AN UNIDENTIFIED MAGNETIC TRANSITION IN R2FE14X COMPOUNDS (R = SM, TB, DY, HO, ER, AND TM - X = B OR C)

In Ho2Fe14B and Ho2Fe14C the temperature dependence of the ac initial susceptibility between 4.2 and 300 K shows two peaks. The peak at the lower temperature can be explained by a well-known spin reorientation transition (at 62 K for Ho2Fe14B and at 40 K for Ho2Fe14C). The peak at the higher temperature (at 245 K for Ho2Fe14B and at 265 K for Ho2Fe14C) disappears when the external field is applied parallel or perpendicular to the preferential direction of a magnetically aligned sample. The similar peak was also traced for R2Fe14X compounds (R = Sm, Tb, Dy, Ho, Er, and Tm; X = B or C). Searching for the nature of this peak traced by measuring the temperature dependence of the ac susceptibility for 3d-4f compounds is still under progress.