, going through a maxi mum at around x = 2.5, and then decrease with further increasing Co content . The easy magnetization direction (EMD) at room temperature for ErFe11-xCo xTi compounds is along the c-axis for x less than or equal to 4, perpendicu lar to the c-axis for 6 less than or equal to x less than or equal to 9 and then back to the c-axis for further increasing x. The anisotropy of the YF e11-xCoxTi compounds shows a similar behaviour. This concentration dependen ce of the magnetocrystalline anisotropy in the YFe11-xCoxTi and ErFe11-xCox Ti compounds results from the different contributions to the magnetocrystal line anisotropy from various transition-metal sites and the preferential oc cupation of Co atoms. A spin reorientation occurs below the Curie temperatu re for all ErFe11-xCoxTi compounds. Spin reorientation temperatures as a fu nction of Co concentration were derived. A tentative spin phase diagram is given for ErFe11-xCoxTi compounds and can be understood in terms of crystal field theory.