High coercivity and spin reorientation transition in DyCo10Mo2-xVx compounds

DyCo10Mo2-xVx compounds (x = 0, 0.5, 1.0, 1.5, 2.0) with the ThMn12 structu re were prepared by means of arc-melting and subsequent vacuum annealing. T he magnetic properties were investigated by X-ray diffraction on fixed alig ned powder samples and by magnetization measurements. The lattice constants decrease linearly with increasing x, according to Vegard's law. The easy m agnetization direction of all samples is parallel to the c-axis at room tem perature. The magnetization hysteresis loops of the aligned sample at a ver y low temperature after this sample was cooled under an applied field and z ero held are different. It results from the large coecivity at low temperat ure and magnetization reversal when passing the compensation temperature in the cooling process. After analyses, it is found that the samples are not magnetized to full saturation at 10 K due to the relatively small applied f ields from -5 to 5 T. At least two or three types of particles with much di fferent coercivity coexist in every sample, and the maximum coercivity for at least one of the types is larger than 5 T. The smaller the value of x, t he larger the coercivity in the DyCo10Mo2-xVx compounds. Temperature depend ence of the magnetization indicates that a spin reorientation transition oc curs, and the transition temperature increases from similar to 30 K (for x = 0) to similar to 40 K (for x = 2). The influence of substitution of Mo an d V in Co positions of the 1:12 structure on the magnetic coupling constant and crystalline electric field parameter is discussed. (C) 1999 Published by Elsevier Science B.V. All rights reserved.