Magnetic properties of RFe11.3Nb0.7 compounds (R = rare earth)

Structural and magnetic properties of RFe11.3Nb0.7 compounds with rare-earth elements (R=Y, Sm, Gd, Tb, Dy, Ho, and Er) have been investigated. The Curie temperature increases for R=Sm-Gd, then decreases from R=Gd to Er. In the compound with R=Tb, with increasing temperature, a spin reorientation from an easy magnetization direction in the plane to an easy cone occurs at 365 K. In the compound with R=Er, a spin reorientation from easy plane to easy axis is found at about 40 K. Two spin reorientations take place in the compound with R=Dy, from easy plane to a complex structure at 125 K and from complex structure to easy axis at 210 K. At room temperature, the easy magnetization direction is along the c axis for R=Y, Sm, Gd, Dy, Ho, and Er, and in the plane for R=Tb. Studies of the magnetic anisotropy in YFe11.3Nb0.7 and GdFe11.3Nb0.7 point out that the Fe sublattice anisotropy is of easy axis type. In HoFe11.3Nb0.7, a first-order magnetization process takes place below 150 K when an external magnetic field is applied along the hard magnetization direction. The exchange-interaction constants J(R-Fe) decreases with increasing atomic number of R, as is generally found in rare-earth transition-metal compounds. (C) 1999 American Institute of Physics. [S0021-8979(99)56908-9].