Rapidly quenched Sm(CobalCu0.08Fe0.22Zr0.02)8.5 (Cu-/Fe-rich) and Sm(CobalCu0.05Fe0.10Zr0.03)8.5 (Cu-/Fe-poor) ribbons have been prepared by means of the melt-spinning technique. By applying an appropriate annealing procedure a microstructure similar to that of sintered magnets can be obtained. The energy dispersive x-ray microanalysis of the compositional dependence near the cell boundaries suggests a model for the profile of the crystal anisotropy constants responsible for the magnetic hardening. The Cu-/Fe-rich alloy shows a normal temperature dependence of coercivity with a negative temperature coefficient, but the Cu-/Fe-poor ribbons show a positive temperature coefficient in the temperature range from 400–700 K. The different temperature coefficients are discussed in terms of a pinning model.

Intrinsic magnetic properties of RFe10Mo2 compounds (where R = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er or Tm Kou, X.C.; Grossinger, R.; Wiesinger, G.; Liu, J.P.; de Boer, F.R.; Kleinschroth, I.; Kronmuller, H.

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Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and magneto-optical Kerr effect have been used to characterize different crystallization states of melt-spun Co80B20 alloys. The microstructures have been prepared by isothermal annealing at temperatures of TA=325–600 °C for different annealing times. Samples annealed for ta=30 min show an onset of the crystallization at annealing temperatures TA less than 325 °C with the primary precipitation of both face-centered-cubic Co and hexagonal close-packed Co embedded in the amorphous matrix. By HRTEM it is revealed that Co grains with ordered as well as highly distorted lattices are formed, whereby a characteristic feature of the latter are stacking faults. The following step is the formation of orthorombic Co3B with an average grain size of 7.6 μm and of nanocrystalline Co grains, whereby still some amorphous phase is present. Fully crystallized samples were obtained for annealing temperatures higher than 412 °C (ta=30 min). The decomposition of the large-grained Co3B in nanocrystalline, body-centered tetragonal Co2B and Co starts at temperatures of TA>400 °C. The volume fraction and average grain size of the remaining Co3B decreases with increasing annealing temperature, whereas the Co2B grains show the opposite behavior. After a long time annealing for seven days at temperatures higher than 550 °C, the microstructure consists of fcc-Co grains with facet-like morphology and Co2B, but no Co3B have been detected.

The study of the effect of Ga substitution on the magnetic properties of arc-melted Sm2Co17−xGax (x=0–7) compounds has been carried out by means of x-ray diffraction (XRD) and magnetic measurements. XRD patterns show that all samples of Sm2Co17−xGax (x=0–7) crystallize in the rhombohedral Th2Zn17-type structure. The Ga substitution for Co leads to an approximately linear decrease in the Curie temperature and a rapid decrease in the saturation magnetic moment which is faster than that in the case of magnetic dilution. Spin-reorientation transition is observed for Sm2Co11Ga6 compound at 32 K. In order to determine the room-temperature easy magnetization direction (EMD), XRD measurements are performed on magnetically aligned samples with x⩽5. The result shows that the EMD of these compounds corresponds to the c axis. The anisotropy constants K1 and K2 of Sm2Co17−xGax compounds were derived by fitting the hard-direction magnetization recoil curves measured on magnetically aligned powder samples as well as by fitting the magnetization recoil curves measured on polycrystalline bulk samples. The fitting results indicate that the substitution of Ga for Co in Sm2Co17 compound decreases the anisotropy constants, thus indicating the weakening of the easy-axis anisotropy.