Magnetocrystalline anisotropy in R(Fe,Co)11.3Nb0.7 compounds with R = Dy and Er

Abstract

Magnetic properties, specially magnetocrystalline anisotropy, of the Re(Fe1-xCox)11.3 Nb0.7 compounds (R = Dy and Er) have been investigated by x-ray diffraction (XRD) and magnetic measurements. All the compounds studied crystallize in the ThMn12-type structure for x0.3. Substitution of Co for Fe leads to a monotonic increase of Curie temperature and an obvious decrease of a and c lattice parameters in both Dy(Fe,Co)11.3Nb0.7 and Er(Fe,Co)11.3Nb0.7 compounds. The composition dependence of the saturation magnetization MS at 5 K shows a maximum at x = 0.2 and x = 0.15 in Dy(Fe1-xCox)11.3Nb0.7 and Er(Fe1-xCox)11.3Nb0.7 compounds, respectively. The easy magnetization direction (EMD) at room temperature has been determined by XRD of magnetically aligned samples. Both ac susceptibility and magnetization measurements indicate that as the temperature decreases from 300 K to 5 K, the EMD of all the Er(Fe,Co)11.3Nb0.7 compounds changes from c-axis to a cone whereas the EMD of the Dy(Fe1-xCox)11.3Nb0.7 compounds goes from c-axis, passing through a cone, to a plane for x0.2 and from c-axis to a plane for x0.25. A tentative spin phase diagram is constructed for Dy(Fe1-xCox)11.3Nb0.7 and Er(Fe1-xCox)11.3Nb0.7 compounds with x0.3, respectively.